Effect of Q-Value Individualized CLEAR Kerato-refractive Lenticule Extraction Profile on Corneal Asphericity, Spherical Aberration, and Optical Zone Stability

Effect of Q-Value Individualized CLEAR Kerato-refractive Lenticule Extraction Profile on Corneal Asphericity, Spherical Aberration, and Optical Zone Stability | 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 Article Effect of Q-Value Individualized CLEAR Kerato-refractive Lenticule Extraction Profile on Corneal Asphericity, Spherical Aberration, and Optical Zone Stability Janne J. Järvenpää This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6404168/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 19 Aug, 2025 Read the published version in Scientific Reports → Version 1 posted 11 You are reading this latest preprint version Abstract Refractive surgery enhances visual performance by reshaping the cornea; however, preserving its natural asphericity is essential to minimizing induced optical aberrations. This study aims to evaluate the effect of Corneal Lenticule Extraction for Advanced Refractive Correction (CLEAR) on corneal asphericity, spherical aberration (SA) and effective optical zone (EOZ). Sixty eyes of 30 patients underwent refractive correction for myopia or compound myopic astigmatism with the CLEAR application, which considers individual Q-value to preserve corneal asphericity. Three months postoperatively, the uncorrected distance visual acuity (UDVA) was − 0.02 ± 0.06 LogMAR, the corrected distance visual acuity (CDVA) was − 0.04 ± 0.05 LogMAR and the manifest spherical equivalent refraction (MRSE) was 0.00 ± 0.34 D. The Q-value increased from − 0.13 ± 0.09 to 0.01 ± 0.27, resulting in an oblate shift of 0.14 ± 0.25 from the preoperative state. The preoperative SA was 0.24 ± 0.06 µm, remaining stable at 0.24 ± 0.13 µm postoperatively. The planned optical zone of 6.50 mm resulted in an achieved EOZ of 5.93 ± 0.40 mm, a mean reduction of -0.57 ± 0.40 mm. Myopia and compound myopic astigmatism correction with CLEAR therefore resulted in minimal positive shift in Q-value, limited EOZ reduction, and no overall induction of spherical aberration. Health sciences/Medical research/Study design/Clinical trials Health sciences/Medical research/Outcomes research CLEAR lenticule extraction Q-value Asphericity KLEx Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Introduction Optimizing postoperative visual quality in refractive surgery requires maintaining corneal asphericity, as oblate changes in corneal shape (positive Q-value shifts) are associated with the induction of spherical aberration (SA) and reduced effective optical zone (EOZ) 1 – 7 . These alterations have been linked to visual disturbances under mesopic conditions, such as glare, halos, ghost images, and reduced contrast sensitivity 8 – 10 . In both excimer laser and KLEx surgery, increases in Q-value are associated with smaller postoperative EOZs, emphasizing the need to minimize alterations in corneal shape 4 – 7 . Positive shifts in Q-value following kerato-refractive lenticule extraction (KLEx) surgery have also been associated with increased SA 7 , 11 , contributing to degraded vision in dim light conditions 12 , 13 . To address these challenges, the CLEAR procedure incorporates a Q-value–individualized aspheric resection profile designed to preserve the original corneal asphericity. Custom-Q laser ablation profiles for myopia correction have been proposed to limit the postoperative shift toward a more oblate corneal shape, thereby reducing SA induction and minimizing EOZ reduction 14 – 16 . However, the effect of such aspheric profiles in lenticule extraction surgery remains to be fully evaluated. This study aims to assess the consequences of the CLEAR procedure on corneal asphericity (Q-value change), SA and EOZ at 3 months post-surgery. RESULTS Thirty patients (60 eyes) were included in the study. Table 1 shows the preoperative characteristics of patients. Smooth lenticule interfaces dissection and lenticule removal were achieved in all cases with no difficulties. No intraoperative or postoperative complications were observed. Table 2 shows the refractive and visual outcomes at 3 months after the surgery, when the mean UDVA and CDVA were -0.02 ± 0.06 LogMAR and -0.04 ± 0.05 LogMAR, respectively, and spherical equivalent refraction was 0.00 ± 0.34 D. Figure 2a shows the mean pre- and post-CLEAR Q-value for the anterior corneal surface. The mean Q-value before surgery was -0.13 ± 0.09 (ranging from -0.32 to 0.10) indicating a prolate shape of the average cornea observed in operated subjects. After CLEAR, the mean Q-value shifted to an oblate shape of the cornea with a mean value of 0.01 ± 0.27 (ranging from -0.53 to 0.66). The mean positive increase in Q-value after the surgery was 0.14 ± 0.25 (ranging from -0.42 to 0.80). The mean preoperative SA for the anterior corneal surface was 0.24 ± 0.06 µm (ranging from 0.12 µm to 0.40 µm) and the mean SA at 3 months after CLEAR surgery was 0.24 ± 0.13 µm (ranging from 0.00 µm to 0.54 µm) (Figure 2b). No statistical difference in the amount of SA was observed between those two values. The mean POZ was 6.50 ± 0.00 mm and the mean EOZ at 3 months after CLEAR surgery was 5.93 ± 0.40 mm (ranging from 5.17 mm to 6.74 mm) (Figure 2c). The mean difference between POZ and EOZ was -0.57 ± 0.40 mm (ranging from -1.33 mm to 0.24 mm). A very strong, statistically significant, positive linear correlation was found between the induction of SA and change in Q-value (r = 0.865; p < 0.001) (Figure 3a). A moderate, statistically significant, negative correlation was found between the EOZ reduction and change in Q-value (r = -0.519; p < 0.001) (Figure 3b). Simple linear regressions analysis and correlation analysis were performed to explore the relationship between changes in Q-value, induced SA and EOZ reduction with preoperative MRSE (Figure 4). Changes in Q-value, induced SA and EOZ reduction were all statistically significantly correlated to preoperative MRSE. Changes in Q-value showed a moderate positive correlation (r = 0.496; p < 0.001) with preoperative MRSE. Induced SA showed a strong positive correlation with preoperative MRSE (r = 0.694, p < 0.001) and EOZ showed a strong negative correlation with preoperative MRSE (r = -0.684; p < 0.001). Finally, a weak positive correlation was found between