Analysis of Corneal Refractive Power Following SMILE Procedure

Analysis of Corneal Refractive Power Following SMILE Procedure | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Analysis of Corneal Refractive Power Following SMILE Procedure Congcong Sun, Siyu Song, Tao Jin, Xiujin Guo, Bing Zhang, Chunmei Tong This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-8602154/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Objective The main purpose of this study is to investigate the changes of corneal focusing ability after SMILE surgery. We used various measurement methods and collected a lot of information to study this problem. The results of the study aim to provide specific details to help ophthalmologists choose the most suitable intraocular lens for those who have cataract and have undergone vision correction surgery before. Methods From September 2020 to January 2021, we conducted a clinical study on 37 people (70 eyes) who had undergone SMILE surgery in Myopia Laser Treatment Center of our hospital. All participants came back for reexamination within three months after the operation. We made a comprehensive examination before and after the operation, including subjective and objective optometry, IOLMaster biometrics and Pentacam anterior segment imaging. Pentacam equipment generated data of SimK, TNP and TCRP, and equivalent corneal curvature readings (EKR) with diameters of 3 mm, 4 mm and 5 mm, and each measurement was centered on the pupil. The Km value is obtained from the evaluation of IOL Master. We compared and analyzed the refractive changes (△SimK, △TNP, △TCRP, △EKR and △Km) after operation with the refractive changes (△SE) on corneal surface. SPSS 22.0 software is used for statistical processing, including Kolmogorov-Smirnov test to see whether the data is normally distributed, variance analysis, paired t test and Pearson correlation analysis. Results According to SMILE procedure, the measurement results of TCRP4 mm and EKR4.5 mm remained stable, and no obvious changes were found (P > 0.05). There was no obvious relationship between the change of TCRP4 mm (△TCRP4 mm) and the change of spherical lens degree (△SE) (P > 0.05). However, there is a strong correlation between △TCRP4 mm and △SE, and the correlation coefficient is r = 0.989. In addition, the consistency among △TCRP5 mm, △TCRP4 mm and △SE is also very high, and the 95% consistency ranges from − 0.47 to 0.11 D and − 0.32 to 0.50 D respectively. Conclusion Although Pentacam is the most accurate method for measuring TCRP4mm after corneal refractive surgery, it requires further verification and improvement before it can be widely used in combination with the existing intraocular lens calculation formula. Refractive outcomes following corneal refractive surgery simulated keratometry indices calculation of true net power assessment of equivalent keratometry total corneal refractive power measured by ray tracing Figures Figure 1 Figure 2 Figure 6 Figure 7 Preface Corneal refractive surgery has been common in China for more than 20 years. Technical progress has continually improved surgical methods. The field has advanced from early PRK to LASIK and then to personalized LASIK based on wavefront aberrations and corneal topography. Since 2011, the clinical use of SMILE has changed the landscape of traditional corneal-refractive surgery. SMILE differs from older methods that require corneal flaps. It was quickly adopted in China because of its advantages, such as reduced trauma and rapid corneal healing [ 1 – 3 ]. SMILE is currently the most advanced technology for this type of surgery. However, patients who undergo this surgery eventually develop age-related cataracts. Corneal refractive surgery has been widely performed in China for two decades. The technology in this field is constantly advancing and improving. The field has developed rapidly, from methods such as photorefractive keratectomy (PRK) to modern laser surgery. Post-refractive surgery cataract patients who undergo intraocular lens power calculations using standard corneal refractive measurements frequently end up with hyperopic outcomes following their procedure, as documented in multiple clinical studies [ 4 – 9 ].As more people undergo this surgery, an accurate and reliable evaluation of corneal refractive power is needed. Before slit-scanning technology, doctors could not obtain data from the back of the cornea. They could only measure the anterior surfaces. Corneal refractive surgery has been widely performed in China for more than 20 years. Technical progress has improved surgical outcomes. The field has advanced rapidly from PRK to the current laser surgery. The calculation of the corneal diopter depends on a set relationship between the anterior and posterior cornea. Devices such as the standard corneal curvature meter, corneal topographic map system, and IOL Master aid in these measurements. The IOL Master is a common tool used in cataract surgery. It accurately measures the corneal diopter for normal corneas. However, measurement errors may occur if the corneal structure changes [ 6 , 10 , 11 ]. The IOL Master measures corneal diopters, similar to the traditional corneal curvature meter. It uses Gullstrand's model eye and the formula K = (n1)/r to quantify the mean curvature of the front surface. To determine the focusing capability of the cornea, we employed a theoretical relationship, presuming that the back curve measures 82% of the front one, while using a conventional light-bending constant of 1.3375 [ 12 ].However, the cornea has both anterior and posterior surfaces that are not flat. Some question whether this assumption leads to accurate results [ 8 – 9 ]. With the new topographic measurement technology, doctors can examine both the anterior and posterior corneal surfaces. These tools simultaneously capture curvature data from both surfaces. There is no longer a need to assume a fixed relationship between the two surfaces to calculate the corneal refractive power. Examples of these devices include Pentacam, Sirius, Galilei, and Orbscan.Pentacam is an advanced 3D diagnostic tool, which is specially used to examine the front of the eye [ 14 – 17 ]. It adopts Scheimpflug imaging technology and collects data by rotation. Pentacam is famous for its high accuracy and rich information, which can comprehensively evaluate the eye structure. It can calculate the shape of the anterior and posterior corneal layers, the overall corneal thickness and optical characteristics. This equipment provides about 40 different indexes, which are used to analyze the focusing ability of cornea and realize in-depth examination. In order to draw the optical power of cornea, Pentacam uses many methods, including SimK based on projection readings, TNP calculated by Gaussian lens theory, TCRP determined by ray modeling, and EKR providing standardized corneal curvature readings. These assessment techniques examine different ranges from 1 mm to 8 mm through overall and segmented analysis. The measurement can be aligned based on the pupil center point or the corneal vertex. Many previous studies have compared SimK, TNP, TCRP, and EKR in various corneal refractive surgeries, including LASIK, LASEK, and PRK. Research has generally shown that TCRP can most accurately reflect corneal refractive power after surgery. Corneal features may differ between ethnic groups; however, few studies have evaluated these methods before and after SMILE in Chinese patients. Therefore, careful selection and analysis of SMILE patient data in China is very important. This will help us identify the most effective and accurate method for measuring corneal refractive power in Chinese patients. In this study, we used SimK, TNP, TCRP, EKR, and K-means to measure the corneal refractive power before and after SMILE. The methods were evaluated to determine the optimal accuracy for patients with cataracts after post-refractive corneal surgery. Materials and Methods 1. Research subjects 1.1 Inclusion criteria To participate in this study, you must be at least 18 years old. Prescription stability for glasses or contact lenses is required over the prior 24-month period.The degree of myopia should be between − 1.00 and − 8.00. Your corrected vision with glasses or contact lenses must be 20/25 or better. If you wear soft contact lenses, stop using them at least 14 days before the appointment. For hard contact lenses, stop using them for a full month. Your intraocular pressure should be between 10 and 21 mmHg. You should not have eye conditions such as early keratoconus or severe corneal scarring. You should not have health problems such as diabetes, keloids, depression, or connective tissue diseases. 1.2 Inclusiostatus As From September 2020 to January 2021, 37 people (70 eyes in total, 37 right eyes and 33 left eyes) underwent SMILE surgery at our myopia laser treatment center. All patients were re-examined three months after the operation. This group comprised 20 men and 17 women, with an average age of 26.3 ± 5.2 years (range: 18–40 years). Before the operation, their average spherical equivalent diopter was (-4.58 ± 1.36)D, ranging from − 7.2 D to -1.75 D. After the operation, the spherical lens diopter ranged from − 1.50 D to -0.75 D, with an average of (-0.10, 0.44) D. 2. Research methods 2.1 Preoperative and postoperative examinations 2.1.1 Basic examination 1) Visual acuity: Before and after the operation, we used a standard eye chart to check the vision of each patient without glasses and their best vision after wearing them. 2) Optometry: We performed subjective and objective optometry examinations before and after the operation. These included testing with natural and dilated pupils. 3)Intraocular pressure (IOP): The intraocular pressure was measured three times using a non-contact intraocular pressure meter, and a final average result was calculated. 4) Slit lamp: A slit lamp microscope was used to examine the corneal condition before and after surgery. 5) Fundus: The fundus was examined using a direct ophthalmoscope and three-mirror contact lens to exclude fundus diseases. If necessary, fundus laser treatment was performed. 6) 6) Corneal thickness: To anesthetize the eye surface, we applied a drop of 0.4% proparacaine hydrochloride to the lower eyelid conjunctival sac. Using the Pachmate ultrasonic thickness gauge, we took five consecutive measurements at the coneal center and recorded the lowest reading each time. 2.1.2 Examination with Pentacam HR Three-dimensional Anterior Segment Analyzer The German-manufactured Pentacam HR employs the Scheimpflug principle as a 3D analyzer of the anterior segment.By rotating the crack beam, it can take 50 crack images at different angles from 0 to 180 degrees in 2 seconds.This method will collect data from a total of 138,000 points on the anterior and posterior surfaces of the cornea. The final result is a complete topographic map evaluation of the anterior and posterior parts of the cornea, including detailed schematic diagrams of tangential curvature and axial curvature. These images can highlight important corneal features, such as eccentric position, central radius of curvature and astigmatism. This method improves the accuracy of reading in the central area, and can also determine the curvature data of selected points on the anterior and posterior surfaces of the cornea. Operating steps: In a dark environment, ask the patient to put his chin and forehead in a fixed position on the designated bracket. Instruct the patient to stare at a static red dot. When it is clearly focused, the system will automatically start scanning the eyes. The scanning should be repeated three times in total, and only the scanning results that meet the image quality standards will be adopted. All measurements are carried out by professional technicians.The data collected by Pentacam HR included corneal central readings with diameters of 3, 4, and 5 mm, centered on the pupil, including SimK, TNP, TCRP, and 4.5 mm EKR. 2.1.3 Examination by IOL Master The working principle of IOLMaster uses corneal reflection to measure the size of the image reflected by six light spots projected from the front surface of the cornea, evenly distributed on a circle with a diameter of 2.3 mm. The distance between the reflected light points must be calculated. According to Gullstrand's model eye formula k=(n-1)/r, this instrument can only measure the average curvature of the anterior surface of the cornea. Assuming that the ratio of the curvature radius of the posterior surface to that of the anterior surface of the cornea is 82% and the standard refractive index is 1.3375, the refractive power of the cornea can be calculated. The measurement steps were as follows: the patient was instructed to lean his chin and forehead against the designated bracket while staring at a target point on the equipment. IOL Master will measure K1 and K2, respectively, and the final value (Km) is the average of three consecutive measurements; the calculation formula is Km = (K1 + K2)/2. The data collected by the IOL Master were Km. 2.2 Surgical methods All steps were completed by the same experienced surgeon. We instructed the patient to use gatifloxacin eye drops four times a day for three days before the operation to prevent infection. The same regimen was continued postoperatively. Before the operation, a drop of 0.4% proparacaine hydrochloride eye drops was instilled into the conjunctival sac for local anesthesia. The conjunctival sac was then washed with warm saline, and the skin around the eyes was disinfected with a cotton swab dipped in 0.5% povidone-iodine. Disinfection is centered on blepharoptosis, from the inside out, ranging from the hairline to the line connecting the nasolabial groove and the earlobe, crossing the nasal midline inward. The disinfection process was repeated three times. After standard disinfection, a corneal flap and matrix lens were created using the VisuMax femtosecond laser system (Carl Zeiss, Germany). The laser parameters were set as follows: pulse energy is 140nJ, pulse frequency is 500kHz, corneal flap thickness is 120um, flap diameter, 7 mm; lens diameter is 6-6.5 mm, substrate thickness increased by 10-15um, lateral incision, 2 mm; and angle of lens and small incision, 90 °. The patient lies on his back on the operating table, with his head straightened to ensure that his forehead and jaw are at the same level and that the line from the jaw to the bridge of the nose is centered on the midline. After administering topical anesthesia, the patient was asked to gaze directly at the light above. The position of the corneal reflection point relative to the pupil center was recorded and remembered. Before making the lens, the green fixation light was adjusted to the reflection point. The device was then slowly allowed to contact the cornea until 80% contact was achieved, and negative-pressure suction was initiated. The front and back surfaces of the lens were scanned at the incision site using a femtosecond laser. The lens was gently and quickly separated and removed through a small incision after complete separation. Check whether the lens is complete. Finally, the corneal flap bed was washed with a balanced salt solution, and the excess liquid was removed with a sterile sponge to complete the operation. 