Outcome of Keratorefractive Surgery Among Myopes at Eye Foundation Hospital Group, Nigeria

Outcome of Keratorefractive Surgery Among Myopes at Eye Foundation Hospital Group, Nigeria | 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 Outcome of Keratorefractive Surgery Among Myopes at Eye Foundation Hospital Group, Nigeria Dr Agu Obiajulu, Dr Abimbola Ashaye This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-3225058/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 OBJECTIVES To determine the outcome of keratorefractive surgical procedures among myopes at Eye Foundation Hospital Group, Nigeria. MATERIALS & METHODS The study was a non-randomized prospective study with secondary intervention, conducted among consecutive consenting new patients diagnosed with myopia between − 1.0D to -10D at Eye foundation hospital group. Interviewer administered semi-structured questionnaires, in-depth interviews and focused group discussions were used to collect information on socio-demographic characteristics and post operative feed backs. Participants who had the surgery were closely observed to determine the safety, efficacy, predictability, and stability of the procedure. RESULTS Three hundred and two participants were enrolled into the study with mean age of 30.48 ± 8.44 years and an age range of 18 years to 57 years.Ten eyes of six participants underwent keratorefractive surgery constituting an uptake of 2.0%. The mean age of the participants who underwent keratorefractive surgeries was 28 ± 10.9 years and the range was 18 to 44 years. The mean spherical equivalent for those that had surgery were − 4.3 ± 2.7 D. Eighty percent and 100% of eyes were within ± 0.5 and 1.0 D of the intended correction, respectively and regarding efficacy at 3 months post-operation, the proportion of participants with post-operative uncorrected distance visual acuity of ≥ 6/9 and ≥ 6/6 were 100% and 70% respectively. Regarding safety at 3 months post-operation, 3 eyes (30%) showed no change in corrected distance visual acuity (CDVA), 6 eyes (60%) gained 1 line and 1 eye (10%) lost 1 line. No vision threatening complications were observed in any of the cases. CONCLUSION Good surgical outcome was observed amongst those that were treated and future studies on keratorefractive surgery with larger sample sizes to determine the long-term effects among Nigerians are advocated. Ophthalmology Safety efficacy stability predictability keratorefractive surgery myopia Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 INTRODUCTION Myopia (nearsightedness) is a refractive error, in which images of distant objects focus in front of the retina, when accommodation is relaxed. Myopia is categorized into two groups namely: low to moderate myopia (-0.50 D to -5.0 D of myopic spherical equivalent (SE) with or without astigmatism) and high myopia ( -6.0 D or more of myopic spherical equivalent with or without astigmatism) adopted as the World Health Organization (WHO) definition in 2015. 1 , 2 Myopia is the most common visually significant refractive error and a leading cause of vision impairment worldwide with its prevalence increasing globally . 3 The Nigeria National Blindness and Visual Impairment Survey (NNBVIS) reported the crude prevalence of myopia (-0.5D to -5.0D) and high myopia (-6.0 D or more) to be 16.2% and 2.1%, respectively. 4 Recent studies in Nigeria have shown a steady rise in the prevalence of myopia. 5 – 6 It has been predicted that, by the year 2050, high myopia will affect 9.8% of the global population. 7 The prevalence of myopia is reported to be highest in East Asia, where China, Japan, Republic of Korea and Singapore each have a prevalence of approximately 50%, but prevalence is lower in Australia, Europe and America. 2 Myopia and high myopia were estimated to affect 27% (1,893 million) and 2.8% (170 million) of the world population, respectively, in 2010, making myopia one of the leading causes of visual impairment and blindness worldwide, hence a major public health challenge. 2 This will place a greater burden on health services to provide spectacles as well as prevent and manage the conditions associated with high myopia. 2 People with high myopia are at increased risk of potentially blinding eye conditions such as myopic choroidal neovascular membrane (CNVM), myopic macular degeneration, retinal detachment, open-angle glaucoma and cataract, thereby making it a major public health challenge. 7 Until the end of the 20th century, spectacles and contact lenses were the principal methods recommended by ophthalmologists and optometrists for managing this global problem. The development of the excimer laser in 1983 opened up the world of keratorefractive surgery. 8 Keratorefractive surgeries encompass surgical procedures used to improve the refractive state of the eye and decrease or eliminate dependency on corrective lenses. These procedures are essentially aimed at modifying the refractive power of the eye by changing the corneal curvature using lasers. They include photorefractive keratectomy, laser assisted subepithelial keratectomy (LASEK), epithelial laser assisted in situ keratomileusis (Epi-LASIK), laser in situ keratomileusis (LASIK) and small incision lenticular extraction (SMILE). Other refractive surgeries include intra-corneal insertion of rings or gels or changing the lenticular power using phakic lenses in the anterior or posterior chamber or clear lens extraction as for high myopia. 9 The mechanism of keratorefractive surgery in correcting myopia is by decreasing the refractive power of the eye, thereby making the images of distant objects to focus on the retina so as to obtain a safe, predictable, stable and desired refractive state. Major innovations and breakthroughs have helped to make keratorefractive surgery safe, precise, predictable and stable, and improve not only the vision but the quality of life of millions of patients who have benefited from it. With the remarkable technological advancements achieved thus far, the popularity of refractive surgery will likely continue to increase. However, concerns about the outcome measures of keratorefractive surgery, such as efficacy, stability, and safety, persist in the general population. 8 This study was conducted to determine the outcome of keratorefractive surgery among myopes in a center that readily offers the services. METHODS This was a prospective descriptive cross-sectional study conducted at different locations of the Eye Foundation Hospital Group, Nigeria. This study was carried out following the guidelines as contained in the declaration of Helsinki and approval was obtained from the Ethics and Research Committee of the Lagos State University Teaching Hospital, Ikeja, Lagos, Nigeria. The participants were patients who came for eye consultations in the eye clinics of the health facility. Study design The criteria for inclusion of the participants in the study were new consenting adult patients age 18 years and above, diagnosed with any form of myopia. Written consent was obtained after the study had been explained to each participant. This study had both quantitative and qualitative components. The quantitative component was the prospective study while the qualitative component consists of both in-depth interview and focused group discussion (FGD). Each of the participants was interviewed using a pre-tested semi-structured questionnaire ( adapted from previous studies). 