the preoperative manifest refractive cylinder (MRCYL) and reduction in the EOZ (r = 0.268; p = 0.039) (Figure 5). Table 1. Preoperative characteristics (n = 60 eyes). Age (years) Mean (SD) Range 31.30 (4.77) 21, 39 Preop CDVA (LogMAR) Mean (SD) Range -0.04 (0.04) 0.05, -0.08 Preop sphere (D) Mean (SD) Range -2.70 (1.71) -0.50, -8.25 Preop cylinder (D) Mean (SD) Range -0.91 (0.68) 0.00, -3.75 Preop MRSE (D) Mean (SD) Range -3.15 (1.69) -0.75, -8.50 Table 2. Refraction and Visual Acuity at 3 months (n = 60 eyes). CDVA (LogMAR) Mean (SD) Range -0.04 (0.05) 0.10, -0.08 UDVA (LogMAR) Mean (SD) Range -0.02 (0.06) 0.15, -0.08 MRSE (D) Mean (SD) Range 0.00 (0.34) 1.00, -0.75 DISCUSSION Aspheric algorithms designed to compensate for the spherical aberrations induced by standard corneal laser ablation profiles provide clinically equivalent advantages to wavefront-guided profiles in terms of safety and refractive efficacy 14 , 16 , 17 , and lead to improved visual outcomes 18 . The current study examines changes in corneal asphericity, induced spherical aberration (SA), and effective optical zone (EOZ) following the use of an individualized aspheric femtosecond laser resection profile integrated in the CLEAR application. This aspheric profile is specifically designed to preserve the preoperative Q-value of the cornea, thereby minimizing postoperative shape alterations. Our analysis focused on the anterior corneal surface, as previous studies on lenticule extraction surgery have reported minimal changes in Q-value and limited induction of higher-order aberrations (HOAs) in the posterior corneal surface following the procedure 11 , 12 , 19 . In the study at hand, analyses were performed 3 months after CLEAR treatment, when EOZ is typically considered stable 20 , 21 . Furthermore, studies on changes in corneal asphericity after laser in situ keratomileusis (LASIK) showed stable asphericity data after 3 months 3 . The first notable finding of this study is the low amount of oblate shift in anterior corneal Q-value observed after CLEAR (+ 0.14) compared to previously reported lenticule extraction on other platforms 11 , 22 , 23 . Zhang et al. showed a mean positive change of Q-value of the anterior corneal surface of about + 1.0 at 6 months after surgery 11 while Yu et al. observed a mean positive increase of Q-value of around + 0.8 at 3 months after surgery 23 . The Q-value aspheric algorithm implemented in CLEAR and aimed at preserving the preoperative anterior corneal asphericity may explain the limited amount of positive increase in Q-value. Several studies on laser refractive surgery have identified changes in corneal asphericity as a key factor in SA increase 24 – 26 . In line with this, we observed a strong linear correlation between the change in Q-value and induced SA. However, since the average change in Q-value was minimal, there was no overall induction of SA post-surgery. We also observed a strong correlation between preoperative MRSE and EOZ reduction, in agreement with previous lenticule extraction studies 7 , 21 . Also consistent with published reports is the observation that the smaller the increase in Q-value, the less the reduction in EOZ 6 , 7 . The mean reduction in EOZ diameter observed in this study (0.57 mm) compares favorably with published results obtained on different lenticule extraction laser platforms using comparable preoperative MRSE and set POZ, where EOZ reduction ranged from 1.16 mm to 1.45 mm 6 , 7 , 20 , 27 . The individualized resection profile in CLEAR likely contributes to minimizing the oblate shift in Q-value and the associated reduction in EOZ, similar to how aspheric ablation profiles in LASIK have been shown to result in larger EOZs than conventional ablation profiles. 15 , 28 . A limitation of the current study is that the specific contribution of the aspheric profile was not directly assessed, as it is a built-in feature of the CLEAR application. In conclusion, the modest positive change in Q-value following CLEAR surgery was correlated with both induced SA and EOZ reduction, confirming previous observations. The Q-value–individualized aspheric femtosecond laser resection profile in the CLEAR application appears effective in preserving preoperative anterior corneal asphericity, thereby limiting postoperative SA induction and minimizing EOZ reduction. METHODS Data from 30 patients (60 eyes) having undergone KLEx surgery at the Silmäsairaala Pilke Eye Clinic in Tampere, Finland, from February 2023 to June 2023, were used within a context of a retrospective, consecutive case-series study data analysis. Included patients were 21 years of age or older, had stable refraction over the past year, preoperative corrected distance visual acuity (CDVA) of 20/25 or better, myopia or compound myopic astigmatism with manifest refraction spherical equivalent (MRSE) of -0.75 diopter (D) to -8.50 D, manifest sphere up to -8.25 D, manifest cylinder up to -3.75 D, had no ocular or systemic diseases and presented to follow-up examinations at 3 months postoperatively. Soft contact lens wearers were advised to stop wearing their lenses at least two weeks before surgery. The study was approved by the Ethics Committee of Finland (approval No.FIN-20231201). All patients were informed about the surgical procedure and provided written informed consent, including consent for inclusion of their data in research. This research followed the tenets of the Declaration of Helsinki. Preoperative and postoperative evaluation All patients were evaluated in the clinic following a standard preoperative assessment for refractive surgery. A full ophthalmic examination was performed, including monocular uncorrected distance visual acuity (UDVA) and CDVA measurement, subjective and manifest refraction, pupillometry in scotopic conditions, slit-lamp evaluation, corneal topography and tomography, corneal pachymetry, OCT, tonometry and fundoscopy. Postoperative data consisted of UDVA, CDVA, manifest refraction and corneal topography and tomography. Corneal asphericity and corneal spherical aberration measurement Preoperative and postoperative Q-value and SA measurements were performed with the Scheimpflug tomography system (GALILEI G6, Ziemer Ophthalmic Systems AG, Port, Switzerland) under scotopic conditions. To minimize the potential effect of tear film on corneal imaging, patients