2.3Assessment of Variations in Corneal Refractive Power Following Small Incision Lenticule Extraction (SMILE) Procedure: A Comparative Analysis of Preoperative and Three-Month Postoperative Measurement Outcomes 2.3.1 Refractive changes in the corneal plane (△SE) To calculate the correction, we converted the degree of the glasses plane to the degree of the cornea plane, assuming that the lens was 12 mm from the cornea during the test. The difference in the corneal plane degree before and after the operation is the refractive change brought about by the SMILE operation, that is, the amount of corneal plane refractive state change after the operation. Spherical equivalent (SE) = spherical diopter + 0.5 × cylindrical diopter For the conversion of preoperative and postoperative spectacle-plane equivalent spherical power (SE) to corneal-plane equivalent spherical power (MR), the formula MR = SE / (1–0.012 × SE) was used. Surgical corneal refractive power shift (ΔSE): ΔSE = preoperative MR - postoperative MR 2.3.2 The corneal refractive power Km was obtained using the IOL Master, and the simulated corneal refractive power ( SimK) was obtained using Pentacam. Similar to the traditional keratometer, Km in the IOL Master and SimK in Pentacam are based on Gullstrand's schematic eye. These devices regard the cornea as a thin lens and can only measure the average curvature of the front surface. They assumed that the ratio of the posterior to anterior radius of curvature was fixed at 82% and then calculated the corneal refractive power using a standard refractive index of 1.3375. K = (n − 1)/R(1) Here, n = 1.3375, and the refractive index of air is 1.00. R represents the radius of curvature of a specific area on the anterior surface of the central cornea (in meters). The difference lies in the measurement method: the IOL Master calculates corneal refractive power (Km) by taking six points on a circle with a diameter of 2.3 mm. In contrast, Pentacam was used in this study to determine the corneal refractive power (Simk) from measurements at 3, 4, and 5 mm from the center of the cornea. The basic principle of TNP in Pentacam is to imagine the cornea as a thick lens. This method uses the “paraxial approximation” calculation method and assumes that light propagates to the posterior surface of the cornea in parallel. By assuming that light passes through the front and back surfaces of the cornea in parallel, they used the Gaussian optical formula (which is specifically used to calculate thick lenses) to calculate the total refractive power of the entire cornea. K=(n1-n)/r1+(n2-n1)/r2 (2)​ In this context, air possesses a refractive index of n0 = 1, whereas the actual refractive indices of the cornea and aqueous humor are n1 = 1.376 and n2 = 1.336, respectively. The curvature radii for the anterior and posterior corneal surfaces are denoted by r1 and r2, respectively, with the reference plane established at the second principal plane anterior to the cornea. 2.3.3 Total corneal power (TCRP) based on the tracy-tracing method The TCRP principle in Pentacam uses ray tracing, which tracks the path of a parallel incident light beam through the anterior and posterior surfaces of the cornea, according to Snell's law. The focusing distance was measured and converted to corneal diopters. K = n/f (3) In this case, n was equal to 1.336, f represented the focal length, and the reference plane was the anterior surface of the cornea. 2.3.4 Equivalent keratometry reading (EKR) In 2006, Oculus and Holladay jointly launched the Pentacam Holladay report, which was specifically used to evaluate the corneal refractive power of patients with cataracts who had undergone corneal refractive surgery. This adjustment can make the K value measured by Pentacam compatible with the traditional intraocular lens power calculation formula. The specific algorithm is as follows. EKR(D)=(n1-1)Ra+(n-1)(1–1/R2)×R1/Rp ༈4༉ It can be simplified as: EKR = 0.376/Ra − 0.03165/Rp。 (5) The refractive index of the cornea is n1 = 1.376, which differs from the standard value of n = 1.3375. Meanwhile, Ra denotes the curvature radius of the front corneal surface, and Rp denotes that of the rear surface. For our investigation, we focused on a 4.5 mm central zone of the cornea, known as the EKR. 2.4 Statistical analysis Statistical analysis was conducted using SPSS version 22.0, with continuous variables presented as means ± standard deviations. To assess the normality of distribution for all continuous variables, we employed the Kolmogorov-Smirnov test.Because the p-value is greater than 0.05, the data are normal and can be tested using parametric tests. We used repeated-measures ANOVA to compare differences in Km, EKR4.5 mm, Simks, TNPs, and TCRPs before and after the operation, and then used the Bonferroni method for post hoc comparisons. In GraphPad Prism, the same letter in a column indicates no difference, and different letters indicate a difference in significance. A paired T-test was used to compare the changes in diopter (△ SE) and corneal curvature (△ K) before and after the operation. Statistical significance was set at p < 0.05.The consistency of ΔSE and ΔK was analyzed using the Bland-Altman method, and the deviation was expressed as 95% limits of agreement (LoA). The Pearson correlation analysis revealed a significant association between the two datasets, with a p-value less than 0.05. Results 1. General results Thestudyanalyzed70eyesfrom37patents(37right、33left)comprising20menand17womer、withationage from 26.35. 2years(range,18-40).The spherical equivalent (SE) values at the corneal plane were -5.04±1.33 D and 0.12±0.31 D, respectively. The change in refractive status (△SE) at the corneal plane before and after surgery was 4.92±1.14 D. 2. Differences in corneal refractive power obtained by different methods before surgery Preoperatively, the values of EKR4.5mm, Simk 3 & 4 & 5 mm, TNP 3 & 4 & 5 mm, TCRP 3 & 4 & 5 mm measured by Pentacam and Km measured by IOL Master were 43.21±0.64D, 43.52±0.64D, 43.46±0.64D, 43.43±0.65D, 42.25±0.67D, 42.15±0.66D, 42.05±0.67D, 42.89±0.67D, 42.93±0.66D, 43.06±0.67D and 43.68±0.63D, respectively. Through the statistical analysis of pairwise comparison, it was found that there were obvious differences in corneal refractive power measured by different preoperative methods (ANOVA: P<0.05). Specifically, the measured values of Km and Simks are the highest, EKR4.5 mm and TCRPs are in the middle, and TNPs is the lowest (P < 0.05). The analysis further shows that there are considerable differences between Km, EKR4.5 mm and Simks, TNPs and TCRPs, and all these pairs show obvious differences (P 0.05). The measured values from 3 mm, 4 mm and 5 mm regions also showed no statistically significant difference (P > 0.05) (Table 1 and Figure 1). 3. Differences in corneal refractive power obtained by different methods at 3 months after surgery Three months after the surgical intervention, a series of parameters related to corneal refractive power were evaluated using two different clinical measurement instruments, namely the Pentacam and IOL Master systems. Specifically, parameters such as EKR4.5mm, △Simk (3, 4, 5 mm), △TNP (3, 4, 5 mm), △TCRP (3, 4, 5 mm), were quantified via the Pentacam system, while the Km parameter was determined through the IOL Master device. The measured values of these parameters were recorded as follows: EKR4.5mm was 38.52 ± 1.16 diopters (D), Simk3mm was 39.41 ± 0.92D, Simk4mm was 39.39 ± 0.93D, Simk5mm was 39.40 ± 0.90D, TNP3mm was 37.66 ± 1.07D, TNP4mm was 37.59 ± 1.04D, TNP5mm was 37.60 ± 1.01D, TCRP3mm was 37.71 ± 1.07D, TCRP4mm was 37.93 ± 1.09D, TCRP5mm was 38.32 ± 1.07D, and the Km value was 39.51 ± 1.03D respectively. Subsequent pairwise comparison analysis was conducted to examine the differences in corneal refractive power values derived from the distinct measurement methods at three months postoperatively. The analysis of variance (ANOVA) results indicated statistically significant disparities in corneal refractive power measurements obtained using various methodologies (ANOVA: P < 0.05). Among the measured parameters, Km had the largest value. This was followed, in descending order, by the Simk series of parameters, the EKR4.5 mm parameter, and the TCRP series of parameters, whereas the TNP series of parameters had the smallest values; all differences were statistically significant (P < 0.05). A systematic comparison among individual parameter groups yielded the following finding: No significant disparity was noted between the Km value and the SimK parameter group, with a p-value greater than 0.05. However, notable differences were observed between Km and other preoperative corneal metrics, with a P-value below 0.05. Similarly, the EKR4.5 mm parameter showed no statistical variation in the TCRP group (P > 0.05), but distinct differences were noted when compared with other preoperative refractive power measurements (P 0.05) but significant differences with other parameters (P 0.05), while they exhibited significant differences from other preoperative measurements (P 0.05), but they did show significant differences with other corneal measurements (P 0.05).( Table 2 and Figure 2). 4. Variations in the relationship between changes in corneal curvature (△K) and shifts in refractive power at the corneal plane (△SE) before and after surgical intervention Three months after the surgical procedure, the corneal curvature (K) value showed a notable reduction from the preoperative baseline, with a statistically significant difference (P < 0.05). The changes in corneal refractive power before and after surgery, including △EKR4.5mm, △Simk/TNP/TCRP 3/4/5mm, and △Km, were 4.69 ± 1.13D, 4.11 ± 1.00D, 4.07 ± 0.97D, 4.03 ± 0.90D, 4.59 ± 1.17D, 4.56 ± 1.12D, 4.45 ± 1.05D, 5.18 ± 1.14D, 5.01 ± 1.10D, 4.75 ± 1.12D, and 4.17 ± 1.06D, respectively. The differences between these values and △SE were -0.23 ± 0.42D, -0.81 ± 0.49D, -0.85 ± 0.45D, -0.89 ± 0.30D, -0.33 ± 0.37D, -0.36 ± 0.48D, -0.47 ± 0.24D, 0.26 ± 0.39D, 0.09 ± 0.21D, -0.18 ± 0.15D, and -0.75 ± 0.36D, respectively. When analyzing the correlation between changes in corneal curvature (△k) derived from various measurement techniques before and after surgery and the corresponding changes in spherical equivalent refraction (△SE), our findings indicated that the discrepancy between △TCRP4mm and △SE was the only one that did not reach statistical significance. 5. Correlation analysis of changes in corneal curvature (△K) and refractive power variations at the corneal plane (△SE) preoperatively and postoperatively There were positive correlations between ΔEKR 4.5, ΔSimk 3/4/5, ΔTNP 3/4/5, ΔTCRP 3/4/5, ΔKm with △SE (r = 0.933, 0.982, 0.978, 0.981, 0.948, 0.975, 0.947, 0.985, 0.989, 0.983, 0.950, all P < 0.01). The highest correlations were observed between △TCRP 3 mm, △TCRP 4 mm, △TCRP 5 mm, and △SE (r = 0.985, r = 0.989, and r = 0.983, respectively) ( Table 4). 6. Analysis of the Consistency between the Alteration in Corneal Curvature (△K) and the Variation in Refractive Power at the Corneal Plane (△SE) Pre - and Post - surgery In addition, we computed and determined the 95% limits of agreement for a series of different parameters, including △EKR 4.5 mm, △Simk 3-5 mm, △TNP 3-5 mm, △TCRP 3-5 mm, △Km, and △SE. Specifically, the 95% agreement range for △EKR 4.5mm was from -1.05 to 0.59 diopters (D); for △Simk 3mm, it was within -1.77 to 0.15 D; for △Simk 4mm, it spanned from -1.73 to 0.33 D; for △Simk 5mm, it was between -1.48 and 0.30 D; for △TNP 3mm, it ranged from -1.06 to 0.40 D; for △TNP 4mm, it covered -1.30 to 0.58 D; for △TNP 5mm, it was in the interval of -0.94 to 0.00 D; for △TCRP 3mm, it was between -0.50 and 1.02 D; for △TCRP 4mm, it fell within the range of -0.32 to 0.50 D; for △TCRP 5mm, it was within -0.47 to 0.11 D; and for △Km, it spanned from -1.46 to 0.04 D. Among these difference parameters, △TCRP 5 mm, △TCRP 4 mm, and △SE exhibited particularly high consistency, with their respective 95% limits of agreement being -0.47 to 0.11 D and -0.32 to 0.50 D.