3 Interviewer administered semi-structured questionnaires, in-depth interviews and focused group discussions were used to collect information on socio-demographic characteristics and post operative feed backs. Participants who had the surgery were closely observed to determine the safety, efficacy, predictability, and stability of the procedure and also, the proportion of patients with post-operative uncorrected visual acuity of ≥ 6/9 and ≥ 6/6 were assessed after first day, first week, first month and third month post-operatively. Eligibility for Surgery Eligibility for surgery included manifest spherical equivalent of -1.00 D to -10 D, manifest cylinder of -1.00 D to -4.00 D, sufficient cornea thickness greater than 400 microns, estimated residual stromal thickness of at least 250 microns, absence of co-existing ocular pathologies like visually significant cataract, keratoconus, retinitis pigmentosa, retinal detachment, macula hole/scar, progressive cornea degenerations. Surgical Procedure (A). Small incision lenticular extraction (SMILE) The operation was performed with Visumax femtosecond laser platform (Carl Zeiss Meditec AG, Jena, Germany). Consent was taken and asepsis maintained. The spot distance was set at 3µm for lamellar cuts and 2µm for side cuts while the spot energy was set at 140 Nj. The minimum lenticule side cut thickness was set at 15µm, the lenticule side cut angle was set at 120 and optical zone at 6.5mm. Visumax femtosecond laser was used to create a refractive lenticule and small incision of less than 4mm in the intact cornea. The lenticule was dissected completely and extracted through the side cut with forceps. Target spherical correction was slight hypermetropia (+ 0.50 D) for 18–29 years, emmetropia for 30–36 years, slight myopia (-0.50 D) for 37–40 years and monovision strategy for participants over 40 years. Target astigmatism was emmetropia. Postoperatively, all eyes received topical dexamethazone and ciprofloxacin 2 hourly for 1 week and the frequency was steadily reduced thereafter. Artificial tears were prescribed at least for one month. (B). Laser-assisted in situ keratomileusis procedure (LASIK) Excimer laser (Carl Zeiss Mel 80 laser) was done under aseptic condition. Ablation and transition zone was set at 6mm and 1mm respectively. Flap was created using femtosecond laser after which the, stromal bed was reshaped using excimer laser. Target spherical correction was slight hypermetropia (+ 0.50 D) for 18–29 years, emmetropia for 30–36 years, slight myopia (-0.50 D) for 37–40 years and monovision strategy for participants over 40 years. Target astigmatism was emmetropia. Postoperatively, all eyes received topical dexamethazone and ciprofloxacin medications 2 hourly for 1 week and the frequency steadily reduced thereafter. Artificial tears were prescribed at least for one month. Definition of terms Myopia Myopia for keratorefractive procedure was defined as myopic spherical equivalent (SE) with or without astigmatism between − 1.0 D or more. 10 Low to moderate myopia (less than − 5.0 D of myopic spherical equivalent) and high myopia ( -5.0 D or more of myopic spherical equivalent). 1 , 2 Safety Safety of keratorefractive procedure was measured in 2 ways: the percentage of patients with postoperative loss of 2 or more lines of corrected distance visual acuity (CDVA) on the Snellen chart and the incidence of surgical complications. 8 Efficacy Efficacy of keratorefractive procedure was assessed by comparing the difference between the postoperative uncorrected visual acuity (UCVA) and the preoperative corrected distance visual acuity (CDVA). 11 Predictability Predictability was assessed by the mean difference between postoperative spherical equivalent (SE) and intended correction. 11 Stability Stability was assessed by the mean difference between postoperative spherical equivalent (SE) and intended correction over time. 11 Target induced astigmatism (TIA) Defined as the difference between the preoperative astigmatism and target astigmatism. 12 Surgically induced astigmatism (SIA) Defined as the difference between the preoperative cylinder and postoperative cylinder as the actual correction achieved. 12 Correction index (CI) Defined as the ratio of the SIA to the TIA. The CI is preferably 1; >1 shows overcorrection while < 1 shows undercorrection. Outcome measures: The outcome measures were assessed at 1 day, 1 week, 1 month and 3 months post-operatively. The primary outcome measure was to determine the proportion of patients with post-operative uncorrected visual acuity of ≥ 6/9 and ≥ 6/6 while the secondary outcome measure was to determine the safety, efficacy, predictability and stability of the procedure. Data analysis Data was analyzed using the IBM Statistical Package for Social Sciences (IBM-SPSS) version 26 (IBM Corp: Armonk, NY USA). Frequencies and proportions were used to summarize categorical variables while mean, mode and median were used for quantitative variables. Chi-square test was used to compare categorical variables and test of associations between them. Shapiro-wilk test was used to determine normality of quantitative variables. Student’s t-test and Wilcoxin sign ranked tests were used for comparison of continuous variables depending on normality. A p-value less than 0.05 was considered as statistically significant. Linear regression analysis was used to predict the value of the outcome variable from the independent variable and logistic regression was done for variables with significant association. The results are displayed using tables, pie charts, graph, scatter plots and bar charts. RESULTS Three hundred and two participants were enrolled into the study with mean age of 30.48 ± 8.44 years and an age range of 18 years to 57 years. Keratorefractive surgery was performed on 10 eyes of 6 participants constituting an uptake of 2.0%. They were all from the urban areas. Eight eyes (80%) of the participants underwent SMILE and two eyes (20%) of a participant underwent LASIK. The participant who opted for LASIK at the time of surgery was based on personal preference. Two eyes of the 6 participants had myopia >-10D, so were excluded. The mean age of the participants who underwent keratorefractive surgeries was 28 ± 10.9 years and the range was 18 to 44 years. Two (33.3%) participants were male while four (66.7%) were females. Their preoperative and 3 months postoperative visual acuity, refraction and corneal parameter are shown in Table 1 . The number of eyes at follow-up examination were 10 eyes at 1day, 9 eyes at 1 week, 7 eyes at 1 month, and 10 eyes at 3 months, post-operative. Table 1 Preoperative and 3 months postoperative visual acuity, refraction and corneal parameter Parameter Pre-operative Mean ± SD; range. N = 10 Post-operative Mean ± SD; range N = 10 p - value Keratometer (D) 43.1 ± 1.7; 41.6 to 45.9 39 ± 2.7; 34.4 to 41.1 0.002* Central Cornea Thickness (µm) 516 ± 17.7; 488 to 534 417 ± 26; 377 to 455 < 0.001* Uncorrected visual acuity (UCVA) 0.92 ± 0.25; 0.6 to 1.3 0.03 ± 0.14; -0.1 to 0.24 0.005* Corrected distance visual acuity (CDVA) 0.01 ± 0.03; 0.0 to 0.1 -0.03 ± 0.1; -0.1 to 0.2 0.206 Manifest spherical equivalent (D) -4.3 ± 2.7; -10.0 to -1.5 -0.28 ± 0.42; -1.0 to 0.0 < 0.001* Manifest cylinder (D) -0.58 ± 0.67; -1.5 to 0.0 -0.2 ± 0.35; -1.0 to 0.0 0.129 N= Total number of eyes examined Efficacy and Safety Regarding efficacy at 3 months post-operation, 70% and 100% of eyes had UCVA of 6/6 or better and 6/9 or better, respectively (Fig. 1 ). Four eyes (44.4%) showed no change in UCVA, 4 eyes (44.4%) gained 1 line, 1 eye (11.2%) lost 1 line and two lines loss was 0% (Fig. 2 ). Regarding safety at 3 months post-operation, 3 eyes (30%) showed no change in CDVA, 6 eyes (60%) gained 1 line and 1 eye (10%) lost 1 line (Fig. 3 ). Post-operative ocular symptoms Eight eyes (80%) had ocular symptoms immediate post-operative. The most frequent ocular complaints were eye pain (62.5%) and foreign body sensations (50.0%), while dry eyes, photophobia, blurred vision and tearing were 25% each. Complications Diffuse lamellar keratitis occurred in the 2 eyes (20%) of a patient during the first postoperative month. These eyes were monitored and there was resolution of the keratitis in one of the eyes. It however persisted in the other eye which necessitated an interface washout one week post-operation after which it gradually resolved. The eye lost one snellen line of CDVA at 3 months post-operative. Predictability and Stability Regarding the spherical diopter after keratorefractive surgery, the spherical refraction was almost fully corrected. There were strong correlations between the attempted spherical correction and the achieved spherical correction in the absolute value at 3 months postoperative (r = 0.978, p = < 0.001, Pearson rank correlation). Regarding the cylindrical refraction, the correction index was 0.65 ± 0.14, which shows undercorrection (Fig. 4 ). The absolute values of the surgical induced astigmatism (SIA) and target induced astigmatism (TIA) were strongly correlated at 3 months postoperative (r = 0.821, p = < 0.001, Pearson rank correlation). 90% of the eyes had astigmatism ≤ 0.5 D (Fig. 5 ). Figure 6 shows the changes over time in the subjective refraction. No significant change in refraction was seen from 1 day to 3 months postoperatively (2-way ANOVA,p = 0.186). Post-operative feedback from focused group discussion/in-depth interview Participant from focus group : ‘Am very satisfied with my treatment’ Participant from focus group : ‘Hahahahaha… I actually threw my spectacles away’ Participant from in-depth interview : ‘My vision now is far better than before...I told my friends about it and they are willing to come do theirs as well’ Participant from in-depth interview : ‘To be honest with you, am not satisfied. Though I can now see distance vision clearly but am having difficulty reading, which was not the case before this surgery’ DISCUSSION This study revealed that 100% as well as 70% of participants had UCVA of ≥ 6/9 and ≥ 6/6 respectively at three months post-operation. These findings were similar to the observations of Kazutaka et al, 13 who reported that 100% of eyes had UCVA of 20/20 and 20/40 respectively but slightly different to the observations of Chuck et al 10 who reported that 70% and 92% of participants had UCVA of 20/20 and 20/40 at 12 or more months post-operation following PRK. The similarity seen between this study and kazutaka et al, 13 may be due to the fact that both studies included myopic spherical equivalent less than or equal to -10 D, unlike the report by Chuck et al 10 which included myopic spherical equivalent greater than − 10 D. Very high levels of myopia (greater than − 10 D) is a risk factor for under correction, high regression rates, low efficacy and loss in best corrected visual acuity following keratorefractive surgery. 11 Furthermore, the longer follow up period as well as difference in the type of keratorefractive surgery may contribute to the disparity between this study and the observations of Chuck et al. 10 This study also revealed that 100% of eyes treated were within ± 1.00D of attempted correction. Loss of CDVA of two lines or more in this study was 0% which was comparable with the findings of Alper et al. 11 Regarding cylindrical refraction, this study showed under correction, similar to the findings by Zhang et al 12 and Chan et al 14 , but correction index of 0.65 ± 0.14 from this study was lower than that reported by Zhang et al (0.97 ± 0.3) 12 and Chan et al (0.98 ± 0.08) 14 . This can be attributed to the fewer number of participants in this study compared to theirs. A larger number of participants will be needed to have a true reflection on the state of cylindrical refractive correction. In terms of stability, no significant refractive regression was found from day 1 to 3 months after keratorefractive surgery in this study. This is similar to the findings of Kazutaka et al. 13 However, the long-term refractive stability of keratorefractive surgery cannot be concluded at this time, since the follow up period was for 3 months. Alper et al. 11 found statistically significant trend of regression in their study on outcome of SMILE in high myopia, with achieved spherical equivalent of -0.26 D, -0.33 D, and − 0.43 D at 1,3, and 5 years, respectively. This may be due to high regression rates associated with high myopia as compared with the low to moderate myopia. In this study, two eyes (20%) developed postoperative diffuse lamellar keratitis and one eye required a surgical intervention. At 3 months post-operation, the eye that had further surgical intervention lost one snellen line due to astigmatism but visual acuity was 6/9. Alper et al 11 had no sight threatening complications while Kazutaka et al 13 had suction loss in 3 eyes (1.2%), subconjunctival hemorrhage in 7 eyes (2.8%), transient interface haze and diffuse lamellar keratitis in 23 eyes (9.1%) and 2 eyes (0.8%) respectively, during their first postoperative month. They were monitored without additional surgical intervention, and gradually resolved. No keratectasia, epithelial ingrowth, or any other severe complications were observed in this study. Keratorefractive surgeries (SMILE and LASIK) was safe in the six participants that underwent the procedure as 60% of participants gained 1 snellen line of CDVA and 30% of participants had no change in snellen line of CDVA with absence of severe complications. Similarly, studies with longer follow-up and larger samples have also shown good safety parameters. 