were required to keep fixating on a target immediately after a blink. Corneal SA and corneal asphericity (Q-value) were analyzed for the anterior corneal surface. SA data were analyzed over a 6.0 mm central diameter and Q-value over an 8.0 mm diameter. Effective optical zone measurement The anterior curvature difference maps between the preoperative and postoperative measurements were obtained using the Scheimpflug tomography system and the EOZ defined as the area outlined by a change of 0.00 D 29 , 30 . The mean EOZ diameter was defined as the average value of the diameters that were measured from 6 different corneal meridians at 30-degree intervals (Fig. 1 ) according to a procedure described elsewhere 6 . Surgical Technique The same surgeon (J. J. J.) performed all the surgeries. CLEAR treatments were performed using the low energy FEMTO LDV Z8 femtosecond laser platform (Ziemer Ophthalmic Systems AG, Port, Switzerland). The individual Q-value was entered for each patient's eyes to allow the CLEAR algorithm to generate a personalized, aspheric resection profile. The default lenticule cap thickness was 120 µm but was occasionally reduced to meet the residual stromal thickness limit of 250 µm. The programmed optical zone (POZ) diameter was 6.5 mm in all cases. A 3.0 mm access incision was created at 12 o’clock. Intraoperative adjustment for cyclotorsion and lenticule centration on the first Purkinje reflex was performed in all cases by marking the cornea at the slit-lamp along the horizontal and vertical meridians. After suction application, the horizontal and vertical meridians’ corneal marks (the marks were created to bisect the first Purkinje reflex) were used to align the axis of the lenticule treatment. The surgeon’s personalized nomogram based on attempted refractive correction, corneal curvature and patient age was used in the planning of all treatments 31 . The lenticule dissection and extraction was performed using a standard technique described in detail in the literature 32 . Postoperative medications included dexamethasone (1 mg/ml) and chloramphenicol (2 mg/ml) 4 times daily for 2 weeks. No intraoperative or postoperative complications were observed. Statistical methods For descriptive statistical analysis and graphs (means and standard deviations), Microsoft Excel (2016, Microsoft Corporation, Redmond, WA) was used. All simple linear regressions, Shapiro-Wilk normality tests, Student’s t-tests and Pearson correlation analyses were conducted using R Software (R version 4.1.1, Vienna, Austria). Declarations Disclosure statement : The author has no financial or proprietary interest in any material or method mentioned. There has been no financial support for this work. Ethics approval and consent to participate The study was approved by the Ethics Committee of Finland (approval No.FIN-20231201). This research followed the tenets of the Declaration of Helsinki. Consent for publication All patients were informed about the surgical procedure and provided written informed consent, including consent for inclusion of their data in research Funding The authors declare that they have no competing interests Author Contribution Janne J Järvenpää has done the article, collected the data and operated the customers. Data Availability The datasets used and/or analyzed during the current study are available from the corresponding author on reasonable request. Competing interests This study received no external funding. References Henslee, S. L. & Rowsey, J. J. New corneal shapes in keratorefractive surgery. Ophthalmology 90 , 245-250, doi:10.1016/s0161-6420(83)34567-x (1983). Patel, S., Marshall, J. & Fitzke, F. W., 3rd. Model for predicting the optical performance of the eye in refractive surgery. Refract Corneal Surg 9 , 366-375 (1993). Anera, R. G., Jiménez, J. 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Additional Declarations No competing interests reported. Cite Share Download PDF Status: Published Journal Publication published 19 Aug, 2025 Read the published version in Scientific Reports → Version 1 posted Editorial decision: Revision requested 01 Jul, 2025 Reviews received at journal 05 Jun, 2025 Reviewers agreed at journal 04 Jun, 2025 Reviewers agreed at journal 04 Jun, 2025 Reviews received at journal 21 May, 2025 Reviewers agreed at journal 06 May, 2025 Reviewers invited by journal 28 Apr, 2025 Editor assigned by journal 26 Apr, 2025 Editor invited by journal 16 Apr, 2025 Submission checks completed at journal 15 Apr, 2025 First submitted to journal 08 Apr, 2025 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. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-6404168","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":450616196,"identity":"e489fe3e-951d-42bd-93e5-b63c3c666ac3","order_by":0,"name":"Janne J. Järvenpää","email":"data:image/png;base64,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","orcid":"","institution":"Silmäsairaala Pilke Eye Clinic","correspondingAuthor":true,"prefix":"","firstName":"Janne","middleName":"J.","lastName":"Järvenpää","suffix":""}],"badges":[],"createdAt":"2025-04-08 14:08:28","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-6404168/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-6404168/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1038/s41598-025-16271-3","type":"published","date":"2025-08-19T16:12:52+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":82139981,"identity":"20db7959-021c-4c3d-b9e5-f3052fa4c4a1","added_by":"auto","created_at":"2025-05-07 06:29:00","extension":"jpg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":400206,"visible":true,"origin":"","legend":"\u003cp\u003eEffective optical zone (EOZ) measurement at different corneal meridians on the tangential curvature difference map generated by the Scheimpflug tomography system.