( Table 5). Discussion Corneal refractive surgery alters the corneal and anterior segment structures, leading to changes in some parameters that affect the accuracy of existing methods for calculating intraocular lens (IOL) power. Among these factors, the main source of error is the calculation of the corneal diopter [ 18 – 20 ]. Although many techniques are available for accurately measuring corneal diopter after surgery, most rely on indirect estimates based on assumptions and usually require preoperative data. To date, there is no widely accepted method for directly and accurately measuring the corneal diopter after refractive surgery. The ideal solution is to find a technology that can directly measure the true corneal diopter without relying on assumptions or preoperative data and is also compatible with IOL calculation formulas. In recent years, the IOL Master and Pentacam have been widely studied and used in clinics as non-contact examination equipment. Because of their different measurement principles, it is crucial to evaluate the accuracy of their results in the clinic. Based on the principle of corneal curvature measurement, the IOL Master can only measure the average curvature of the anterior corneal surface, with limited sampling points, and is unable to evaluate the central corneal area. Pentacam uses the rotating slit optical scanning method based on Scheimpflug imaging technology, which can generate different corneal curvature measurement data from multiple angles. Regardless of corneal refractive index variations, this technique delivers precise measurements of corneal refractive power, maintaining accuracy even when the anterior and posterior corneal surface curvature ratios are altered or when post-surgical refractive index values become questionable [ 21 – 23 ].In this study, the corneal curvature measured by the IOL Master before and after refractive surgery was compared with that measured using different Pentacam methods. The results showed no statistically significant difference between the IOLMaster Km and SimK values of Pentacam before the operation. This is consistent with the results of Cao et al. [ 24 ], who also found no significant difference between the measured values from SimK and IOL Master at a 3 mm center on Pentacam. However, Elbaz et al. [ 25 ] studied 22 normal eyes (with an average age of 56.3 years) and reported a significant difference between the 3 mm SimK in the center of the Pentacam and the IOL Master Km. Similarly, Pan et al. [ 26 , 13 ] compared the left eyes of 169 college students and found a significant difference between the SimK values of Pentacam and Km values of IOL Master, which is in contrast to our findings. Our findings differ from those of Elbaz et al. and Pan Hong et al., which may be due to differences in age, eyes, myopia, hyperopia, and the number of participants. However, most previous studies focused on normal eyes without corneal refractive surgery, and few have reported comparisons of corneal curvature after surgery using Pentacam and IOL Master. Therefore, this study aims to address this problem. Our results show that there is no obvious mathematical difference between the SimK values measured by Pentacam and the Km values measured by IOL Master after corneal refractive surgery. However, compared with the values of EKR4.5 mm, TNPs, and TCRPs, the differences were large, with average differences of 1.04D, 1.9D, and 1.60D, respectively. We should recognize that if there is a 1D error in measuring the corneal curvature, there will also be a 1D error in calculating intraocular lens power, which is unacceptable in clinical practice [ 27 ]. Therefore, although there is no obvious mathematical difference between the simulated corneal curvature measured by Pentacam and IOL Master after surgery, the difference is more than 1D compared with other K-value measurement methods, which means that the K-values of these two machines cannot be used casually for eyes that have undergone corneal refractive surgery. In the Holiday report, EKR was calculated by further optimizing the Gaussian optical formula, this time using the equivalent refractive power of the cornea in the 4.5 mm area, known as the 4.5 mm EKR. Some studies have compared EKR values with TNP and Simkacrossn in different diameter ranges, as well as with other commonly used clinical methods, such as the clinical history and Shammas methods, and have presented different views. However, to the best of our knowledge, no study has explored the relationship between EKR measurements and TCRP after refractive surgery. Our research includes a 4.5 mm EKR and compares it with the K values obtained using the other four methods. The findings indicated that at the three-month mark, there was no appreciable discrepancy between the 4. mm EKR and TCRPs; however, a substantial difference was noted when compared to other pre-operative corneal measurements. Liu Houcang et al. [ 28 ] obtained the K values for SimK, 4. mmTNP, 5.0 mmTNP, 4.5 mmEKR, the clinical history method, Shammas method, and the Haigis-L method by analyzing data from 121 eyes three months after LASIK/SMILE. They found significant statistical differences between 4.5 mm EKR and SimK and between 4.0 mm TNP and 5.0 mm TNPe, consistent with our findings. The equivalent refractive power was obtained by a secondary adjustment based on the Gaussian optical formula, which accounts for the accurate refractive index of the corneal tissue, corneal thickness, and the influence of the posterior surface. The simulated corneal refractive power only considers the front surface of the cornea and a standard refractive index of 1.3375; however, this is not the actual refractive index. Therefore, a difference exists between the equivalent corneal refractive power and the simulated refractive power after surgery. After corneal refractive surgery, there was no significant statistical difference between EKR4.5 mm and TCRPs, which may be because the corneal surface is not a perfect sphere but an aspheric surface with a steeper center and flatter periphery with spherical aberration. Because the equivalent refractive power and ray-tracing method consider spherical aberration based on the real refractive index, in theory, EKR4.5 mm should be able to reliably estimate the corneal refractive power after surgery. However, there was a significant difference between △EKR4.5 mm and △SE, and the 95% consistency limit was very wide, which indicates that the EKR value of 4.5 mm is not a good index to reflect the changes in corneal refractive power before and after surgery in this study. In this study, we used five methods (SIMK, TNP, TCRP, EKR, and) KMto evaluate the measurement results of corneal refractive power before and after the SMILE operation and compared them with the change in corneal planar refractive power (ΔSE). We found that these five methods yielded different results in evaluating corneal refractive power, among which ΔTCRP4mm was closest to ΔSE, with high consistency and correlation. Many scholars at home and abroad have also used SimK, TNP, and TCRP to evaluate corneal refractive power. Recent research indicates considerable disparities among simulated corneal refractive power (SimK), true net refractive power (TNP) derived from the Gaussian thick lens formula, and corneal refractive power (TCRP) gleaned through ray-tracing techniques in both unoperated and surgically altered eyes. Simulating corneal refractive power often overestimates it after surgery [ 21 , 22 , 23 , 30 – 35 ], whereas corneal curvature (TCRP) calculated by ray tracing accurately reflects the refractive changes caused by the excimer laser [ 34 – 37 ], consistent with our findings. Our study found that the value measured by TCRP before the operation was approximately 0.5 D lower than that measured by SimK. Current studies have shown that Simk and TCRP values differ in both normal eyes and eyes that have undergone refractive surgery, with Simk being consistently higher. Savini et al. [ 38 ] said that the TCRP measured by Sirius in normal eyes was 0.6 D, lower than that of Simk. Hirayama et al. [ 39 ] also found that Simk was 0.4 D higher than TCRP when measured with Galilei. Three months after the operation, the TCRP was approximately 1.4 D lower than SimK, which was similar to the result reported by Huo et al.. [ 29 ]. They found that the TCRP was 1.75 D lower than Simk in eyes undergoing refractive surgery. The main difference between these two methods arises from two key aspects. First, they used different refractive indices. Simk was calculated according to Gullstrand's standard eye model, using a standard refractive index of 1.3375. This model assumes that the anterior-to-posterior corneal curvature ratio is fixed at 82% and that the corneal thickness is 500 microns. Once the fixed relationship between these curvatures is altered, this method becomes imprecise. In contrast, the TCRP uses ray tracing, which applies Snell's law to trace the paths of parallel rays passing through the anterior and posterior surfaces of the cornea. It first measures the focal length, then converts the focal length into corneal refractive power, and uses the actual refractive index (air: 1, cornea: 1.376, aqueous humor: 1.336), thus avoiding reliance on a hypothetical corneal refractive index when calculating curvature. Second, the reference planes differ. Simk calculation regards the cornea as a thin lens and defines its refractive power at the posterior vertex of the cornea. In contrast, takes the anterior surface of the cornea as the reference plane, and both the anterior and posterior surfaces of the cornea are considered in the comprehensive analysis. Our study found that TNP's performance in evaluating corneal refractive surgery was suboptimal, consistent with previous research [ 21 , 30 , 31 , 34 ]. In addition, TCRP was higher than TNP before and 3 months after surgery. Qian et al. [ 31 ] studied the data on SimK, TNP, and TCRP from 144 patients who underwent SMILE, and found that TCRP was higher than TNP before and 6 months after the operation. The difference between the TCRP and TNP is that they use different refractive reference surfaces. The TCRP references the anterior surface of the cornea, whereas the TNP uses the second principal plane anterior to the cornea. In addition, Gaussian optics operates as a streamlined framework that employs the paraxial approximation while mistakenly treating rays as parallel at the rear surface—a flawed premise given that these beams have already undergone refraction at the front surface and anything but remain parallel to it. Moreover, this discrepancy becomes particularly pronounced following myopia-corrective procedures, where alterations in corneal thickness coupled with the modified ratio of anterior to posterior curvature radii impact Gaussian optics to a far greater extent than they do ray-tracing methodologies [ 34 ].Notably, our research found that the TCRP performance in the 4 mm area was better than that in other measurement ranges. This result is consistent with the principle of the average value of the central 4 mm area used by Galilei in the default calculation formula for intraocular lens power. Similarly, Qian et al. [ 31 ] reported similar results. They found that the annular TCRP values of 3 mm and 4 mm were closer to ΔSE than to ΔSimK, ΔTNP, and ΔTCRP six months after the SMILE operation. Gyldenkerne et al. [ 35 ] studied 410 eyes operated with SMILE and 151 eyes operated with FS-LASIK and found that TCRP in a 4.0mm area can effectively predict changes after refractive surgery, consistent with our findings. However, Savini et al. [ 21 ] observed different results. Their research on PRK and LASIK surgery showed that annular TCRP with 3.0 mm and 2.0 mm annular TCRP can accurately reflect corneal refractive changes, whereas TCRP with a 4.0 mm annulus (equivalent to our TCRP4) is less accurate. This inconsistency may be due to the fact that the correlation between the refractive and corneal curvature changes is influenced by the ablation range and optical zone size, which differ across surgical methods. Although we believe that TCRP4mm is the most accurate index for evaluating corneal refractive changes, the conclusions of each study may not be applicable to all types of corneal refractive surgery and need to be carefully generalized to other surgical methods. This study had some limitations. We compared changes in corneal curvature and refractive error in the corneal plane after the operation; however, due to limited time, our data included only short-term follow-up cases (3 months after the operation). Because the short-term refractive state may be unstable, errors may have occurred. If postoperative refraction can be measured multiple times, the accuracy of the study can be improved. Another limitation is that the sample size was too small, and we only compared the data of the 3 mm to 5 mm annular area centered on the pupil, without analyzing the differences of other diameters or the annular area centered on the corneal apex; therefore, we could not conduct a comprehensive analysis and provide more reliable data support. In addition, we evaluated corneal refractive power only after surgery and did not verify these findings in eyes that had undergone SMILE surgery before cataract surgery. Therefore, more extensive research is required to verify and optimize these results. Conclusion Although Pentacam is the most accurate method for measuring TCRP4mm after corneal refractive surgery, it requires further verification and improvement before it can be widely used in combination with the existing intraocular lens calculation formula. Declarations Ethics approval and consent to participate The research protocol was approved by the Ethics Committee of the Second Hospital of Hebei Medical University, and the research was conducted in accordance with the Declaration of Helsinki. Given the prospective design of the research, written informed consent was obtained from all participants and approved by the Ethics Committee of the Second Hospital of Hebei Medical University. Human ethics and informed consent statement Applicable Competing interests The authors declare no competing interests. Funding This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors. Author Contribution Conceptualization: C. S., X.G.,B.Z.; Methodology: X.G.,B.Z.; Clinical studiesdemonstrate:C. S., S. S.; Data curation:C. S., S. S.; Formal analysis: X.G.,B.Z.,T.J.,C.T.; Writing-original draft preparation: S. S.; Writing-review and editing: C. S.; Supervision: X.G.,B.Z. Acknowledgement First and foremost, I would like to express my sincere gratitude to my supervisor, Professor Xiujin Guo, for her invaluable guidance, constant encouragement, and profound insights throughout the entire research process. From the initial conception of this study to the final revision of the manuscript, Professor Xiujin Guo has spared no effort to provide constructive suggestions, which have significantly shaped the quality of this paper. her rigorous academic attitude and dedication to scientific research have set a brilliant example for me.I am also deeply indebted to all the members of the Siyu Song.TaoJin.Bing Zhang.Chunmei Tong for their generous help and stimulating discussions during the experiments. Their selfless sharing of expertise and technical support has made the completion of this research possible.I wish to extend my heartfelt thanks to the participants who volunteered to take part in this study. Their cooperation and patience are the foundation of this research. I also thank the staff of Hospital for their help in recruiting participants and collecting clinical data.Last but not least, I would like to thank my family for their unconditional love, understanding, and support. Their constant care and encouragement have given me the strength to overcome difficulties and stay committed to my research. This paper is dedicated to them. Data Availability The datasets generated during the current study are available from the corresponding author upon reasonable request. References Ivarsen A, Asp S, Hjortdal J. Safety and complications of more than 1500 small-incision lenticule extraction procedures. Ophthalmology. 