11 , 13 The limitations in this study were short follow up period, small sample size for those that had keratorefractive surgery, non-randomized nature of the study. However, the results of this study could serve as a foundation for future studies on keratorefractive surgery in Nigeria as it provided information that could be useful for patients’ counseling, health planning, improving surgical uptake and advocacy as well as a better understanding of patients’ disposition to the procedure. CONCLUSION Good surgical outcome was observed amongst those that were treated, 100% as well as 70% of participants had UCVA of ≥ 6/9 and ≥ 6/6 respectively at three months post-operation. Future studies on keratorefractive surgery with larger sample sizes to determine the long-term effects among Nigerians are advocated. DECLARATION Competing interests: The authors declare no competing interests. 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Visual and refractive outcomes of small-incision lenticule extraction in high myopia: 5-Year Results. Hindawi Journal of Ophthalmology. Volume 2018, Article ID 5893126, 6 pages. Jiamei Z, Yan W, Wenjing W, Lulu X, Xiaojing L, Rui D. Vector analysis of low to moderate astigmatism with small incision lenticule extraction (SMILE): results of a 1 year follow up: BMC Ophthalmology 2015; 15:8. Kazutaka K, Masahide T, tomoaki N, Takashi K, Ikuko T, Maro K. A multicenter study on early outcomes of small-incision lenticule extraction for myopia. Scientific Reports 2019; 9:4067. https://doi.org/10.1038/s41598-019-40805-1. Chan T, Yan W, Alex L, Jiamei Z, Marco C, Vishal J et al. Vector analysis of high astigmatism correction using small incision lenticule extraction and laser in situ keratomileusis: J Cataract Refract Surg 2018; 4:38. 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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-3225058","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":223265095,"identity":"9e0f5ac5-3d8d-40a9-bb18-07bfc2945af5","order_by":0,"name":"Dr Agu 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excluded.\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"Picture5.png","url":"https://assets-eu.researchsquare.com/files/rs-3225058/v1/943f60a7e58aedb5376584bd.png"},{"id":41087653,"identity":"816576ba-1975-400d-bddc-3008c991df68","added_by":"auto","created_at":"2023-08-04 17:12:24","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":18651,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eSafety showing changes in corrected distance visual acuity (CDVA) 3 months after keratorefractive surgery\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"Picture6.png","url":"https://assets-eu.researchsquare.com/files/rs-3225058/v1/32a843ee39643e438f7aff40.png"},{"id":41087656,"identity":"2cfecaeb-6924-4511-8b53-8677acc38d4b","added_by":"auto","created_at":"2023-08-04 17:12:24","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":29266,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003ePredictability of spherical refraction showing scatter plot of the attempted versus the achieved manifest spherical equivalent correction after 3 months keratorefractive surgery\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"Picture7.png","url":"https://assets-eu.researchsquare.com/files/rs-3225058/v1/46664646e230f7e1d8519155.png"},{"id":41088384,"identity":"86654a16-859d-45e1-8e28-960105d3108c","added_by":"auto","created_at":"2023-08-04 17:20:24","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":26775,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003ePredictability of cylindrical refraction showing scatter plot of the target induced astigmatism versus the surgically induced astigmatism after 3 months keratorefractive surgery\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"Picture8.png","url":"https://assets-eu.researchsquare.com/files/rs-3225058/v1/d88f8ec7949df209b1fea51f.png"},{"id":41087655,"identity":"97f61990-4765-456b-848d-2f12f92dab66","added_by":"auto","created_at":"2023-08-04 17:12:24","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":36972,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eStability of spherical equivalent refraction after keratorefractive surgery\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"Picture9.png","url":"https://assets-eu.researchsquare.com/files/rs-3225058/v1/1f508e09d740173d320dba9e.png"}],"financialInterests":"","formattedTitle":"\u003cp\u003e\u003cstrong\u003eOutcome of Keratorefractive Surgery Among Myopes at Eye Foundation Hospital Group, Nigeria\u003c/strong\u003e\u003c/p\u003e","fulltext":[{"header":"INTRODUCTION","content":"\u003cp\u003eMyopia (nearsightedness) is a refractive error, in which images of distant objects focus in front of the retina, when accommodation is relaxed. Myopia is categorized into two groups namely: low to moderate myopia (-0.50 D to -5.0 D of myopic spherical equivalent (SE) with or without astigmatism) and high myopia ( -6.0 D or more of myopic spherical equivalent with or without astigmatism) adopted as the World Health Organization (WHO) definition in 2015.\u003csup\u003e\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e,\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e\u003c/sup\u003e Myopia is the most common visually significant refractive error and a leading cause of vision impairment worldwide with its prevalence increasing globally .\u003csup\u003e\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e\u003c/sup\u003e\u003c/p\u003e \u003cp\u003eThe Nigeria National Blindness and Visual Impairment Survey (NNBVIS) reported the crude prevalence of myopia (-0.5D to -5.0D) and high myopia (-6.0 D or more) to be 16.2% and 2.1%, respectively.\u003csup\u003e\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e\u003c/sup\u003e Recent studies in Nigeria have shown a steady rise in the prevalence of myopia.\u003csup\u003e\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e\u003c/sup\u003e It has been predicted that, by the year 2050, high myopia will affect 9.8% of the global population.\u003csup\u003e\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e\u003c/sup\u003e The prevalence of myopia is reported to be highest in East Asia, where China, Japan, Republic of Korea and Singapore each have a prevalence of approximately 50%, but prevalence is lower in Australia, Europe and America.\u003csup\u003e\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e\u003c/sup\u003e\u003c/p\u003e \u003cp\u003eMyopia and high myopia were estimated to affect 27% (1,893\u0026nbsp;million) and 2.8% (170\u0026nbsp;million) of the world population, respectively, in 2010, making myopia one of the leading causes of visual impairment and blindness worldwide, hence a major public health challenge.\u003csup\u003e\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e\u003c/sup\u003e This will place a greater burden on health services to provide spectacles as well as prevent and manage the conditions associated with high myopia.\u003csup\u003e\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e\u003c/sup\u003e People with high myopia are at increased risk of potentially blinding eye conditions such as myopic choroidal neovascular membrane (CNVM), myopic macular degeneration, retinal detachment, open-angle glaucoma and cataract, thereby making it a major public health challenge.