\u003c/p\u003e","description":"","filename":"Figure1.tiff.jpg","url":"https://assets-eu.researchsquare.com/files/rs-6404168/v1/9d0c2fbdd7b5d9d21f5bcb32.jpg"},{"id":82139986,"identity":"c90c074e-a97e-4462-930a-662a89bd2472","added_by":"auto","created_at":"2025-05-07 06:29:00","extension":"jpg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":422775,"visible":true,"origin":"","legend":"\u003cp\u003e(a) Corneal asphericity of the anterior corneal surface preoperatively and 3 months after CLEAR. There was significant difference between pre- and post-CLEAR in the changes of Q-value (Student’s t-test, p \u0026lt; 0.001, n = 60 eyes). (b) Spherical aberration of the anterior corneal surface preoperatively and 3 months after CLEAR. There was no significant difference between pre- and post-CLEAR in the changes of spherical aberration (Student’s t-test, p = 0.901, n = 60 eyes). (c) Programmed optical zone (OZ) and effective optical zone (EOZ) 3 months after CLEAR. There was significant difference between the programmed OZ and the EOZ (Student’s t-test, p \u0026lt; 0.001, n = 60 eyes).\u003c/p\u003e","description":"","filename":"Figure2.tif.jpg","url":"https://assets-eu.researchsquare.com/files/rs-6404168/v1/331cccaf7a57a1e1e530fec1.jpg"},{"id":82139988,"identity":"ddd87eb0-6747-4e31-92da-5d9bb3e66e91","added_by":"auto","created_at":"2025-05-07 06:29:00","extension":"jpg","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":448275,"visible":true,"origin":"","legend":"\u003cp\u003e(a) Correlation between post-surgery induced spherical aberration (SA) and change in Q-value. (b) Correlation between effective optical zone (EOZ) reduction and change in Q-value. n = 60 eyes.\u003c/p\u003e","description":"","filename":"Figure3.tif.jpg","url":"https://assets-eu.researchsquare.com/files/rs-6404168/v1/3d5d55bea2fb0710a326cef8.jpg"},{"id":82139985,"identity":"b7bcc722-0e40-4642-9de7-0f0ab650d913","added_by":"auto","created_at":"2025-05-07 06:29:00","extension":"jpg","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":538094,"visible":true,"origin":"","legend":"\u003cp\u003e(a) Change in corneal asphericity (Q-value) plotted as function of preoperative manifest refraction spherical equivalent (MRSE) 3 months after CLEAR. (b) Induced spherical aberration (SA) plotted as function of preoperative manifest refraction spherical equivalent (MRSE) 3 months after CLEAR. (c) Reduction in the effective optical zone (EOZ) plotted as function of preoperative manifest refraction spherical equivalent (MRSE) 3 months after CLEAR. n = 60 eyes\u003c/p\u003e","description":"","filename":"Figure4.tif.jpg","url":"https://assets-eu.researchsquare.com/files/rs-6404168/v1/b2a7392d7205dd9ebc21eebc.jpg"},{"id":82142135,"identity":"12889812-1334-491e-bfc0-2e8f69041c54","added_by":"auto","created_at":"2025-05-07 06:37:00","extension":"jpg","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":232986,"visible":true,"origin":"","legend":"\u003cp\u003eCorrelation between preoperative manifest refractive cylinder (MRCYL) and reduction in the effective optical zone (EOZ). The low R-squared value indicates that the EOZ reduction cannot be predicted by the amount of preoperative manifest refractive cylinder. n = 60 eyes\u003c/p\u003e","description":"","filename":"Figure5.tif.jpg","url":"https://assets-eu.researchsquare.com/files/rs-6404168/v1/a32c51f3d890d32b8eefaa27.jpg"},{"id":89847045,"identity":"7d47a0e1-e0bc-4e62-b2e4-d683d9b6eb8e","added_by":"auto","created_at":"2025-08-25 16:38:52","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":2649115,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-6404168/v1/2c55cbdb-a921-4f7c-a5b4-d9fe4d987aff.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Effect of Q-Value Individualized CLEAR Kerato-refractive Lenticule Extraction Profile on Corneal Asphericity, Spherical Aberration, and Optical Zone Stability","fulltext":[{"header":"Introduction","content":"\u003cp\u003eOptimizing postoperative visual quality in refractive surgery requires maintaining corneal asphericity, as oblate changes in corneal shape (positive Q-value shifts) are associated with the induction of spherical aberration (SA) and reduced effective optical zone (EOZ) \u003csup\u003e\u003cspan additionalcitationids=\"CR2 CR3 CR4 CR5 CR6\" citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e\u003c/sup\u003e. These alterations have been linked to visual disturbances under mesopic conditions, such as glare, halos, ghost images, and reduced contrast sensitivity \u003csup\u003e\u003cspan additionalcitationids=\"CR9\" citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e\u003c/sup\u003e. In both excimer laser and KLEx surgery, increases in Q-value are associated with smaller postoperative EOZs, emphasizing the need to minimize alterations in corneal shape\u003csup\u003e\u003cspan additionalcitationids=\"CR5 CR6\" citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e\u003c/sup\u003e. Positive shifts in Q-value following kerato-refractive lenticule extraction (KLEx) surgery have also been associated with increased SA \u003csup\u003e\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e,\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e\u003c/sup\u003e, contributing to degraded vision in dim light conditions\u003csup\u003e\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e,\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e\u003c/sup\u003e. To address these challenges, the CLEAR procedure incorporates a Q-value\u0026ndash;individualized aspheric resection profile designed to preserve the original corneal asphericity. Custom-Q laser ablation profiles for myopia correction have been proposed to limit the postoperative shift toward a more oblate corneal shape, thereby reducing SA induction and minimizing EOZ reduction \u003csup\u003e\u003cspan additionalcitationids=\"CR15\" citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e\u003c/sup\u003e. However, the effect of such aspheric profiles in lenticule extraction surgery remains to be fully evaluated. This study aims to assess the consequences of the CLEAR procedure on corneal asphericity (Q-value change), SA and EOZ at 3 months post-surgery.