2014;121(4):822–8. Hansen RS, Lyhne N, Grauslund J, et al. Small-incision lenticule extraction (SMILE): outcomes of 722 eyes treated for myopia and myopic astigmatism. Graefes Arch Clin Exp Ophthalmol. 2016;254(2):399–405. Kamiya K, Shimizu K, Igarashi A, et al. Visual and refractive outcomes of femtosecond lenticule extraction and small-incision lenticule extraction for myopia. Am J Ophthalmol. 2014;157(1):128–34. Koch DD, Liu JF, Hyde LL, et al. Refractive complications of cataract surgery after radial keratotomy. Am J Ophthalmol. 1989;108(6):676–82. Lyle WA, Jin GJ. Intraocular lens power prediction in patients undergoing cataract surgery after radial keratotomy. Arch Ophthalmol. 1997;115(4):457–61. Seitz B, Langenbucher A, Nguyen NX, et al. Underestimation of intraocular lens power for cataract surgery after myopic photorefractive keratectomy. Ophthalmology. 1999;106(4):693–702. Gimbel H, Sun R, Kaye GB. Refractive errors in cataract surgery after previous refractive surgery. J Cataract Refract Surg. 2000;26(1):142–4. Lesher MP, Schumer DJ, Hunkeler JD, et al. Phacoemulsification with intraocular lens implantation after excimer photorefractive keratectomy: A case report. J Cataract Refract Surg. 1994;20:265–7. Kalski RS, Danjoux JP, Fraenkel GE, Rogers C, et al. Intraocular lens power calculation for cataract surgery after photorefractive keratectomy in patients with high myopia. J Refract Surg. 1997 Jul-Aug;13(4):362–6. Gimbel HV, Sun R. Accuracy and predictability of intraocular lens power calculation after laser in situ keratomileusis. J Cataract Refract Surg. 2001;27(4):571–6. Cua IY, Qazi MA, Lee SF. Intraocular lens calculations in patients with corneal scarring and irregular astigmatism. J Cataract Refract Surg. 2003;29(7):1352–7. Olsen T. Calculation of intraocular lens power: a review. Acta Ophthalmol Scand. 2007;85(5):472–85. Ho JD, Tsai CY, Tsai RJ, et al. Validity of the keratometric index: evaluation by the Pentacam rotating Scheimpflug camera. J Cataract Refract Surg. 2008;34(1):137–45. Savini G, Barboni P, Carbonelli M, et al. Agreement between Pentacam and videokeratography in corneal power assessment. J Refract Surg. 2009;25(6):534–8. Kopacz D, Maciejewicz P, Kecik D. Pentacam–nowe mozliwości obrazowania przedniego odcinka gałki ocznej [Pentacam–the new way for anterior eye segment imaging and mapping]. Klin Oczna. 2005;107(10–12):728 – 31.​. Chen D, Lam AK. Intrasession and intersession repeatability of the Pentacam system for posterior corneal assessment in normal human eyes. J Cataract Refract Surg. 2007;33(3):448–54. Bland JM, Altman DG. Statistical methods for assessing the agreement between two clinical measurement methods. Lancet. 1986;1(8476):307–10. Shammas HJ, Shammas MC, Garabet A, et al. Correcting corneal power measurements for intraocular lens power calculations after myopic laser in situ keratomileusis. Am J Ophthalmol. 2003;136(3):426–32. Kim JH, Lee Do, Joo CK. Measuring corneal power for intraocular lens power calculation after refractive surgery. Comparison of methods. J Cataract Refract Surg. 2002;28(11):1932. 8.​. Wang L, Booth MA, Koch DD. Comparison of intraocular lens power calculation methods in eyes that underwent LASIK. Ophthalmology. 2004;111(10):1825–31. Savini G, Hoffer KJ, Carbonelli M. Scheimpflug analysis of corneal power changes after myopic excimer laser surgery. J Cataract Refract Surg. 2013;39(4):605–10. Oh JH, Kim SH, Chuck RS. Evaluation of the Pentacam ray tracing method for measuring central corneal power after myopic photorefractive keratectomy. Cornea. 2014;33(3):261–5. Savini G, Calossi A, Camellin M, et al. Corneal ray-tracing versus simulated keratometry for estimating corneal power changes after excimer laser surgery. J Cataract Refract Surg. 2014;40(7):1109–15. Cao JX, Liu W, Liu Y, et al. Comparison of corneal refractive power measurements between Pentacam and IOL Master [J]. Int Eye Sci. 2019;19(1):113–7. Elbaz U, Barkana Y, Gerber Y, et al. Comparison of different techniques for measuring the anterior chamber depth and keratometry. Am J Ophthalmol. 2007;143(1):48–53. Pan H, Wang LH, Ma LX. Comparison of Pentacam and IOLMaster in measuring corneal curvature and anterior chamber depth. J Shandong Univ (Health Sciences). 2008;46:624–7. Li Lixin. Atlas of Ocular Ultrasound Diagnosis [Book]. Beijing: People's Medical Publishing House; 2003. pp. 22–3. Liu Houcang K, Ning. A study on the accuracy of Pentacam in measuring corneal refractive power after corneal refractive surgery [J]. J Clin Ophthalmol. 2016;24(6):538–41. Yanjun H, Jinhai H, Chao P, et al. Evaluation of total corneal power and prediction of intraocular lens power in patients after laser in situ keratomileusis [J]. Natl Med J China. 2012;92(33):2339–44. Borasio E, Stevens J, Smith GT. Estimation of true corneal power after keratorefractive surgery in eyes requiring cataract surgery: the BESSt formula. J Cataract Refract Surg. 2006;32(12):2004–14. Qian Y, Liu Y, Zhou X, et al. Comparison of Corneal Power and Astigmatism between Simulated Keratometry, True Net Power, and Total Corneal Refractive Power before and after. SMILE Lenticule Extr. 2017;2017:9659481. Savini G, Barboni P, Profazio V. Corneal power measurements using the Pentacam Scheimpflug camera after myopic excimer laser surgery. J Cataract Refract Surg. 2008;34(5):809–13. Mello GR, Roberts CJ, Smadja D, et al. Comparison of keratometric changes after myopic ablation: ray-tracing versus simulated keratometry. J Refract Surg. 2013;29(9):604–10. Wang L, Mahmoud AM, Anderson BL, et al. Total corneal power estimation: ray-tracing method versus Gaussian optics formula. Invest Ophthalmol Vis Sci. 2011;52(3):1716–22. Gyldenkerne A, Ivarsen A, Hjortdal JØ. Assessing corneal power changes after refractive surgery using Scheimpflug imaging. Ophthalmic Physiol Opt. 2015;35(3):299–307. Srivannaboon S, Reinstein DZ, Sutton HF, et al. Accuracy of Orbscan total optical power maps in detecting refractive change after myopic laser in situ keratomileusis. J Cataract Refract Surg. 1999;25(12):1596–9. Sónego-Krone S, López-Moreno G, Beaujon-Balbi OV. Direct method for measuring the power of the central cornea after myopic laser in situ keratomileusis. Arch Ophthalmol. 2004;122(2):159–66. Savini G, Barboni P, Carbonelli M, et al. Accuracy of corneal power measurements by a new Scheimpflug camera combined with Placido-disk corneal topography for intraocular lens power calculation in unoperated eyes. J Cataract Refract Surg. 2012;38(5):787–92. Hirayama M, Wang L, Koch DD, et al. Comparison of accuracy of intraocular lens calculations using automated keratometry, a Placido-based corneal topographer, and a combined Placido-based and dual Scheimpflug corneal topographer. Cornea. 2010;29(10):1136–8. Tables Table 1 to 5 are available in the Supplementary Files section. Additional Declarations No competing interests reported. Supplementary Files SCI121.docx Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. 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1","display":"","copyAsset":false,"role":"figure","size":734708,"visible":true,"origin":"","legend":"\u003cp\u003eTotal corneal refractive power obtained by different preoperative methods\u003c/p\u003e","description":"","filename":"floatimage1.png","url":"https://assets-eu.researchsquare.com/files/rs-8602154/v1/06a34cf777c833cae8d75390.png"},{"id":101019836,"identity":"49644297-c4f1-4311-a2d6-a72feb2c39b2","added_by":"auto","created_at":"2026-01-24 00:40:48","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":636057,"visible":true,"origin":"","legend":"\u003cp\u003eTotal corneal refractive power obtained by different methods 3 months after surgery\u003c/p\u003e","description":"","filename":"floatimage2.png","url":"https://assets-eu.researchsquare.com/files/rs-8602154/v1/2df2ea20adbe1a1f800926e6.png"},{"id":101019844,"identity":"9fada6b7-7a46-49d9-b39c-d481973338c8","added_by":"auto","created_at":"2026-01-24 00:40:48","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":734708,"visible":true,"origin":"","legend":"\u003cp\u003eTotal corneal refractive power obtained by different preoperative methods\u003c/p\u003e","description":"","filename":"floatimage1.png","url":"https://assets-eu.researchsquare.com/files/rs-8602154/v1/371af184a099f13aabd0e825.png"},{"id":101204380,"identity":"8b8ec7da-d36a-4dff-8116-183829b66567","added_by":"auto","created_at":"2026-01-27 09:42:49","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":636057,"visible":true,"origin":"","legend":"\u003cp\u003eTotal corneal refractive power obtained by different methods 3 months after surgery\u003c/p\u003e","description":"","filename":"floatimage2.png","url":"https://assets-eu.researchsquare.com/files/rs-8602154/v1/f5bc1c817ec98dba95baaff1.png"},{"id":102965716,"identity":"e8624ab6-bae8-4ba1-9632-8da37f27034e","added_by":"auto","created_at":"2026-02-19 04:32:35","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1117660,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-8602154/v1/9cb0aa3f-5df9-4e49-9fcc-1a56622a029b.pdf"},{"id":101019835,"identity":"7bf36d8f-7e30-43e7-bdf8-c47fa9a5f0af","added_by":"auto","created_at":"2026-01-24 00:40:48","extension":"docx","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":40072,"visible":true,"origin":"","legend":"","description":"","filename":"SCI121.docx","url":"https://assets-eu.researchsquare.com/files/rs-8602154/v1/dbf1855562f36c58ecded212.docx"}],"financialInterests":"No competing interests reported.","formattedTitle":"Analysis of Corneal Refractive Power Following SMILE Procedure","fulltext":[{"header":"Preface","content":"\u003cp\u003eCorneal refractive surgery has been common in China for more than 20 years. Technical progress has continually improved surgical methods. The field has advanced from early PRK to LASIK and then to personalized LASIK based on wavefront aberrations and corneal topography. Since 2011, the clinical use of SMILE has changed the landscape of traditional corneal-refractive surgery. SMILE differs from older methods that require corneal flaps. It was quickly adopted in China because of its advantages, such as reduced trauma and rapid corneal healing [\u003cspan additionalcitationids=\"CR2\" citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]. SMILE is currently the most advanced technology for this type of surgery. However, patients who undergo this surgery eventually develop age-related cataracts. Corneal refractive surgery has been widely performed in China for two decades. The technology in this field is constantly advancing and improving. The field has developed rapidly, from methods such as photorefractive keratectomy (PRK) to modern laser surgery. Post-refractive surgery cataract patients who undergo intraocular lens power calculations using standard corneal refractive measurements frequently end up with hyperopic outcomes following their procedure, as documented in multiple clinical studies [\u003cspan additionalcitationids=\"CR5 CR6 CR7 CR8\" citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e].As more people undergo this surgery, an accurate and reliable evaluation of corneal refractive power is needed. Before slit-scanning technology, doctors could not obtain data from the back of the cornea. They could only measure the anterior surfaces. Corneal refractive surgery has been widely performed in China for more than 20 years. Technical progress has improved surgical outcomes. The field has advanced rapidly from PRK to the current laser surgery. The calculation of the corneal diopter depends on a set relationship between the anterior and posterior cornea. Devices such as the standard corneal curvature meter, corneal topographic map system, and IOL Master aid in these measurements. The IOL Master is a common tool used in cataract surgery. It accurately measures the corneal diopter for normal corneas. However, measurement errors may occur if the corneal structure changes [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e, \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e, \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]. The IOL Master measures corneal diopters, similar to the traditional corneal curvature meter. It uses Gullstrand's model eye and the formula K = (n1)/r to quantify the mean curvature of the front surface. To determine the focusing capability of the cornea, we employed a theoretical relationship, presuming that the back curve measures 82% of the front one, while using a conventional light-bending constant of 1.3375 [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e].However, the cornea has both anterior and posterior surfaces that are not flat. Some question whether this assumption leads to accurate results [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eWith the new topographic measurement technology, doctors can examine both the anterior and posterior corneal surfaces. These tools simultaneously capture curvature data from both surfaces. There is no longer a need to assume a fixed relationship between the two surfaces to calculate the corneal refractive power. Examples of these devices include Pentacam, Sirius, Galilei, and Orbscan.Pentacam is an advanced 3D diagnostic tool, which is specially used to examine the front of the eye [\u003cspan additionalcitationids=\"CR15 CR16\" citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e]. It adopts Scheimpflug imaging technology and collects data by rotation. Pentacam is famous for its high accuracy and rich information, which can comprehensively evaluate the eye structure. It can calculate the shape of the anterior and posterior corneal layers, the overall corneal thickness and optical characteristics. This equipment provides about 40 different indexes, which are used to analyze the focusing ability of cornea and realize in-depth examination. In order to draw the optical power of cornea, Pentacam uses many methods, including SimK based on projection readings, TNP calculated by Gaussian lens theory, TCRP determined by ray modeling, and EKR providing standardized corneal curvature readings. These assessment techniques examine different ranges from 1 mm to 8 mm through overall and segmented analysis. The measurement can be aligned based on the pupil center point or the corneal vertex. Many previous studies have compared SimK, TNP, TCRP, and EKR in various corneal refractive surgeries, including LASIK, LASEK, and PRK. Research has generally shown that TCRP can most accurately reflect corneal refractive power after surgery. Corneal features may differ between ethnic groups; however, few studies have evaluated these methods before and after SMILE in Chinese patients. Therefore, careful selection and analysis of SMILE patient data in China is very important. This will help us identify the most effective and accurate method for measuring corneal refractive power in Chinese patients. In this study, we used SimK, TNP, TCRP, EKR, and K-means to measure the corneal refractive power before and after SMILE. The methods were evaluated to determine the optimal accuracy for patients with cataracts after post-refractive corneal surgery.