\u003csup\u003e\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e\u003c/sup\u003e\u003c/p\u003e \u003cp\u003eUntil the end of the 20th century, spectacles and contact lenses were the principal methods recommended by ophthalmologists and optometrists for managing this global problem. The development of the excimer laser in 1983 opened up the world of keratorefractive surgery.\u003csup\u003e\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e\u003c/sup\u003e Keratorefractive surgeries encompass surgical procedures used to improve the refractive state of the eye and decrease or eliminate dependency on corrective lenses. These procedures are essentially aimed at modifying the refractive power of the eye by changing the corneal curvature using lasers. They include photorefractive keratectomy, laser assisted subepithelial keratectomy (LASEK), epithelial laser assisted in situ keratomileusis (Epi-LASIK), laser in situ keratomileusis (LASIK) and small incision lenticular extraction (SMILE). Other refractive surgeries include intra-corneal insertion of rings or gels or changing the lenticular power using phakic lenses in the anterior or posterior chamber or clear lens extraction as for high myopia.\u003csup\u003e\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e\u003c/sup\u003e The mechanism of keratorefractive surgery in correcting myopia is by decreasing the refractive power of the eye, thereby making the images of distant objects to focus on the retina so as to obtain a safe, predictable, stable and desired refractive state. Major innovations and breakthroughs have helped to make keratorefractive surgery safe, precise, predictable and stable, and improve not only the vision but the quality of life of millions of patients who have benefited from it. With the remarkable technological advancements achieved thus far, the popularity of refractive surgery will likely continue to increase. However, concerns about the outcome measures of keratorefractive surgery, such as efficacy, stability, and safety, persist in the general population.\u003csup\u003e\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e\u003c/sup\u003e This study was conducted to determine the outcome of keratorefractive surgery among myopes in a center that readily offers the services.\u003c/p\u003e"},{"header":"METHODS","content":"\u003cp\u003eThis was a prospective descriptive cross-sectional study conducted at different locations of the Eye Foundation Hospital Group, Nigeria. This study was carried out following the guidelines as contained in the declaration of Helsinki and approval was obtained from the Ethics and Research Committee of the Lagos State University Teaching Hospital, Ikeja, Lagos, Nigeria. The participants were patients who came for eye consultations in the eye clinics of the health facility.\u003c/p\u003e\n\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\n\u003ch2\u003eStudy design\u003c/h2\u003e\n\u003cp\u003eThe criteria for inclusion of the participants in the study were new consenting adult patients age 18 years and above, diagnosed with any form of myopia. Written consent was obtained after the study had been explained to each participant. This study had both quantitative and qualitative components. The quantitative component was the prospective study while the qualitative component consists of both in-depth interview and focused group discussion (FGD).\u003c/p\u003e\n\u003cp\u003eEach of the participants was interviewed using a pre-tested semi-structured questionnaire ( adapted from previous studies).\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e3\u003c/span\u003e\u003c/sup\u003e Interviewer administered semi-structured questionnaires, in-depth interviews and focused group discussions were used to collect information on socio-demographic characteristics and post operative feed backs. Participants who had the surgery were closely observed to determine the safety, efficacy, predictability, and stability of the procedure and also, the proportion of patients with post-operative uncorrected visual acuity of \u0026ge;\u0026thinsp;6/9 and \u0026ge;\u0026thinsp;6/6 were assessed after first day, first week, first month and third month post-operatively.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec4\" class=\"Section2\"\u003e\n\u003ch2\u003eEligibility for Surgery\u003c/h2\u003e\n\u003cp\u003eEligibility for surgery included manifest spherical equivalent of -1.00 D to -10 D, manifest cylinder of -1.00 D to -4.00 D, sufficient cornea thickness greater than 400 microns, estimated residual stromal thickness of at least 250 microns, absence of co-existing ocular pathologies like visually significant cataract, keratoconus, retinitis pigmentosa, retinal detachment, macula hole/scar, progressive cornea degenerations.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec5\" class=\"Section2\"\u003e\n\u003ch2\u003eSurgical Procedure\u003c/h2\u003e\n\u003cdiv id=\"Sec6\" class=\"Section3\"\u003e\n\u003ch2\u003e(A). Small incision lenticular extraction (SMILE)\u003c/h2\u003e\n\u003cp\u003eThe operation was performed with Visumax femtosecond laser platform (Carl Zeiss Meditec AG, Jena, Germany). Consent was taken and asepsis maintained. The spot distance was set at 3\u0026micro;m for lamellar cuts and 2\u0026micro;m for side cuts while the spot energy was set at 140 Nj. The minimum lenticule side cut thickness was set at 15\u0026micro;m, the lenticule side cut angle was set at 120 and optical zone at 6.5mm. Visumax femtosecond laser was used to create a refractive lenticule and small incision of less than 4mm in the intact cornea. The lenticule was dissected completely and extracted through the side cut with forceps. Target spherical correction was slight hypermetropia (+\u0026thinsp;0.50 D) for 18\u0026ndash;29 years, emmetropia for 30\u0026ndash;36 years, slight myopia (-0.50 D) for 37\u0026ndash;40 years and monovision strategy for participants over 40 years. Target astigmatism was emmetropia. Postoperatively, all eyes received topical dexamethazone and ciprofloxacin 2 hourly for 1 week and the frequency was steadily reduced thereafter. Artificial tears were prescribed at least for one month.\u003c/p\u003e\n\u003c/div\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec7\" class=\"Section2\"\u003e\n\u003ch2\u003e(B). Laser-assisted in situ keratomileusis procedure (LASIK)\u003c/h2\u003e\n\u003cp\u003eExcimer laser (Carl Zeiss Mel 80 laser) was done under aseptic condition. Ablation and transition zone was set at 6mm and 1mm respectively. Flap was created using femtosecond laser after which the, stromal bed was reshaped using excimer laser. Target spherical correction was slight hypermetropia (+\u0026thinsp;0.50 D) for 18\u0026ndash;29 years, emmetropia for 30\u0026ndash;36 years, slight myopia (-0.50 D) for 37\u0026ndash;40 years and monovision strategy for participants over 40 years. Target astigmatism was emmetropia. Postoperatively, all eyes received topical dexamethazone and ciprofloxacin medications 2 hourly for 1 week and the frequency steadily reduced thereafter. Artificial tears were prescribed at least for one month.