\u003c/p\u003e"},{"header":"RESULTS","content":"\u003cp\u003eThirty patients (60 eyes) were included in the study. Table 1 shows the preoperative characteristics of patients. Smooth lenticule interfaces dissection and lenticule removal were achieved in all cases with no difficulties. No intraoperative or postoperative complications were observed. Table 2 shows the refractive and visual outcomes at 3 months after the surgery, when the mean UDVA and CDVA were -0.02 \u0026plusmn; 0.06 LogMAR and -0.04 \u0026plusmn; 0.05 LogMAR, respectively, and spherical equivalent refraction was 0.00 \u0026plusmn; 0.34 D. Figure 2a shows the mean pre- and post-CLEAR Q-value for the anterior corneal surface. The mean Q-value before surgery was -0.13 \u0026plusmn; 0.09 (ranging from -0.32 to 0.10) indicating a prolate shape of the average cornea observed in operated subjects. After CLEAR, the mean Q-value shifted to an oblate shape of the cornea with a mean value of 0.01 \u0026plusmn; 0.27 (ranging from -0.53 to 0.66). The mean positive increase in Q-value after the surgery was 0.14 \u0026plusmn; 0.25 (ranging from -0.42 to 0.80). The mean preoperative SA for the anterior corneal surface was 0.24 \u0026plusmn; 0.06 \u0026micro;m (ranging from 0.12 \u0026micro;m to 0.40 \u0026micro;m) and the mean SA at 3 months after CLEAR surgery was 0.24 \u0026plusmn; 0.13 \u0026micro;m (ranging from 0.00 \u0026micro;m to 0.54 \u0026micro;m) (Figure 2b). No statistical difference in the amount of SA was observed between those two values. The mean POZ was 6.50 \u0026plusmn; 0.00 mm and the mean EOZ at 3 months after CLEAR surgery was 5.93 \u0026plusmn; 0.40 mm (ranging from 5.17 mm to 6.74 mm) (Figure 2c). The mean difference between POZ and EOZ was -0.57 \u0026plusmn; 0.40 mm (ranging from -1.33 mm to 0.24 mm). A very strong, statistically significant, positive linear correlation was found between the induction of SA and change in Q-value (r = 0.865; p \u0026lt; 0.001) (Figure 3a). A moderate, statistically significant, negative correlation was found between the EOZ reduction and change in Q-value (r = -0.519; p \u0026lt; 0.001) (Figure 3b). \u0026nbsp;Simple linear regressions analysis and correlation analysis were performed to explore the relationship between changes in Q-value, induced SA and EOZ reduction with preoperative MRSE (Figure 4). Changes in Q-value, induced SA and EOZ reduction were all statistically significantly correlated to preoperative MRSE. Changes in Q-value showed a moderate positive correlation (r = 0.496; p \u0026lt; 0.001) with preoperative MRSE. Induced SA showed a strong positive correlation with preoperative MRSE (r = 0.694, p \u0026lt; 0.001) and EOZ showed a strong negative correlation with preoperative MRSE (r = -0.684; p \u0026lt; 0.001). Finally, a weak positive correlation was found between the preoperative manifest refractive cylinder (MRCYL) and reduction in the EOZ (r = 0.268; p = 0.039) (Figure 5).\u003c/p\u003e\n\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\" width=\"344\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"2\" style=\"width: 100%;\"\u003e\n \u003cp\u003e\u003cstrong\u003eTable 1. Preoperative characteristics (n = 60 eyes).\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 50.8721%;\"\u003e\n \u003cp\u003e\u003cstrong\u003eAge (years)\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003eMean (SD)\u003c/p\u003e\n \u003cp\u003eRange\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 49.1279%;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e31.30 (4.77)\u003c/p\u003e\n \u003cp\u003e21, 39\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 50.8721%;\"\u003e\n \u003cp\u003e\u003cstrong\u003ePreop CDVA (LogMAR)\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003eMean (SD)\u003c/p\u003e\n \u003cp\u003eRange\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 49.1279%;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e-0.04 (0.04)\u003c/p\u003e\n \u003cp\u003e0.05, -0.08\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 50.8721%;\"\u003e\n \u003cp\u003e\u003cstrong\u003ePreop sphere (D)\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003eMean (SD)\u003c/p\u003e\n \u003cp\u003eRange\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 49.1279%;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e-2.70 (1.71)\u003c/p\u003e\n \u003cp\u003e-0.50, -8.25\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 50.8721%;\"\u003e\n \u003cp\u003e\u003cstrong\u003ePreop cylinder (D)\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003eMean (SD)\u003c/p\u003e\n \u003cp\u003eRange\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 49.1279%;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e-0.91 (0.68)\u003c/p\u003e\n \u003cp\u003e0.00, -3.75\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 50.8721%;\"\u003e\n \u003cp\u003e\u003cstrong\u003ePreop MRSE (D)\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003eMean (SD)\u003c/p\u003e\n \u003cp\u003eRange\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 49.1279%;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e-3.15 (1.69)\u003c/p\u003e\n \u003cp\u003e-0.75, -8.50\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003e\u0026nbsp;\u003c/p\u003e\n\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\" width=\"432\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"2\" style=\"width: 432px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eTable 2. Refraction and Visual Acuity at 3 months (n = 60 eyes).\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 194px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eCDVA (LogMAR)\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003eMean (SD)\u003c/p\u003e\n \u003cp\u003eRange\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 237px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e-0.04 (0.05)\u003c/p\u003e\n \u003cp\u003e0.10, -0.08\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 194px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eUDVA (LogMAR)\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003eMean (SD)\u003c/p\u003e\n \u003cp\u003eRange\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 237px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e-0.02 (0.06)\u003c/p\u003e\n \u003cp\u003e0.15, -0.08\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 194px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eMRSE (D)\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003eMean (SD)\u003c/p\u003e\n \u003cp\u003eRange\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 237px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e0.00 (0.34)\u003c/p\u003e\n \u003cp\u003e1.00, -0.75\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e"},{"header":"DISCUSSION","content":"\u003cp\u003eAspheric algorithms designed to compensate for the spherical aberrations induced by standard corneal laser ablation profiles provide clinically equivalent advantages to wavefront-guided profiles in terms of safety and refractive efficacy \u003csup\u003e\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e,\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e,\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e\u003c/sup\u003e, and lead to improved visual outcomes \u003csup\u003e\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e\u003c/sup\u003e. The current study examines changes in corneal asphericity, induced spherical aberration (SA), and effective optical zone (EOZ) following the use of an individualized aspheric femtosecond laser resection profile integrated in the CLEAR application. This aspheric profile is specifically designed to preserve the preoperative Q-value of the cornea, thereby minimizing postoperative shape alterations. Our analysis focused on the anterior corneal surface, as previous studies on lenticule extraction surgery have reported minimal changes in Q-value and limited induction of higher-order aberrations (HOAs) in the posterior corneal surface following the procedure \u003csup\u003e\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e,\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e,\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e\u003c/sup\u003e. In the study at hand, analyses were performed 3 months after CLEAR treatment, when EOZ is typically considered stable \u003csup\u003e\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e,\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e\u003c/sup\u003e. Furthermore, studies on changes in corneal asphericity after laser in situ keratomileusis (LASIK) showed stable asphericity data after 3 months \u003csup\u003e\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eThe first notable finding of this study is the low amount of oblate shift in anterior corneal Q-value observed after CLEAR (+\u0026thinsp;0.14) compared to previously reported lenticule extraction on other platforms \u003csup\u003e\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e,\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e,\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e\u003c/sup\u003e. Zhang et al. showed a mean positive change of Q-value of the anterior corneal surface of about\u0026thinsp;+\u0026thinsp;1.0 at 6 months after surgery \u003csup\u003e\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e\u003c/sup\u003e while Yu et al. observed a mean positive increase of Q-value of around +\u0026thinsp;0.8 at 3 months after surgery \u003csup\u003e\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e\u003c/sup\u003e. The Q-value aspheric algorithm implemented in CLEAR and aimed at preserving the preoperative anterior corneal asphericity may explain the limited amount of positive increase in Q-value. Several studies on laser refractive surgery have identified changes in corneal asphericity as a key factor in SA increase \u003csup\u003e\u003cspan additionalcitationids=\"CR25\" citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e\u003c/sup\u003e. In line with this, we observed a strong linear correlation between the change in Q-value and induced SA. However, since the average change in Q-value was minimal, there was no overall induction of SA post-surgery.\u003c/p\u003e \u003cp\u003eWe also observed a strong correlation between preoperative MRSE and EOZ reduction, in agreement with previous lenticule extraction studies \u003csup\u003e\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e,\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e\u003c/sup\u003e. Also consistent with published reports is the observation that the smaller the increase in Q-value, the less the reduction in EOZ \u003csup\u003e\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e,\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e\u003c/sup\u003e. The mean reduction in EOZ diameter observed in this study (0.57 mm) compares favorably with published results obtained on different lenticule extraction laser platforms using comparable preoperative MRSE and set POZ, where EOZ reduction ranged from 1.16 mm to 1.45 mm \u003csup\u003e\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e,\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e,\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e,\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e\u003c/sup\u003e. The individualized resection profile in CLEAR likely contributes to minimizing the oblate shift in Q-value and the associated reduction in EOZ, similar to how aspheric ablation profiles in LASIK have been shown to result in larger EOZs than conventional ablation profiles. \u003csup\u003e\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e,\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e\u003c/sup\u003e. A limitation of the current study is that the specific contribution of the aspheric profile was not directly assessed, as it is a built-in feature of the CLEAR application. In conclusion, the modest positive change in Q-value following CLEAR surgery was correlated with both induced SA and EOZ reduction, confirming previous observations. The Q-value\u0026ndash;individualized aspheric femtosecond laser resection profile in the CLEAR application appears effective in preserving preoperative anterior corneal asphericity, thereby limiting postoperative SA induction and minimizing EOZ reduction.\u003c/p\u003e"},{"header":"METHODS","content":"\u003cp\u003eData from 30 patients (60 eyes) having undergone KLEx surgery at the Silm\u0026auml;sairaala Pilke Eye Clinic in Tampere, Finland, from February 2023 to June 2023, were used within a context of a retrospective, consecutive case-series study data analysis. Included patients were 21 years of age or older, had stable refraction over the past year, preoperative corrected distance visual acuity (CDVA) of 20/25 or better, myopia or compound myopic astigmatism with manifest refraction spherical equivalent (MRSE) of -0.75 diopter (D) to -8.50 D, manifest sphere up to -8.25 D, manifest cylinder up to -3.75 D, had no ocular or systemic diseases and presented to follow-up examinations at 3 months postoperatively. Soft contact lens wearers were advised to stop wearing their lenses at least two weeks before surgery. The study was approved by the Ethics Committee of Finland (approval No.FIN-20231201). All patients were informed about the surgical procedure and provided written informed consent, including consent for inclusion of their data in research. This research followed the tenets of the Declaration of Helsinki.