\u003c/p\u003e"},{"header":"Materials and Methods","content":"\n\u003ch3\u003e1. Research subjects\u003c/h3\u003e\n\u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003e1.1 Inclusion criteria\u003c/h2\u003e \u003cp\u003eTo participate in this study, you must be at least 18 years old. Prescription stability for glasses or contact lenses is required over the prior 24-month period.The degree of myopia should be between \u0026minus;\u0026thinsp;1.00 and \u0026minus;\u0026thinsp;8.00. Your corrected vision with glasses or contact lenses must be 20/25 or better. If you wear soft contact lenses, stop using them at least 14 days before the appointment. For hard contact lenses, stop using them for a full month. Your intraocular pressure should be between 10 and 21 mmHg. You should not have eye conditions such as early keratoconus or severe corneal scarring. You should not have health problems such as diabetes, keloids, depression, or connective tissue diseases.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003e1.2 Inclusiostatus As\u003c/h2\u003e \u003cp\u003eFrom September 2020 to January 2021, 37 people (70 eyes in total, 37 right eyes and 33 left eyes) underwent SMILE surgery at our myopia laser treatment center. All patients were re-examined three months after the operation. This group comprised 20 men and 17 women, with an average age of 26.3\u0026thinsp;\u0026plusmn;\u0026thinsp;5.2 years (range: 18\u0026ndash;40 years). Before the operation, their average spherical equivalent diopter was (-4.58\u0026thinsp;\u0026plusmn;\u0026thinsp;1.36)D, ranging from \u0026minus;\u0026thinsp;7.2 D to -1.75 D. After the operation, the spherical lens diopter ranged from \u0026minus;\u0026thinsp;1.50 D to -0.75 D, with an average of (-0.10, 0.44) D.\u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003e2. Research methods\u003c/h3\u003e\n\u003cdiv id=\"Sec7\" class=\"Section2\"\u003e \u003ch2\u003e2.1 Preoperative and postoperative examinations\u003c/h2\u003e \u003cdiv id=\"Sec8\" class=\"Section3\"\u003e \u003ch2\u003e2.1.1 Basic examination\u003c/h2\u003e \u003cp\u003e1) Visual acuity: Before and after the operation, we used a standard eye chart to check the vision of each patient without glasses and their best vision after wearing them.\u003c/p\u003e \u003cp\u003e2) Optometry: We performed subjective and objective optometry examinations before and after the operation. These included testing with natural and dilated pupils.\u003c/p\u003e \u003cp\u003e3)Intraocular pressure (IOP): The intraocular pressure was measured three times using a non-contact intraocular pressure meter, and a final average result was calculated.\u003c/p\u003e \u003cp\u003e4) Slit lamp: A slit lamp microscope was used to examine the corneal condition before and after surgery.\u003c/p\u003e \u003cp\u003e5) Fundus: The fundus was examined using a direct ophthalmoscope and three-mirror contact lens to exclude fundus diseases. If necessary, fundus laser treatment was performed.\u003c/p\u003e \u003cp\u003e6) 6) Corneal thickness: To anesthetize the eye surface, we applied a drop of 0.4% proparacaine hydrochloride to the lower eyelid conjunctival sac. Using the Pachmate ultrasonic thickness gauge, we took five consecutive measurements at the coneal center and recorded the lowest reading each time.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec9\" class=\"Section3\"\u003e \u003ch2\u003e2.1.2 Examination with Pentacam HR Three-dimensional Anterior Segment Analyzer\u003c/h2\u003e \u003cp\u003eThe German-manufactured Pentacam HR employs the Scheimpflug principle as a 3D analyzer of the anterior segment.By rotating the crack beam, it can take 50 crack images at different angles from 0 to 180 degrees in 2 seconds.This method will collect data from a total of 138,000 points on the anterior and posterior surfaces of the cornea. The final result is a complete topographic map evaluation of the anterior and posterior parts of the cornea, including detailed schematic diagrams of tangential curvature and axial curvature. These images can highlight important corneal features, such as eccentric position, central radius of curvature and astigmatism. This method improves the accuracy of reading in the central area, and can also determine the curvature data of selected points on the anterior and posterior surfaces of the cornea. Operating steps: In a dark environment, ask the patient to put his chin and forehead in a fixed position on the designated bracket. Instruct the patient to stare at a static red dot. When it is clearly focused, the system will automatically start scanning the eyes. The scanning should be repeated three times in total, and only the scanning results that meet the image quality standards will be adopted. All measurements are carried out by professional technicians.The data collected by Pentacam HR included corneal central readings with diameters of 3, 4, and 5 mm, centered on the pupil, including SimK, TNP, TCRP, and 4.5 mm EKR.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec10\" class=\"Section3\"\u003e \u003ch2\u003e2.1.3 Examination by IOL Master\u003c/h2\u003e \u003cp\u003eThe working principle of IOLMaster uses corneal reflection to measure the size of the image reflected by six light spots projected from the front surface of the cornea, evenly distributed on a circle with a diameter of 2.3 mm. The distance between the reflected light points must be calculated. According to Gullstrand's model eye formula k=(n-1)/r, this instrument can only measure the average curvature of the anterior surface of the cornea. Assuming that the ratio of the curvature radius of the posterior surface to that of the anterior surface of the cornea is 82% and the standard refractive index is 1.3375, the refractive power of the cornea can be calculated. The measurement steps were as follows: the patient was instructed to lean his chin and forehead against the designated bracket while staring at a target point on the equipment. IOL Master will measure K1 and K2, respectively, and the final value (Km) is the average of three consecutive measurements; the calculation formula is Km = (K1\u0026thinsp;+\u0026thinsp;K2)/2. The data collected by the IOL Master were Km.\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv id=\"Sec11\" class=\"Section2\"\u003e \u003ch2\u003e2.2 Surgical methods\u003c/h2\u003e \u003cp\u003eAll steps were completed by the same experienced surgeon. We instructed the patient to use gatifloxacin eye drops four times a day for three days before the operation to prevent infection. The same regimen was continued postoperatively. Before the operation, a drop of 0.4% proparacaine hydrochloride eye drops was instilled into the conjunctival sac for local anesthesia. The conjunctival sac was then washed with warm saline, and the skin around the eyes was disinfected with a cotton swab dipped in 0.5% povidone-iodine. Disinfection is centered on blepharoptosis, from the inside out, ranging from the hairline to the line connecting the nasolabial groove and the earlobe, crossing the nasal midline inward. The disinfection process was repeated three times. After standard disinfection, a corneal flap and matrix lens were created using the VisuMax femtosecond laser system (Carl Zeiss, Germany). The laser parameters were set as follows: pulse energy is 140nJ, pulse frequency is 500kHz, corneal flap thickness is 120um, flap diameter, 7 mm; lens diameter is 6-6.5 mm, substrate thickness increased by 10-15um, lateral incision, 2 mm; and angle of lens and small incision, 90 \u0026deg;. The patient lies on his back on the operating table, with his head straightened to ensure that his forehead and jaw are at the same level and that the line from the jaw to the bridge of the nose is centered on the midline. After administering topical anesthesia, the patient was asked to gaze directly at the light above. The position of the corneal reflection point relative to the pupil center was recorded and remembered. Before making the lens, the green fixation light was adjusted to the reflection point. The device was then slowly allowed to contact the cornea until 80% contact was achieved, and negative-pressure suction was initiated. The front and back surfaces of the lens were scanned at the incision site using a femtosecond laser. The lens was gently and quickly separated and removed through a small incision after complete separation. Check whether the lens is complete. Finally, the corneal flap bed was washed with a balanced salt solution, and the excess liquid was removed with a sterile sponge to complete the operation.\u003c/p\u003e \u003cp\u003e \u003cb\u003e2.3Assessment of Variations in Corneal Refractive Power Following Small Incision Lenticule Extraction (SMILE) Procedure: A Comparative Analysis of Preoperative and Three-Month Postoperative Measurement Outcomes\u003c/b\u003e \u003c/p\u003e \u003cdiv id=\"Sec12\" class=\"Section3\"\u003e \u003ch2\u003e2.3.1 Refractive changes in the corneal plane (△SE)\u003c/h2\u003e \u003cp\u003eTo calculate the correction, we converted the degree of the glasses plane to the degree of the cornea plane, assuming that the lens was 12 mm from the cornea during the test. The difference in the corneal plane degree before and after the operation is the refractive change brought about by the SMILE operation, that is, the amount of corneal plane refractive state change after the operation.\u003c/p\u003e \u003cp\u003eSpherical equivalent (SE)\u0026thinsp;=\u0026thinsp;spherical diopter\u0026thinsp;+\u0026thinsp;0.5 \u0026times; cylindrical diopter\u003c/p\u003e \u003cp\u003eFor the conversion of preoperative and postoperative spectacle-plane equivalent spherical power (SE) to corneal-plane equivalent spherical power (MR), the formula MR\u0026thinsp;=\u0026thinsp;SE / (1\u0026ndash;0.012 \u0026times; SE) was used.\u003c/p\u003e \u003cp\u003eSurgical corneal refractive power shift (ΔSE): ΔSE\u0026thinsp;=\u0026thinsp;preoperative MR - postoperative MR\u003c/p\u003e \u003cp\u003e \u003cb\u003e2.3.2 The corneal refractive power Km was obtained using the IOL Master, and the simulated corneal refractive power ( SimK) was obtained using Pentacam.\u003c/b\u003e \u003c/p\u003e \u003cp\u003eSimilar to the traditional keratometer, Km in the IOL Master and SimK in Pentacam are based on Gullstrand's schematic eye. These devices regard the cornea as a thin lens and can only measure the average curvature of the front surface. They assumed that the ratio of the posterior to anterior radius of curvature was fixed at 82% and then calculated the corneal refractive power using a standard refractive index of 1.3375.\u003c/p\u003e \u003cp\u003eK = (n \u0026minus;\u0026thinsp;1)/R(1)\u003c/p\u003e \u003cp\u003eHere, n\u0026thinsp;=\u0026thinsp;1.3375, and the refractive index of air is 1.00. R represents the radius of curvature of a specific area on the anterior surface of the central cornea (in meters). The difference lies in the measurement method: the IOL Master calculates corneal refractive power (Km) by taking six points on a circle with a diameter of 2.3 mm. In contrast, Pentacam was used in this study to determine the corneal refractive power (Simk) from measurements at 3, 4, and 5 mm from the center of the cornea.\u003c/p\u003e \u003cp\u003eThe basic principle of TNP in Pentacam is to imagine the cornea as a thick lens. This method uses the \u0026ldquo;paraxial approximation\u0026rdquo; calculation method and assumes that light propagates to the posterior surface of the cornea in parallel. By assuming that light passes through the front and back surfaces of the cornea in parallel, they used the Gaussian optical formula (which is specifically used to calculate thick lenses) to calculate the total refractive power of the entire cornea.\u003c/p\u003e \u003cp\u003eK=(n1-n)/r1+(n2-n1)/r2 (2)​\u003c/p\u003e \u003cp\u003eIn this context, air possesses a refractive index of n0\u0026thinsp;=\u0026thinsp;1, whereas the actual refractive indices of the cornea and aqueous humor are n1\u0026thinsp;=\u0026thinsp;1.376 and n2\u0026thinsp;=\u0026thinsp;1.336, respectively. The curvature radii for the anterior and posterior corneal surfaces are denoted by r1 and r2, respectively, with the reference plane established at the second principal plane anterior to the cornea.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec13\" class=\"Section3\"\u003e \u003ch2\u003e2.3.3 Total corneal power (TCRP) based on the tracy-tracing method\u003c/h2\u003e \u003cp\u003eThe TCRP principle in Pentacam uses ray tracing, which tracks the path of a parallel incident light beam through the anterior and posterior surfaces of the cornea, according to Snell's law. The focusing distance was measured and converted to corneal diopters.\u003c/p\u003e \u003cp\u003eK\u0026thinsp;=\u0026thinsp;n/f (3)\u003c/p\u003e \u003cp\u003eIn this case, n was equal to 1.336, f represented the focal length, and the reference plane was the anterior surface of the cornea.