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec8\" class=\"Section2\"\u003e\n\u003ch2\u003eDefinition of terms\u003c/h2\u003e\n\u003cp\u003e\u003cstrong\u003eMyopia\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eMyopia for keratorefractive procedure was defined as myopic spherical equivalent (SE) with or without astigmatism between \u0026minus;\u0026thinsp;1.0 D or more.\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e10\u003c/span\u003e\u003c/sup\u003e Low to moderate myopia (less than \u0026minus;\u0026thinsp;5.0 D of myopic spherical equivalent) and high myopia ( -5.0 D or more of myopic spherical equivalent).\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e1\u003c/span\u003e,\u003cspan class=\"CitationRef\"\u003e2\u003c/span\u003e\u003c/sup\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eSafety\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eSafety of keratorefractive procedure was measured in 2 ways: the percentage of patients with postoperative loss of 2 or more lines of corrected distance visual acuity (CDVA) on the Snellen chart and the incidence of surgical complications.\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e8\u003c/span\u003e\u003c/sup\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eEfficacy\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eEfficacy of keratorefractive procedure was assessed by comparing the difference between the postoperative uncorrected visual acuity (UCVA) and the preoperative corrected distance visual acuity (CDVA).\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e11\u003c/span\u003e\u003c/sup\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003ePredictability\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003ePredictability was assessed by the mean difference between postoperative spherical equivalent (SE) and intended correction.\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e11\u003c/span\u003e\u003c/sup\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eStability\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eStability was assessed by the mean difference between postoperative spherical equivalent (SE) and intended correction over time.\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e11\u003c/span\u003e\u003c/sup\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTarget induced astigmatism (TIA)\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eDefined as the difference between the preoperative astigmatism and target astigmatism.\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e12\u003c/span\u003e\u003c/sup\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eSurgically induced astigmatism (SIA)\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eDefined as the difference between the preoperative cylinder and postoperative cylinder as the actual correction achieved.\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e12\u003c/span\u003e\u003c/sup\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCorrection index (CI)\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eDefined as the ratio of the SIA to the TIA. The CI is preferably 1; \u0026gt;1 shows overcorrection while\u0026thinsp;\u0026lt;\u0026thinsp;1 shows undercorrection.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec9\" class=\"Section2\"\u003e\n\u003ch2\u003eOutcome measures:\u003c/h2\u003e\n\u003cp\u003eThe outcome measures were assessed at 1 day, 1 week, 1 month and 3 months post-operatively. The primary outcome measure was to determine the proportion of patients with post-operative uncorrected visual acuity of \u0026ge;\u0026thinsp;6/9 and \u0026ge;\u0026thinsp;6/6 while the secondary outcome measure was to determine the safety, efficacy, predictability and stability of the procedure.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec10\" class=\"Section2\"\u003e\n\u003ch2\u003eData analysis\u003c/h2\u003e\n\u003cp\u003eData was analyzed using the IBM Statistical Package for Social Sciences (IBM-SPSS) version 26 (IBM Corp: Armonk, NY USA). Frequencies and proportions were used to summarize categorical variables while mean, mode and median were used for quantitative variables. Chi-square test was used to compare categorical variables and test of associations between them. Shapiro-wilk test was used to determine normality of quantitative variables. Student\u0026rsquo;s t-test and Wilcoxin sign ranked tests were used for comparison of continuous variables depending on normality. A p-value less than 0.05 was considered as statistically significant. Linear regression analysis was used to predict the value of the outcome variable from the independent variable and logistic regression was done for variables with significant association. The results are displayed using tables, pie charts, graph, scatter plots and bar charts.\u003c/p\u003e\n\u003c/div\u003e"},{"header":"RESULTS","content":"\u003cp\u003eThree hundred and two participants were enrolled into the study with mean age of 30.48\u0026thinsp;\u0026plusmn;\u0026thinsp;8.44 years and an age range of 18 years to 57 years. Keratorefractive surgery was performed on 10 eyes of 6 participants constituting an uptake of 2.0%. They were all from the urban areas. Eight eyes (80%) of the participants underwent SMILE and two eyes (20%) of a participant underwent LASIK. The participant who opted for LASIK at the time of surgery was based on personal preference. Two eyes of the 6 participants had myopia \u0026gt;-10D, so were excluded. The mean age of the participants who underwent keratorefractive surgeries was 28\u0026thinsp;\u0026plusmn;\u0026thinsp;10.9 years and the range was 18 to 44 years. Two (33.3%) participants were male while four (66.7%) were females. Their preoperative and 3 months postoperative visual acuity, refraction and corneal parameter are shown in Table\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e. The number of eyes at follow-up examination were 10 eyes at 1day, 9 eyes at 1 week, 7 eyes at 1 month, and 10 eyes at 3 months, post-operative.\u003c/p\u003e\n\u003cdiv class=\"gridtable\"\u003e\n\u003ctable id=\"Tab1\" border=\"1\"\u003e\u003ccaption\u003e\n\u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e\n\u003cdiv class=\"CaptionContent\"\u003e\n\u003cp\u003ePreoperative and 3 months postoperative visual acuity, refraction and corneal parameter\u003c/p\u003e\n\u003c/div\u003e\n\u003c/caption\u003e\n\u003cthead\u003e\n\u003ctr\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eParameter\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003ePre-operative\u003c/p\u003e\n\u003cp\u003eMean\u0026thinsp;\u0026plusmn;\u0026thinsp;SD; range.