\u003c/p\u003e\n\u003ch3\u003ePreoperative and postoperative evaluation\u003c/h3\u003e\n\u003cp\u003eAll patients were evaluated in the clinic following a standard preoperative assessment for refractive surgery. A full ophthalmic examination was performed, including monocular uncorrected distance visual acuity (UDVA) and CDVA measurement, subjective and manifest refraction, pupillometry in scotopic conditions, slit-lamp evaluation, corneal topography and tomography, corneal pachymetry, OCT, tonometry and fundoscopy. Postoperative data consisted of UDVA, CDVA, manifest refraction and corneal topography and tomography.\u003c/p\u003e\n\u003ch3\u003eCorneal asphericity and corneal spherical aberration measurement\u003c/h3\u003e\n\u003cp\u003ePreoperative and postoperative Q-value and SA measurements were performed with the Scheimpflug tomography system (GALILEI G6, Ziemer Ophthalmic Systems AG, Port, Switzerland) under scotopic conditions. To minimize the potential effect of tear film on corneal imaging, patients were required to keep fixating on a target immediately after a blink. Corneal SA and corneal asphericity (Q-value) were analyzed for the anterior corneal surface. SA data were analyzed over a 6.0 mm central diameter and Q-value over an 8.0 mm diameter.\u003c/p\u003e\n\u003ch3\u003eEffective optical zone measurement\u003c/h3\u003e\n\u003cp\u003eThe anterior curvature difference maps between the preoperative and postoperative measurements were obtained using the Scheimpflug tomography system and the EOZ defined as the area outlined by a change of 0.00 D \u003csup\u003e\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e,\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e\u003c/sup\u003e. The mean EOZ diameter was defined as the average value of the diameters that were measured from 6 different corneal meridians at 30-degree intervals (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e1\u003c/span\u003e) according to a procedure described elsewhere \u003csup\u003e\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003eSurgical Technique\u003c/h2\u003e \u003cp\u003eThe same surgeon (J. J. J.) performed all the surgeries. CLEAR treatments were performed using the low energy FEMTO LDV Z8 femtosecond laser platform (Ziemer Ophthalmic Systems AG, Port, Switzerland). The individual Q-value was entered for each patient's eyes to allow the CLEAR algorithm to generate a personalized, aspheric resection profile. The default lenticule cap thickness was 120 \u0026micro;m but was occasionally reduced to meet the residual stromal thickness limit of 250 \u0026micro;m. The programmed optical zone (POZ) diameter was 6.5 mm in all cases. A 3.0 mm access incision was created at 12 o\u0026rsquo;clock. Intraoperative adjustment for cyclotorsion and lenticule centration on the first Purkinje reflex was performed in all cases by marking the cornea at the slit-lamp along the horizontal and vertical meridians. After suction application, the horizontal and vertical meridians\u0026rsquo; corneal marks (the marks were created to bisect the first Purkinje reflex) were used to align the axis of the lenticule treatment. The surgeon\u0026rsquo;s personalized nomogram based on attempted refractive correction, corneal curvature and patient age was used in the planning of all treatments \u003csup\u003e\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e\u003c/sup\u003e. The lenticule dissection and extraction was performed using a standard technique described in detail in the literature \u003csup\u003e\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e\u003c/sup\u003e. Postoperative medications included dexamethasone (1 mg/ml) and chloramphenicol (2 mg/ml) 4 times daily for 2 weeks. No intraoperative or postoperative complications were observed.\u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003eStatistical methods\u003c/h3\u003e\n\u003cp\u003eFor descriptive statistical analysis and graphs (means and standard deviations), Microsoft Excel (2016, Microsoft Corporation, Redmond, WA) was used. All simple linear regressions, Shapiro-Wilk normality tests, Student\u0026rsquo;s t-tests and Pearson correlation analyses were conducted using R Software (R version 4.1.1, Vienna, Austria).\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e \u003cspan type=\"Underline\" class=\"Underline\" name=\"Emphasis\"\u003eDisclosure statement\u003c/span\u003e: The author has no financial or proprietary interest in any material or method mentioned. There has been no financial support for this work.\u003c/p\u003e \u003c/p\u003e \u003cp\u003e \u003cstrong\u003eEthics approval and consent to participate\u003c/strong\u003e \u003cp\u003eThe study was approved by the Ethics Committee of Finland (approval No.FIN-20231201). This research followed the tenets of the Declaration of Helsinki.\u003c/p\u003e \u003c/p\u003e \u003cp\u003e \u003cstrong\u003eConsent for publication\u003c/strong\u003e \u003cp\u003eAll patients were informed about the surgical procedure and provided written informed consent, including consent for inclusion of their data in research\u003c/p\u003e \u003c/p\u003e\u003ch2\u003eFunding\u003c/h2\u003e \u003cp\u003eThe authors declare that they have no competing interests\u003c/p\u003e\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eJanne J J\u0026auml;rvenp\u0026auml;\u0026auml; has done the article, collected the data and operated the customers.\u003c/p\u003e\u003ch2\u003eData Availability\u003c/h2\u003e\u003cp\u003eThe datasets used and/or analyzed during the current study are available from the corresponding author on reasonable request.\u003c/p\u003e\u003cp\u003e\u003cu\u003eCompeting interests\u003c/u\u003e\u003c/p\u003e\n\u003cp\u003eThis study received no external funding.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eHenslee, S. 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Corneal Power Distribution and Functional Optical Zone Following Small Incision Lenticule Extraction for Myopia. \u003cem\u003eJ Refract Surg\u003c/em\u003e \u003cstrong\u003e31\u003c/strong\u003e, 532-538, doi:10.3928/1081597x-20150727-03 (2015).\u003c/li\u003e\n\u003cli\u003eHori-Komai, Y.\u003cem\u003e et al.\u003c/em\u003e Comparison of LASIK using the NIDEK EC-5000 optimized aspheric transition zone (OATz) and conventional ablation profile. \u003cem\u003eJ Refract Surg\u003c/em\u003e \u003cstrong\u003e22\u003c/strong\u003e, 546-555, doi:10.3928/1081-597x-20060601-06 (2006).