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec14\" class=\"Section3\"\u003e \u003ch2\u003e2.3.4 Equivalent keratometry reading (EKR)\u003c/h2\u003e \u003cp\u003eIn 2006, Oculus and Holladay jointly launched the Pentacam Holladay report, which was specifically used to evaluate the corneal refractive power of patients with cataracts who had undergone corneal refractive surgery. This adjustment can make the K value measured by Pentacam compatible with the traditional intraocular lens power calculation formula. The specific algorithm is as follows.\u003c/p\u003e \u003cp\u003eEKR(D)=(n1-1)Ra+(n-1)(1\u0026ndash;1/R2)\u0026times;R1/Rp ༈4༉\u003c/p\u003e \u003cp\u003eIt can be simplified as: EKR\u0026thinsp;=\u0026thinsp;0.376/Ra \u0026minus;\u0026thinsp;0.03165/Rp。 (5)\u003c/p\u003e \u003cp\u003eThe refractive index of the cornea is n1\u0026thinsp;=\u0026thinsp;1.376, which differs from the standard value of n\u0026thinsp;=\u0026thinsp;1.3375. Meanwhile, Ra denotes the curvature radius of the front corneal surface, and Rp denotes that of the rear surface. For our investigation, we focused on a 4.5 mm central zone of the cornea, known as the EKR.\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv id=\"Sec15\" class=\"Section2\"\u003e \u003ch2\u003e2.4 Statistical analysis\u003c/h2\u003e \u003cp\u003eStatistical analysis was conducted using SPSS version 22.0, with continuous variables presented as means\u0026thinsp;\u0026plusmn;\u0026thinsp;standard deviations. To assess the normality of distribution for all continuous variables, we employed the Kolmogorov-Smirnov test.Because the p-value is greater than 0.05, the data are normal and can be tested using parametric tests. We used repeated-measures ANOVA to compare differences in Km, EKR4.5 mm, Simks, TNPs, and TCRPs before and after the operation, and then used the Bonferroni method for post hoc comparisons. In GraphPad Prism, the same letter in a column indicates no difference, and different letters indicate a difference in significance. A paired T-test was used to compare the changes in diopter (△ SE) and corneal curvature (△ K) before and after the operation. Statistical significance was set at p\u0026thinsp;\u0026lt;\u0026thinsp;0.05.The consistency of ΔSE and ΔK was analyzed using the Bland-Altman method, and the deviation was expressed as 95% limits of agreement (LoA). The Pearson correlation analysis revealed a significant association between the two datasets, with a p-value less than 0.05.\u003c/p\u003e \u003c/div\u003e"},{"header":"Results","content":"\u003cp\u003e\u003cstrong\u003e1. General results\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThestudyanalyzed70eyesfrom37patents(37right、33left)comprising20menand17womer、withationage from 26.35. 2years(range,18-40).The spherical equivalent (SE) values at the corneal plane were -5.04\u0026plusmn;1.33 D and 0.12\u0026plusmn;0.31 D, respectively. The change in refractive status (△SE) at the corneal plane before and after surgery was 4.92\u0026plusmn;1.14 D.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e2. Differences in corneal refractive power obtained by different methods before surgery\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003ePreoperatively, the values of EKR4.5mm, Simk 3 \u0026amp; 4 \u0026amp; 5 mm, TNP 3 \u0026amp; 4 \u0026amp; 5 mm, TCRP 3 \u0026amp; 4 \u0026amp; 5 mm measured by Pentacam and Km measured by IOL Master were 43.21\u0026plusmn;0.64D, 43.52\u0026plusmn;0.64D, 43.46\u0026plusmn;0.64D, 43.43\u0026plusmn;0.65D, 42.25\u0026plusmn;0.67D, 42.15\u0026plusmn;0.66D, 42.05\u0026plusmn;0.67D, 42.89\u0026plusmn;0.67D, 42.93\u0026plusmn;0.66D, 43.06\u0026plusmn;0.67D and 43.68\u0026plusmn;0.63D, respectively. Through the statistical analysis of pairwise comparison, it was found that there were obvious differences in corneal refractive power measured by different preoperative methods (ANOVA: P\u0026lt;0.05). Specifically, the measured values of Km and Simks are the highest, EKR4.5 mm and TCRPs are in the middle, and TNPs is the lowest (P \u0026lt; 0.05). The analysis further shows that there are considerable differences between Km, EKR4.5 mm and Simks, TNPs and TCRPs, and all these pairs show obvious differences (P \u0026lt; 0.05). On the contrary, no significant difference was found among other preoperative refractive indexes used for cornea (P \u0026gt; 0.05). The measured values from 3 mm, 4 mm and 5 mm regions also showed no statistically significant difference (P \u0026gt; 0.05) (Table 1 and Figure 1).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e3.\u0026nbsp;\u003c/strong\u003e\u003cstrong\u003eDifferences in corneal refractive power obtained by different methods at 3 months after surgery\u003c/strong\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThree months after the surgical intervention, a series of parameters related to corneal refractive power were evaluated using two different clinical measurement instruments, namely the Pentacam and IOL Master systems. Specifically, parameters such as EKR4.5mm, △Simk (3, 4, 5 mm), △TNP (3, 4, 5 mm), △TCRP (3, 4, 5 mm), were quantified via the Pentacam system, while the Km parameter was determined through the IOL Master device. The measured values of these parameters were recorded as follows: EKR4.5mm was 38.52 \u0026plusmn; 1.16 diopters (D), Simk3mm was 39.41 \u0026plusmn; 0.92D, Simk4mm was 39.39 \u0026plusmn; 0.93D, Simk5mm was 39.40 \u0026plusmn; 0.90D, TNP3mm was 37.66 \u0026plusmn; 1.07D, TNP4mm was 37.59 \u0026plusmn; 1.04D, TNP5mm was 37.60 \u0026plusmn; 1.01D, TCRP3mm was 37.71 \u0026plusmn; 1.07D, TCRP4mm was 37.93 \u0026plusmn; 1.09D, TCRP5mm was 38.32 \u0026plusmn; 1.07D, and the Km value was 39.51 \u0026plusmn; 1.03D respectively. Subsequent pairwise comparison analysis was conducted to examine the differences in corneal refractive power values derived from the distinct measurement methods at three months postoperatively. The analysis of variance (ANOVA) results indicated statistically significant disparities in corneal refractive power measurements obtained using various methodologies (ANOVA: P \u0026lt; 0.05). Among the measured parameters, Km had the largest value. This was followed, in descending order, by the Simk series of parameters, the EKR4.5 mm parameter, and the TCRP series of parameters, whereas the TNP series of parameters had the smallest values; all differences were statistically significant (P \u0026lt; 0.05). A systematic comparison among individual parameter groups yielded the following finding: No significant disparity was noted between the Km value and the SimK parameter group, with a p-value greater than 0.05. However, notable differences were observed between Km and other preoperative corneal metrics, with a P-value below 0.05. Similarly, the EKR4.5 mm parameter showed no statistical variation in the TCRP group (P \u0026gt; 0.05), but distinct differences were noted when compared with other preoperative refractive power measurements (P \u0026lt; 0.05). The same trend was observed in the comparison between the SimK parameters and other preoperative refractive power metrics, with no significant variance (P \u0026gt; 0.05) but significant differences with other parameters (P \u0026lt; 0.05). The TNP and TCRP parameters were also found to be statistically indistinguishable from each other (P \u0026gt; 0.05), while they exhibited significant differences from other preoperative measurements (P \u0026lt; 0.05). Finally, the TCRP parameters were not statistically different from those of the EKR4.5 mm and TNP groups (P \u0026gt; 0.05), but they did show significant differences with other corneal measurements (P \u0026lt; 0.05). The analysis also confirmed that the measurements at 3-, 4-, and 5-mm regions were not significantly different from one another (P \u0026gt; 0.05).( Table 2 and Figure 2).\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e4. Variations in the relationship between changes in corneal curvature (△K) and shifts in refractive power at the corneal plane (△SE) before and after surgical intervention\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThree months after the surgical procedure, the corneal curvature (K) value showed a notable reduction from the preoperative baseline, with a statistically significant difference (P \u0026lt; 0.05). The changes in corneal refractive power before and after surgery, including △EKR4.5mm, △Simk/TNP/TCRP 3/4/5mm, and △Km, were 4.69 \u0026plusmn; 1.13D, 4.11 \u0026plusmn; 1.00D, 4.07 \u0026plusmn; 0.97D, 4.03 \u0026plusmn; 0.90D, 4.59 \u0026plusmn; 1.17D, 4.56 \u0026plusmn; 1.12D, 4.45 \u0026plusmn; 1.05D, 5.18 \u0026plusmn; 1.14D, 5.01 \u0026plusmn; 1.10D, 4.75 \u0026plusmn; 1.12D, and 4.17 \u0026plusmn; 1.06D, respectively. The differences between these values and △SE were -0.23 \u0026plusmn; 0.42D, -0.81 \u0026plusmn; 0.49D, -0.85 \u0026plusmn; 0.45D, -0.89 \u0026plusmn; 0.30D, -0.33 \u0026plusmn; 0.37D, -0.36 \u0026plusmn; 0.48D, -0.47 \u0026plusmn; 0.24D, 0.26 \u0026plusmn; 0.39D, 0.09 \u0026plusmn; 0.21D, -0.18 \u0026plusmn; 0.15D, and -0.75 \u0026plusmn; 0.36D, respectively. When analyzing the correlation between changes in corneal curvature (△k) derived from various measurement techniques before and after surgery and the corresponding changes in spherical equivalent refraction (△SE), our findings indicated that the discrepancy between △TCRP4mm and △SE was the only one that did not reach statistical significance.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e5. Correlation analysis of changes in corneal curvature (△K) and refractive power variations at the corneal plane (△SE) preoperatively and postoperatively\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThere were positive correlations between \u0026Delta;EKR 4.5, \u0026Delta;Simk 3/4/5, \u0026Delta;TNP 3/4/5, \u0026Delta;TCRP 3/4/5, \u0026Delta;Km with △SE (r = 0.933, 0.982, 0.978, 0.981, 0.948, 0.975, 0.947, 0.985, 0.989, 0.983, 0.950, all P \u0026lt; 0.01). The highest correlations were observed between △TCRP 3 mm, △TCRP 4 mm, △TCRP 5 mm, and △SE (r = 0.985, r = 0.989, and r = 0.983, respectively) ( Table 4).\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e6. Analysis of the Consistency between the Alteration in Corneal Curvature (△K) and the Variation in Refractive Power at the Corneal Plane (△SE) Pre - and Post - surgery\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eIn addition, we computed and determined the 95% limits of agreement for a series of different parameters, including △EKR 4.5 mm, △Simk 3-5 mm, △TNP 3-5 mm, △TCRP 3-5 mm, △Km, and △SE. Specifically, the 95% agreement range for △EKR 4.5mm was from -1.05 to 0.59 diopters (D); for △Simk 3mm, it was within -1.77 to 0.15 D; for △Simk 4mm, it spanned from -1.73 to 0.33 D; for △Simk 5mm, it was between -1.48 and 0.30 D; for △TNP 3mm, it ranged from -1.06 to 0.40 D; for △TNP 4mm, it covered -1.30 to 0.58 D; for △TNP 5mm, it was in the interval of -0.94 to 0.00 D; for △TCRP 3mm, it was between -0.50 and 1.02 D; for △TCRP 4mm, it fell within the range of -0.32 to 0.50 D; for △TCRP 5mm, it was within -0.47 to 0.11 D; and for △Km, it spanned from -1.46 to 0.04 D. Among these difference parameters, △TCRP 5 mm, △TCRP 4 mm, and △SE exhibited particularly high consistency, with their respective 95% limits of agreement being -0.47 to 0.11 D and -0.32 to 0.50 D.( Table 5). \u0026nbsp;\u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003eCorneal refractive surgery alters the corneal and anterior segment structures, leading to changes in some parameters that affect the accuracy of existing methods for calculating intraocular lens (IOL) power. Among these factors, the main source of error is the calculation of the corneal diopter [\u003cspan additionalcitationids=\"CR19\" citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e]. Although many techniques are available for accurately measuring corneal diopter after surgery, most rely on indirect estimates based on assumptions and usually require preoperative data. To date, there is no widely accepted method for directly and accurately measuring the corneal diopter after refractive surgery. The ideal solution is to find a technology that can directly measure the true corneal diopter without relying on assumptions or preoperative data and is also compatible with IOL calculation formulas. In recent years, the IOL Master and Pentacam have been widely studied and used in clinics as non-contact examination equipment. Because of their different measurement principles, it is crucial to evaluate the accuracy of their results in the clinic. Based on the principle of corneal curvature measurement, the IOL Master can only measure the average curvature of the anterior corneal surface, with limited sampling points, and is unable to evaluate the central corneal area. Pentacam uses the rotating slit optical scanning method based on Scheimpflug imaging technology, which can generate different corneal curvature measurement data from multiple angles. Regardless of corneal refractive index variations, this technique delivers precise measurements of corneal refractive power, maintaining accuracy even when the anterior and posterior corneal surface curvature ratios are altered or when post-surgical refractive index values become questionable [\u003cspan additionalcitationids=\"CR22\" citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e].In this study, the corneal curvature measured by the IOL Master before and after refractive surgery was compared with that measured using different Pentacam methods. The results showed no statistically significant difference between the IOLMaster Km and SimK values of Pentacam before the operation. This is consistent with the results of Cao et al. [\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e], who also found no significant difference between the measured values from SimK and IOL Master at a 3 mm center on Pentacam. However, Elbaz et al. [\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e] studied 22 normal eyes (with an average age of 56.3 years) and reported a significant difference between the 3 mm SimK in the center of the Pentacam and the IOL Master Km. Similarly, Pan et al. [\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e, \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e] compared the left eyes of 169 college students and found a significant difference between the SimK values of Pentacam and Km values of IOL Master, which is in contrast to our findings. Our findings differ from those of Elbaz et al. and Pan Hong et al., which may be due to differences in age, eyes, myopia, hyperopia, and the number of participants. However, most previous studies focused on normal eyes without corneal refractive surgery, and few have reported comparisons of corneal curvature after surgery using Pentacam and IOL Master. Therefore, this study aims to address this problem. Our results show that there is no obvious mathematical difference between the SimK values measured by Pentacam and the Km values measured by IOL Master after corneal refractive surgery. However, compared with the values of EKR4.5 mm, TNPs, and TCRPs, the differences were large, with average differences of 1.04D, 1.9D, and 1.60D, respectively. We should recognize that if there is a 1D error in measuring the corneal curvature, there will also be a 1D error in calculating intraocular lens power, which is unacceptable in clinical practice [\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e]. Therefore, although there is no obvious mathematical difference between the simulated corneal curvature measured by Pentacam and IOL Master after surgery, the difference is more than 1D compared with other K-value measurement methods, which means that the K-values of these two machines cannot be used casually for eyes that have undergone corneal refractive surgery.