\u003c/p\u003e\n\u003cp\u003eN\u0026thinsp;=\u0026thinsp;10\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003ePost-operative\u003c/p\u003e\n\u003cp\u003eMean\u0026thinsp;\u0026plusmn;\u0026thinsp;SD; range\u003c/p\u003e\n\u003cp\u003eN\u0026thinsp;=\u0026thinsp;10\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003ep\u003cem\u003e-\u003c/em\u003evalue\u003c/p\u003e\n\u003c/th\u003e\n\u003c/tr\u003e\n\u003c/thead\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eKeratometer (D)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e43.1\u0026thinsp;\u0026plusmn;\u0026thinsp;1.7; 41.6 to 45.9\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e39\u0026thinsp;\u0026plusmn;\u0026thinsp;2.7; 34.4 to 41.1\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e0.002*\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eCentral Cornea Thickness (\u0026micro;m)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e516\u0026thinsp;\u0026plusmn;\u0026thinsp;17.7; 488 to 534\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e417\u0026thinsp;\u0026plusmn;\u0026thinsp;26; 377 to 455\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e\u0026lt; 0.001*\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eUncorrected visual acuity (UCVA)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e0.92\u0026thinsp;\u0026plusmn;\u0026thinsp;0.25; 0.6 to 1.3\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e0.03\u0026thinsp;\u0026plusmn;\u0026thinsp;0.14; -0.1 to 0.24\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e0.005*\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eCorrected distance visual acuity (CDVA)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e0.01\u0026thinsp;\u0026plusmn;\u0026thinsp;0.03; 0.0 to 0.1\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e-0.03\u0026thinsp;\u0026plusmn;\u0026thinsp;0.1; -0.1 to 0.2\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e0.206\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eManifest spherical equivalent (D)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e-4.3\u0026thinsp;\u0026plusmn;\u0026thinsp;2.7; -10.0 to -1.5\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e-0.28\u0026thinsp;\u0026plusmn;\u0026thinsp;0.42; -1.0 to 0.0\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e\u0026lt; 0.001*\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eManifest cylinder (D)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e-0.58\u0026thinsp;\u0026plusmn;\u0026thinsp;0.67; -1.5 to 0.0\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e-0.2\u0026thinsp;\u0026plusmn;\u0026thinsp;0.35; -1.0 to 0.0\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e0.129\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003e\u003cstrong\u003eN= Total number of eyes examined\u003c/strong\u003e\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec12\" class=\"Section2\"\u003e\n\u003cdiv id=\"Sec13\" class=\"Section3\"\u003e\n\u003ch2\u003eEfficacy and Safety\u003c/h2\u003e\n\u003cp\u003eRegarding efficacy at 3 months post-operation, 70% and 100% of eyes had UCVA of 6/6 or better and 6/9 or better, respectively (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e). Four eyes (44.4%) showed no change in UCVA, 4 eyes (44.4%) gained 1 line, 1 eye (11.2%) lost 1 line and two lines loss was 0% (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003e). Regarding safety at 3 months post-operation, 3 eyes (30%) showed no change in CDVA, 6 eyes (60%) gained 1 line and 1 eye (10%) lost 1 line (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003e).\u003c/p\u003e\n\u003c/div\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec14\" class=\"Section2\"\u003e\n\u003ch2\u003ePost-operative ocular symptoms\u003c/h2\u003e\n\u003cp\u003eEight eyes (80%) had ocular symptoms immediate post-operative. The most frequent ocular complaints were eye pain (62.5%) and foreign body sensations (50.0%), while dry eyes, photophobia, blurred vision and tearing were 25% each.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec15\" class=\"Section2\"\u003e\n\u003ch2\u003eComplications\u003c/h2\u003e\n\u003cp\u003eDiffuse lamellar keratitis occurred in the 2 eyes (20%) of a patient during the first postoperative month. These eyes were monitored and there was resolution of the keratitis in one of the eyes. It however persisted in the other eye which necessitated an interface washout one week post-operation after which it gradually resolved. The eye lost one snellen line of CDVA at 3 months post-operative.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec16\" class=\"Section2\"\u003e\n\u003ch2\u003ePredictability and Stability\u003c/h2\u003e\n\u003cp\u003eRegarding the spherical diopter after keratorefractive surgery, the spherical refraction was almost fully corrected. There were strong correlations between the attempted spherical correction and the achieved spherical correction in the absolute value at 3 months postoperative (r\u0026thinsp;=\u0026thinsp;0.978, p\u0026thinsp;=\u0026thinsp;\u0026lt;\u0026thinsp;0.001, Pearson rank correlation). Regarding the cylindrical refraction, the correction index was 0.65\u0026thinsp;\u0026plusmn;\u0026thinsp;0.14, which shows undercorrection (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003e). The absolute values of the surgical induced astigmatism (SIA) and target induced astigmatism (TIA) were strongly correlated at 3 months postoperative (r\u0026thinsp;=\u0026thinsp;0.821, p\u0026thinsp;=\u0026thinsp;\u0026lt;\u0026thinsp;0.001, Pearson rank correlation). 90% of the eyes had astigmatism\u0026thinsp;\u0026le;\u0026thinsp;0.5 D (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e5\u003c/span\u003e). Figure\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e6\u003c/span\u003e shows the changes over time in the subjective refraction. No significant change in refraction was seen from 1 day to 3 months postoperatively (2-way ANOVA,p\u0026thinsp;=\u0026thinsp;0.186).\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec17\" class=\"Section2\"\u003e\n\u003ch2\u003ePost-operative feedback from focused group discussion/in-depth interview\u003c/h2\u003e\n\u003cp\u003eParticipant from focus group : \u0026lsquo;Am very satisfied with my treatment\u0026rsquo;\u003c/p\u003e\n\u003cp\u003eParticipant from focus group : \u0026lsquo;Hahahahaha\u0026hellip; I actually threw my spectacles away\u0026rsquo;\u003c/p\u003e\n\u003cp\u003eParticipant from in-depth interview : \u0026lsquo;My vision now is far better than before...I told my friends about it and they are willing to come do theirs as well\u0026rsquo;\u003c/p\u003e\n\u003cp\u003eParticipant from in-depth interview : \u0026lsquo;To be honest with you, am not satisfied. Though I can now see distance vision clearly but am having difficulty reading, which was not the case before this surgery\u0026rsquo;\u003c/p\u003e\n\u003c/div\u003e"},{"header":"DISCUSSION","content":"\u003cp\u003eThis study revealed that 100% as well as 70% of participants had UCVA of \u0026ge;\u0026thinsp;6/9 and \u0026ge;\u0026thinsp;6/6 respectively at three months post-operation. These findings were similar to the observations of Kazutaka et al,\u003csup\u003e\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e\u003c/sup\u003e who reported that 100% of eyes had UCVA of 20/20 and 20/40 respectively but slightly different to the observations of Chuck et al \u003csup\u003e\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e\u003c/sup\u003e who reported that 70% and 92% of participants had UCVA of 20/20 and 20/40 at 12 or more months post-operation following PRK. The similarity seen between this study and kazutaka et al,\u003csup\u003e\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e\u003c/sup\u003e may be due to the fact that both studies included myopic spherical equivalent less than or equal to -10 D, unlike the report by Chuck et al \u003csup\u003e\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e\u003c/sup\u003e which included myopic spherical equivalent greater than \u0026minus;\u0026thinsp;10 D. Very high levels of myopia (greater than \u0026minus;\u0026thinsp;10 D) is a risk factor for under correction, high regression rates, low efficacy and loss in best corrected visual acuity following keratorefractive surgery.