\u003c/li\u003e\n\u003cli\u003eTabernero, J., Klyce, S. D., Sarver, E. J. \u0026amp; Artal, P. Functional optical zone of the cornea. \u003cem\u003eInvest Ophthalmol Vis Sci\u003c/em\u003e \u003cstrong\u003e48\u003c/strong\u003e, 1053-1060, doi:10.1167/iovs.06-0867 (2007).\u003c/li\u003e\n\u003cli\u003eDamgaard, I. B.\u003cem\u003e et al.\u003c/em\u003e Functional Optical Zone and Centration Following SMILE and LASIK: A Prospective, Randomized, Contralateral Eye Study. \u003cem\u003eJ Refract Surg\u003c/em\u003e \u003cstrong\u003e35\u003c/strong\u003e, 230-237, doi:10.3928/1081597x-20190313-01 (2019).\u003c/li\u003e\n\u003cli\u003eJ\u0026auml;rvenp\u0026auml;\u0026auml;, J. J. Impact Of Patients\u0026rsquo; Baseline Parameters On Refractive, Visual And Quality Of Vision Outcomes Of Corneal Lenticule Extraction For Advanced Refractive Correction (CLEAR) Procedure. \u003cem\u003e41st congress of the ESCRS, 8-12 September 2023, Vienna, Austria\u003c/em\u003e (Oral presentation).\u003c/li\u003e\n\u003cli\u003eReinstein, D. Z., Archer, T. J. \u0026amp; Carp, G. I. The Surgeon\u0026apos;s Guide to SMILE: Small Incision Lenticule Extraction. \u003cem\u003eSlack Incorporated\u003c/em\u003e (2018).\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"scientific-reports","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"scirep","sideBox":"Learn more about [Scientific Reports](http://www.nature.com/srep/)","snPcode":"","submissionUrl":"","title":"Scientific Reports","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Scientific Reports","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"CLEAR, lenticule extraction, Q-value, Asphericity, KLEx","lastPublishedDoi":"10.21203/rs.3.rs-6404168/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-6404168/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eRefractive surgery enhances visual performance by reshaping the cornea; however, preserving its natural asphericity is essential to minimizing induced optical aberrations. This study aims to evaluate the effect of Corneal Lenticule Extraction for Advanced Refractive Correction (CLEAR) on corneal asphericity, spherical aberration (SA) and effective optical zone (EOZ). Sixty eyes of 30 patients underwent refractive correction for myopia or compound myopic astigmatism with the CLEAR application, which considers individual Q-value to preserve corneal asphericity. Three months postoperatively, the uncorrected distance visual acuity (UDVA) was \u0026minus;\u0026thinsp;0.02\u0026thinsp;\u0026plusmn;\u0026thinsp;0.06 LogMAR, the corrected distance visual acuity (CDVA) was \u0026minus;\u0026thinsp;0.04\u0026thinsp;\u0026plusmn;\u0026thinsp;0.05 LogMAR and the manifest spherical equivalent refraction (MRSE) was 0.00\u0026thinsp;\u0026plusmn;\u0026thinsp;0.34 D. The Q-value increased from \u0026minus;\u0026thinsp;0.13\u0026thinsp;\u0026plusmn;\u0026thinsp;0.09 to 0.01\u0026thinsp;\u0026plusmn;\u0026thinsp;0.27, resulting in an oblate shift of 0.14\u0026thinsp;\u0026plusmn;\u0026thinsp;0.25 from the preoperative state. The preoperative SA was 0.24\u0026thinsp;\u0026plusmn;\u0026thinsp;0.06 \u0026micro;m, remaining stable at 0.24\u0026thinsp;\u0026plusmn;\u0026thinsp;0.13 \u0026micro;m postoperatively. The planned optical zone of 6.50 mm resulted in an achieved EOZ of 5.93\u0026thinsp;\u0026plusmn;\u0026thinsp;0.40 mm, a mean reduction of -0.57\u0026thinsp;\u0026plusmn;\u0026thinsp;0.40 mm. Myopia and compound myopic astigmatism correction with CLEAR therefore resulted in minimal positive shift in Q-value, limited EOZ reduction, and no overall induction of spherical aberration.\u003c/p\u003e","manuscriptTitle":"Effect of Q-Value Individualized CLEAR Kerato-refractive Lenticule Extraction Profile on Corneal Asphericity, Spherical Aberration, and Optical Zone Stability","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-05-07 06:28:55","doi":"10.21203/rs.3.rs-6404168/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2025-07-01T17:41:55+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-06-05T09:42:23+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"272096178640884244735166838738451881458","date":"2025-06-04T07:00:00+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"193402480066751599693951981486528658610","date":"2025-06-04T06:35:27+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-05-21T04:59:50+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"54984995040495916281054715832019622884","date":"2025-05-06T14:43:26+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-04-28T09:24:58+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-04-26T06:01:05+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"","date":"2025-04-16T14:30:02+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2025-04-16T03:10:16+00:00","index":"","fulltext":""},{"type":"submitted","content":"Scientific Reports","date":"2025-04-08T13:54:07+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"scientific-reports","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"scirep","sideBox":"Learn more about [Scientific Reports](http://www.nature.com/srep/)","snPcode":"","submissionUrl":"","title":"Scientific Reports","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Scientific Reports","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"2c1e34ce-1a2b-4fc1-84ae-d1ae4aab5413","owner":[],"postedDate":"May 7th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[{"id":47945885,"name":"Health sciences/Medical research/Study design/Clinical trials"},{"id":47945886,"name":"Health sciences/Medical research/Outcomes research"}],"tags":[],"updatedAt":"2025-08-25T16:30:07+00:00","versionOfRecord":{"articleIdentity":"rs-6404168","link":"https://doi.org/10.1038/s41598-025-16271-3","journal":{"identity":"scientific-reports","isVorOnly":false,"title":"Scientific Reports"},"publishedOn":"2025-08-19 16:12:52","publishedOnDateReadable":"August 19th, 2025"},"versionCreatedAt":"2025-05-07 06:28:55","video":"","vorDoi":"10.1038/s41598-025-16271-3","vorDoiUrl":"https://doi.org/10.1038/s41598-025-16271-3","workflowStages":[]},"version":"v1","identity":"rs-6404168","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-6404168","identity":"rs-6404168","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}