\u003c/p\u003e \u003cp\u003eIn the Holiday report, EKR was calculated by further optimizing the Gaussian optical formula, this time using the equivalent refractive power of the cornea in the 4.5 mm area, known as the 4.5 mm EKR. Some studies have compared EKR values with TNP and Simkacrossn in different diameter ranges, as well as with other commonly used clinical methods, such as the clinical history and Shammas methods, and have presented different views. However, to the best of our knowledge, no study has explored the relationship between EKR measurements and TCRP after refractive surgery. Our research includes a 4.5 mm EKR and compares it with the K values obtained using the other four methods. The findings indicated that at the three-month mark, there was no appreciable discrepancy between the 4. mm EKR and TCRPs; however, a substantial difference was noted when compared to other pre-operative corneal measurements. Liu Houcang et al. [\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e] obtained the K values for SimK, 4. mmTNP, 5.0 mmTNP, 4.5 mmEKR, the clinical history method, Shammas method, and the Haigis-L method by analyzing data from 121 eyes three months after LASIK/SMILE. They found significant statistical differences between 4.5 mm EKR and SimK and between 4.0 mm TNP and 5.0 mm TNPe, consistent with our findings. The equivalent refractive power was obtained by a secondary adjustment based on the Gaussian optical formula, which accounts for the accurate refractive index of the corneal tissue, corneal thickness, and the influence of the posterior surface. The simulated corneal refractive power only considers the front surface of the cornea and a standard refractive index of 1.3375; however, this is not the actual refractive index. Therefore, a difference exists between the equivalent corneal refractive power and the simulated refractive power after surgery. After corneal refractive surgery, there was no significant statistical difference between EKR4.5 mm and TCRPs, which may be because the corneal surface is not a perfect sphere but an aspheric surface with a steeper center and flatter periphery with spherical aberration. Because the equivalent refractive power and ray-tracing method consider spherical aberration based on the real refractive index, in theory, EKR4.5 mm should be able to reliably estimate the corneal refractive power after surgery. However, there was a significant difference between △EKR4.5 mm and △SE, and the 95% consistency limit was very wide, which indicates that the EKR value of 4.5 mm is not a good index to reflect the changes in corneal refractive power before and after surgery in this study.\u003c/p\u003e \u003cp\u003eIn this study, we used five methods (SIMK, TNP, TCRP, EKR, and) KMto evaluate the measurement results of corneal refractive power before and after the SMILE operation and compared them with the change in corneal planar refractive power (ΔSE). We found that these five methods yielded different results in evaluating corneal refractive power, among which ΔTCRP4mm was closest to ΔSE, with high consistency and correlation. Many scholars at home and abroad have also used SimK, TNP, and TCRP to evaluate corneal refractive power. Recent research indicates considerable disparities among simulated corneal refractive power (SimK), true net refractive power (TNP) derived from the Gaussian thick lens formula, and corneal refractive power (TCRP) gleaned through ray-tracing techniques in both unoperated and surgically altered eyes. Simulating corneal refractive power often overestimates it after surgery [\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e, \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e, \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e, \u003cspan additionalcitationids=\"CR31 CR32 CR33 CR34\" citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e], whereas corneal curvature (TCRP) calculated by ray tracing accurately reflects the refractive changes caused by the excimer laser [\u003cspan additionalcitationids=\"CR35 CR36\" citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e], consistent with our findings. Our study found that the value measured by TCRP before the operation was approximately 0.5 D lower than that measured by SimK. Current studies have shown that Simk and TCRP values differ in both normal eyes and eyes that have undergone refractive surgery, with Simk being consistently higher. Savini et al. [\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e] said that the TCRP measured by Sirius in normal eyes was 0.6 D, lower than that of Simk. Hirayama et al. [\u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e] also found that Simk was 0.4 D higher than TCRP when measured with Galilei. Three months after the operation, the TCRP was approximately 1.4 D lower than SimK, which was similar to the result reported by Huo et al.. [\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e]. They found that the TCRP was 1.75 D lower than Simk in eyes undergoing refractive surgery. The main difference between these two methods arises from two key aspects. First, they used different refractive indices. Simk was calculated according to Gullstrand's standard eye model, using a standard refractive index of 1.3375. This model assumes that the anterior-to-posterior corneal curvature ratio is fixed at 82% and that the corneal thickness is 500 microns. Once the fixed relationship between these curvatures is altered, this method becomes imprecise. In contrast, the TCRP uses ray tracing, which applies Snell's law to trace the paths of parallel rays passing through the anterior and posterior surfaces of the cornea. It first measures the focal length, then converts the focal length into corneal refractive power, and uses the actual refractive index (air: 1, cornea: 1.376, aqueous humor: 1.336), thus avoiding reliance on a hypothetical corneal refractive index when calculating curvature. Second, the reference planes differ. Simk calculation regards the cornea as a thin lens and defines its refractive power at the posterior vertex of the cornea. In contrast, takes the anterior surface of the cornea as the reference plane, and both the anterior and posterior surfaces of the cornea are considered in the comprehensive analysis.\u003c/p\u003e \u003cp\u003eOur study found that TNP's performance in evaluating corneal refractive surgery was suboptimal, consistent with previous research [\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e, \u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e, \u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e, \u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e]. In addition, TCRP was higher than TNP before and 3 months after surgery. Qian et al. [\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e] studied the data on SimK, TNP, and TCRP from 144 patients who underwent SMILE, and found that TCRP was higher than TNP before and 6 months after the operation. The difference between the TCRP and TNP is that they use different refractive reference surfaces. The TCRP references the anterior surface of the cornea, whereas the TNP uses the second principal plane anterior to the cornea. In addition, Gaussian optics operates as a streamlined framework that employs the paraxial approximation while mistakenly treating rays as parallel at the rear surface\u0026mdash;a flawed premise given that these beams have already undergone refraction at the front surface and anything but remain parallel to it. Moreover, this discrepancy becomes particularly pronounced following myopia-corrective procedures, where alterations in corneal thickness coupled with the modified ratio of anterior to posterior curvature radii impact Gaussian optics to a far greater extent than they do ray-tracing methodologies [\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e].Notably, our research found that the TCRP performance in the 4 mm area was better than that in other measurement ranges. This result is consistent with the principle of the average value of the central 4 mm area used by Galilei in the default calculation formula for intraocular lens power. Similarly, Qian et al. [\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e] reported similar results. They found that the annular TCRP values of 3 mm and 4 mm were closer to ΔSE than to ΔSimK, ΔTNP, and ΔTCRP six months after the SMILE operation. Gyldenkerne et al. [\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e] studied 410 eyes operated with SMILE and 151 eyes operated with FS-LASIK and found that TCRP in a 4.0mm area can effectively predict changes after refractive surgery, consistent with our findings. However, Savini et al. [\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e] observed different results. Their research on PRK and LASIK surgery showed that annular TCRP with 3.0 mm and 2.0 mm annular TCRP can accurately reflect corneal refractive changes, whereas TCRP with a 4.0 mm annulus (equivalent to our TCRP4) is less accurate. This inconsistency may be due to the fact that the correlation between the refractive and corneal curvature changes is influenced by the ablation range and optical zone size, which differ across surgical methods. Although we believe that TCRP4mm is the most accurate index for evaluating corneal refractive changes, the conclusions of each study may not be applicable to all types of corneal refractive surgery and need to be carefully generalized to other surgical methods.\u003c/p\u003e \u003cp\u003eThis study had some limitations. We compared changes in corneal curvature and refractive error in the corneal plane after the operation; however, due to limited time, our data included only short-term follow-up cases (3 months after the operation). Because the short-term refractive state may be unstable, errors may have occurred. If postoperative refraction can be measured multiple times, the accuracy of the study can be improved. Another limitation is that the sample size was too small, and we only compared the data of the 3 mm to 5 mm annular area centered on the pupil, without analyzing the differences of other diameters or the annular area centered on the corneal apex; therefore, we could not conduct a comprehensive analysis and provide more reliable data support. In addition, we evaluated corneal refractive power only after surgery and did not verify these findings in eyes that had undergone SMILE surgery before cataract surgery. Therefore, more extensive research is required to verify and optimize these results.\u003c/p\u003e"},{"header":"Conclusion","content":"\u003cp\u003eAlthough Pentacam is the most accurate method for measuring TCRP4mm after corneal refractive surgery, it requires further verification and improvement before it can be widely used in combination with the existing intraocular lens calculation formula.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e \u003cstrong\u003eEthics approval and consent to participate\u003c/strong\u003e \u003cp\u003e The research protocol was approved by the Ethics Committee of the Second Hospital of Hebei Medical University, and the research was conducted in accordance with the Declaration of Helsinki. Given the prospective design of the research, written informed consent was obtained from all participants and approved by the Ethics Committee of the Second Hospital of Hebei Medical University.\u003c/p\u003e \u003c/p\u003e \u003cp\u003e \u003cstrong\u003eHuman ethics and informed consent statement\u003c/strong\u003e \u003cp\u003eApplicable\u003c/p\u003e \u003c/p\u003e \u003cp\u003e \u003cstrong\u003eCompeting interests\u003c/strong\u003e \u003cp\u003eThe authors declare no competing interests.\u003c/p\u003e \u003ch2\u003eFunding\u003c/h2\u003e \u003cp\u003eThis research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.\u003c/p\u003e\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eConceptualization: C. S., X.G.,B.Z.; Methodology: X.G.,B.Z.; Clinical studiesdemonstrate:C. S., S. S.; Data curation:C. S., S. S.; Formal analysis: X.G.,B.Z.,T.J.,C.T.; Writing-original draft preparation: S. S.; Writing-review and editing: C. S.; Supervision: X.G.,B.Z.\u003c/p\u003e\u003ch2\u003eAcknowledgement\u003c/h2\u003e\u003cp\u003eFirst and foremost, I would like to express my sincere gratitude to my supervisor, Professor Xiujin Guo, for her invaluable guidance, constant encouragement, and profound insights throughout the entire research process. From the initial conception of this study to the final revision of the manuscript, Professor Xiujin Guo has spared no effort to provide constructive suggestions, which have significantly shaped the quality of this paper. her rigorous academic attitude and dedication to scientific research have set a brilliant example for me.I am also deeply indebted to all the members of the Siyu Song.TaoJin.Bing Zhang.Chunmei Tong for their generous help and stimulating discussions during the experiments. Their selfless sharing of expertise and technical support has made the completion of this research possible.I wish to extend my heartfelt thanks to the participants who volunteered to take part in this study. Their cooperation and patience are the foundation of this research. I also thank the staff of Hospital for their help in recruiting participants and collecting clinical data.Last but not least, I would like to thank my family for their unconditional love, understanding, and support. Their constant care and encouragement have given me the strength to overcome difficulties and stay committed to my research. This paper is dedicated to them.\u003c/p\u003e\u003ch2\u003eData Availability\u003c/h2\u003e\u003cp\u003eThe datasets generated during the current study are available from the corresponding author upon reasonable request.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eIvarsen A, Asp S, Hjortdal J. Safety and complications of more than 1500 small-incision lenticule extraction procedures. Ophthalmology. 2014;121(4):822\u0026ndash;8.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eHansen RS, Lyhne N, Grauslund J, et al. Small-incision lenticule extraction (SMILE): outcomes of 722 eyes treated for myopia and myopic astigmatism. Graefes Arch Clin Exp Ophthalmol. 2016;254(2):399\u0026ndash;405.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eKamiya K, Shimizu K, Igarashi A, et al. Visual and refractive outcomes of femtosecond lenticule extraction and small-incision lenticule extraction for myopia. Am J Ophthalmol. 2014;157(1):128\u0026ndash;34.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eKoch DD, Liu JF, Hyde LL, et al. Refractive complications of cataract surgery after radial keratotomy. Am J Ophthalmol. 1989;108(6):676\u0026ndash;82.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLyle WA, Jin GJ. Intraocular lens power prediction in patients undergoing cataract surgery after radial keratotomy. Arch Ophthalmol. 1997;115(4):457\u0026ndash;61.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSeitz B, Langenbucher A, Nguyen NX, et al. Underestimation of intraocular lens power for cataract surgery after myopic photorefractive keratectomy. Ophthalmology. 1999;106(4):693\u0026ndash;702.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eGimbel H, Sun R, Kaye GB. Refractive errors in cataract surgery after previous refractive surgery. J Cataract Refract Surg. 2000;26(1):142\u0026ndash;4.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLesher MP, Schumer DJ, Hunkeler JD, et al. Phacoemulsification with intraocular lens implantation after excimer photorefractive keratectomy: A case report. J Cataract Refract Surg. 1994;20:265\u0026ndash;7.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eKalski RS, Danjoux JP, Fraenkel GE, Rogers C, et al. Intraocular lens power calculation for cataract surgery after photorefractive keratectomy in patients with high myopia. J Refract Surg. 1997 Jul-Aug;13(4):362\u0026ndash;6.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eGimbel HV, Sun R. Accuracy and predictability of intraocular lens power calculation after laser in situ keratomileusis. J Cataract Refract Surg. 2001;27(4):571\u0026ndash;6.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eCua IY, Qazi MA, Lee SF. Intraocular lens calculations in patients with corneal scarring and irregular astigmatism. J Cataract Refract Surg. 2003;29(7):1352\u0026ndash;7.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eOlsen T. Calculation of intraocular lens power: a review. Acta Ophthalmol Scand. 2007;85(5):472\u0026ndash;85.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eHo JD, Tsai CY, Tsai RJ, et al. Validity of the keratometric index: evaluation by the Pentacam rotating Scheimpflug camera. J Cataract Refract Surg. 2008;34(1):137\u0026ndash;45.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSavini G, Barboni P, Carbonelli M, et al. Agreement between Pentacam and videokeratography in corneal power assessment. J Refract Surg. 2009;25(6):534\u0026ndash;8.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eKopacz D, Maciejewicz P, Kecik D. Pentacam\u0026ndash;nowe mozliwości obrazowania przedniego odcinka gałki ocznej [Pentacam\u0026ndash;the new way for anterior eye segment imaging and mapping]. Klin Oczna. 2005;107(10\u0026ndash;12):728\u0026thinsp;\u0026ndash;\u0026thinsp;31.​.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eChen D, Lam AK. Intrasession and intersession repeatability of the Pentacam system for posterior corneal assessment in normal human eyes. J Cataract Refract Surg. 2007;33(3):448\u0026ndash;54.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBland JM, Altman DG. Statistical methods for assessing the agreement between two clinical measurement methods. Lancet. 1986;1(8476):307\u0026ndash;10.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eShammas HJ, Shammas MC, Garabet A, et al. Correcting corneal power measurements for intraocular lens power calculations after myopic laser in situ keratomileusis. Am J Ophthalmol. 2003;136(3):426\u0026ndash;32.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eKim JH, Lee Do, Joo CK. Measuring corneal power for intraocular lens power calculation after refractive surgery. Comparison of methods. J Cataract Refract Surg. 2002;28(11):1932. 8.​.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eWang L, Booth MA, Koch DD. Comparison of intraocular lens power calculation methods in eyes that underwent LASIK. Ophthalmology. 2004;111(10):1825\u0026ndash;31.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSavini G, Hoffer KJ, Carbonelli M. Scheimpflug analysis of corneal power changes after myopic excimer laser surgery. J Cataract Refract Surg. 2013;39(4):605\u0026ndash;10.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eOh JH, Kim SH, Chuck RS. Evaluation of the Pentacam ray tracing method for measuring central corneal power after myopic photorefractive keratectomy. Cornea. 2014;33(3):261\u0026ndash;5.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSavini G, Calossi A, Camellin M, et al. Corneal ray-tracing versus simulated keratometry for estimating corneal power changes after excimer laser surgery. J Cataract Refract Surg. 2014;40(7):1109\u0026ndash;15.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eCao JX, Liu W, Liu Y, et al. Comparison of corneal refractive power measurements between Pentacam and IOL Master [J]. Int Eye Sci. 2019;19(1):113\u0026ndash;7.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eElbaz U, Barkana Y, Gerber Y, et al. Comparison of different techniques for measuring the anterior chamber depth and keratometry. Am J Ophthalmol. 2007;143(1):48\u0026ndash;53.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003ePan H, Wang LH, Ma LX. Comparison of Pentacam and IOLMaster in measuring corneal curvature and anterior chamber depth. J Shandong Univ (Health Sciences). 2008;46:624\u0026ndash;7.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLi Lixin. Atlas of Ocular Ultrasound Diagnosis [Book]. Beijing: People's Medical Publishing House; 2003. pp. 22\u0026ndash;3.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLiu Houcang K, Ning. A study on the accuracy of Pentacam in measuring corneal refractive power after corneal refractive surgery [J]. J Clin Ophthalmol. 2016;24(6):538\u0026ndash;41.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eYanjun H, Jinhai H, Chao P, et al. Evaluation of total corneal power and prediction of intraocular lens power in patients after laser in situ keratomileusis [J]. Natl Med J China. 2012;92(33):2339\u0026ndash;44.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBorasio E, Stevens J, Smith GT. Estimation of true corneal power after keratorefractive surgery in eyes requiring cataract surgery: the BESSt formula. J Cataract Refract Surg. 2006;32(12):2004\u0026ndash;14.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eQian Y, Liu Y, Zhou X, et al. Comparison of Corneal Power and Astigmatism between Simulated Keratometry, True Net Power, and Total Corneal Refractive Power before and after. SMILE Lenticule Extr. 2017;2017:9659481.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSavini G, Barboni P, Profazio V. Corneal power measurements using the Pentacam Scheimpflug camera after myopic excimer laser surgery. J Cataract Refract Surg. 2008;34(5):809\u0026ndash;13.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMello GR, Roberts CJ, Smadja D, et al. Comparison of keratometric changes after myopic ablation: ray-tracing versus simulated keratometry. J Refract Surg. 2013;29(9):604\u0026ndash;10.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eWang L, Mahmoud AM, Anderson BL, et al. Total corneal power estimation: ray-tracing method versus Gaussian optics formula. Invest Ophthalmol Vis Sci. 2011;52(3):1716\u0026ndash;22.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eGyldenkerne A, Ivarsen A, Hjortdal J\u0026Oslash;. Assessing corneal power changes after refractive surgery using Scheimpflug imaging. Ophthalmic Physiol Opt. 2015;35(3):299\u0026ndash;307.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSrivannaboon S, Reinstein DZ, Sutton HF, et al. Accuracy of Orbscan total optical power maps in detecting refractive change after myopic laser in situ keratomileusis. J Cataract Refract Surg. 1999;25(12):1596\u0026ndash;9.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eS\u0026oacute;nego-Krone S, L\u0026oacute;pez-Moreno G, Beaujon-Balbi OV. Direct method for measuring the power of the central cornea after myopic laser in situ keratomileusis. Arch Ophthalmol. 2004;122(2):159\u0026ndash;66.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSavini G, Barboni P, Carbonelli M, et al. Accuracy of corneal power measurements by a new Scheimpflug camera combined with Placido-disk corneal topography for intraocular lens power calculation in unoperated eyes. J Cataract Refract Surg. 2012;38(5):787\u0026ndash;92.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eHirayama M, Wang L, Koch DD, et al. Comparison of accuracy of intraocular lens calculations using automated keratometry, a Placido-based corneal topographer, and a combined Placido-based and dual Scheimpflug corneal topographer. Cornea. 2010;29(10):1136\u0026ndash;8.\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"},{"header":"Tables","content":"\u003cp\u003eTable 1 to 5 are available in the Supplementary Files section.\u003c/p\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Refractive outcomes following corneal refractive surgery, simulated keratometry indices, calculation of true net power, assessment of equivalent keratometry, total corneal refractive power measured by ray tracing","lastPublishedDoi":"10.21203/rs.3.rs-8602154/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-8602154/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003ch2\u003eObjective\u003c/h2\u003e \u003cp\u003eThe main purpose of this study is to investigate the changes of corneal focusing ability after SMILE surgery. We used various measurement methods and collected a lot of information to study this problem. The results of the study aim to provide specific details to help ophthalmologists choose the most suitable intraocular lens for those who have cataract and have undergone vision correction surgery before.\u003c/p\u003e\u003ch2\u003eMethods\u003c/h2\u003e \u003cp\u003eFrom September 2020 to January 2021, we conducted a clinical study on 37 people (70 eyes) who had undergone SMILE surgery in Myopia Laser Treatment Center of our hospital. All participants came back for reexamination within three months after the operation. We made a comprehensive examination before and after the operation, including subjective and objective optometry, IOLMaster biometrics and Pentacam anterior segment imaging. Pentacam equipment generated data of SimK, TNP and TCRP, and equivalent corneal curvature readings (EKR) with diameters of 3 mm, 4 mm and 5 mm, and each measurement was centered on the pupil. The Km value is obtained from the evaluation of IOL Master. We compared and analyzed the refractive changes (△SimK, △TNP, △TCRP, △EKR and △Km) after operation with the refractive changes (△SE) on corneal surface. SPSS 22.0 software is used for statistical processing, including Kolmogorov-Smirnov test to see whether the data is normally distributed, variance analysis, paired t test and Pearson correlation analysis.\u003c/p\u003e\u003ch2\u003eResults\u003c/h2\u003e \u003cp\u003eAccording to SMILE procedure, the measurement results of TCRP4 mm and EKR4.5 mm remained stable, and no obvious changes were found (P\u0026thinsp;\u0026gt;\u0026thinsp;0.05). There was no obvious relationship between the change of TCRP4 mm (△TCRP4 mm) and the change of spherical lens degree (△SE) (P\u0026thinsp;\u0026gt;\u0026thinsp;0.05). However, there is a strong correlation between △TCRP4 mm and △SE, and the correlation coefficient is r\u0026thinsp;=\u0026thinsp;0.989. In addition, the consistency among △TCRP5 mm, △TCRP4 mm and △SE is also very high, and the 95% consistency ranges from \u0026minus;\u0026thinsp;0.47 to 0.11 D and \u0026minus;\u0026thinsp;0.32 to 0.50 D respectively.\u003c/p\u003e\u003ch2\u003eConclusion\u003c/h2\u003e \u003cp\u003eAlthough Pentacam is the most accurate method for measuring TCRP4mm after corneal refractive surgery, it requires further verification and improvement before it can be widely used in combination with the existing intraocular lens calculation formula.\u003c/p\u003e","manuscriptTitle":"Analysis of Corneal Refractive Power Following SMILE Procedure","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-01-24 00:40:25","doi":"10.21203/rs.3.rs-8602154/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"597b5a79-42ec-4dcc-a143-640569ccdc9e","owner":[],"postedDate":"January 24th, 2026","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2026-04-17T09:08:57+00:00","versionOfRecord":[],"versionCreatedAt":"2026-01-24 00:40:25","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-8602154","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-8602154","identity":"rs-8602154","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}