\u003csup\u003e\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e\u003c/sup\u003e Furthermore, the longer follow up period as well as difference in the type of keratorefractive surgery may contribute to the disparity between this study and the observations of Chuck et al.\u003csup\u003e\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e\u003c/sup\u003e This study also revealed that 100% of eyes treated were within \u0026plusmn;\u0026thinsp;1.00D of attempted correction.\u003c/p\u003e \u003cp\u003eLoss of CDVA of two lines or more in this study was 0% which was comparable with the findings of Alper et al.\u003csup\u003e\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e\u003c/sup\u003e Regarding cylindrical refraction, this study showed under correction, similar to the findings by Zhang et al\u003csup\u003e\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e\u003c/sup\u003e and Chan et al\u003csup\u003e\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e\u003c/sup\u003e, but correction index of 0.65\u0026thinsp;\u0026plusmn;\u0026thinsp;0.14 from this study was lower than that reported by Zhang et al (0.97\u0026thinsp;\u0026plusmn;\u0026thinsp;0.3)\u003csup\u003e12\u003c/sup\u003e and Chan et al (0.98\u0026thinsp;\u0026plusmn;\u0026thinsp;0.08)\u003csup\u003e14\u003c/sup\u003e. This can be attributed to the fewer number of participants in this study compared to theirs. A larger number of participants will be needed to have a true reflection on the state of cylindrical refractive correction.\u003c/p\u003e \u003cp\u003eIn terms of stability, no significant refractive regression was found from day 1 to 3 months after keratorefractive surgery in this study. This is similar to the findings of Kazutaka et al.\u003csup\u003e\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e\u003c/sup\u003e However, the long-term refractive stability of keratorefractive surgery cannot be concluded at this time, since the follow up period was for 3 months. Alper et al.\u003csup\u003e\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e\u003c/sup\u003e found statistically significant trend of regression in their study on outcome of SMILE in high myopia, with achieved spherical equivalent of -0.26 D, -0.33 D, and \u0026minus;\u0026thinsp;0.43 D at 1,3, and 5 years, respectively. This may be due to high regression rates associated with high myopia as compared with the low to moderate myopia.\u003c/p\u003e \u003cp\u003eIn this study, two eyes (20%) developed postoperative diffuse lamellar keratitis and one eye required a surgical intervention. At 3 months post-operation, the eye that had further surgical intervention lost one snellen line due to astigmatism but visual acuity was 6/9. Alper et al\u003csup\u003e\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e\u003c/sup\u003e had no sight threatening complications while Kazutaka et al\u003csup\u003e\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e\u003c/sup\u003e had suction loss in 3 eyes (1.2%), subconjunctival hemorrhage in 7 eyes (2.8%), transient interface haze and diffuse lamellar keratitis in 23 eyes (9.1%) and 2 eyes (0.8%) respectively, during their first postoperative month. They were monitored without additional surgical intervention, and gradually resolved. No keratectasia, epithelial ingrowth, or any other severe complications were observed in this study. Keratorefractive surgeries (SMILE and LASIK) was safe in the six participants that underwent the procedure as 60% of participants gained 1 snellen line of CDVA and 30% of participants had no change in snellen line of CDVA with absence of severe complications. Similarly, studies with longer follow-up and larger samples have also shown good safety parameters.\u003csup\u003e\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e,\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e\u003c/sup\u003e\u003c/p\u003e \u003cp\u003eThe limitations in this study were short follow up period, small sample size for those that had keratorefractive surgery, non-randomized nature of the study. However, the results of this study could serve as a foundation for future studies on keratorefractive surgery in Nigeria as it provided information that could be useful for patients\u0026rsquo; counseling, health planning, improving surgical uptake and advocacy as well as a better understanding of patients\u0026rsquo; disposition to the procedure.\u003c/p\u003e"},{"header":"CONCLUSION","content":"\u003cp\u003eGood surgical outcome was observed amongst those that were treated, 100% as well as 70% of participants had UCVA of \u0026ge;\u0026thinsp;6/9 and \u0026ge;\u0026thinsp;6/6 respectively at three months post-operation. Future studies on keratorefractive surgery with larger sample sizes to determine the long-term effects among Nigerians are advocated.\u003c/p\u003e"},{"header":"DECLARATION","content":"\u003cp\u003eCompeting interests: The authors declare no competing interests.\u003c/p\u003e"},{"header":"REFERENCES","content":"\u003col\u003e\n\u003cli\u003eThe impact of myopia and high myopia: report of the Joint World Health Organization\u0026ndash;Brien Holden Vision Institute Global Scientific Meeting on Myopia, University of New South Wales, Sydney, Australia, 16-18 March 2015: 5.\u003c/li\u003e\n\u003cli\u003eHolden BA, Fricke TR, Wilson DA, Jong M, Naidoo KS, Sankaridurg P et al. Global Prevalence of Myopia and High Myopia and Temporal Trends from 2000 through 2050. Ophthalmology 2016;123(5):1036-42.\u003c/li\u003e\n\u003cli\u003ePan CW, Ramamurthy D, Saw SM. Worldwide prevalence and risk factors for myopia. Ophthalmic Physiology and Optics. 2012;32(1):3-16.\u003c/li\u003e\n\u003cli\u003eEzelum C, Razavi H, Sivasubramaniam S. Refractive error in Nigerian adults: prevalence, type, and spectacle coverage. Invest Ophthalmol Vis Sci 2011;52 (8):5449 5456. doi: 10.1167/iovs.10-6770\u003c/li\u003e\n\u003cli\u003eAbraham EG, Megbelayin EO. Pattern of Refractive Errors Among Ophthalmic Outpatients of University of Uyo Teaching Hospital, Uyo, Nigeria. Nigerian Journal of Ophthalmology,Jul-Dec 2015,Vol 23:Issue 2.p. 39-43\u003c/li\u003e\n\u003cli\u003eAjayi IA, Omotoye OJ, Omotoso-Olagoke O. Profile of refractive error in Ekiti, south western Nigeria. Afr Vision Eye Health. 2018;77(1), a415. https://doi.org/ 10.4102/aveh.v77i1.415\u003c/li\u003e\n\u003cli\u003eDolgin E. The myopia boom. Nature. 2015;519(7543):276-8.\u003c/li\u003e\n\u003cli\u003eEng K. Ang, Terry Couper, Mohamed Dirani, Rasik B. Vajpayee, Paul N. Baird. Outcomes of laser refractive surgery for myopia. Journal of Cataract \u0026amp; Refractive Surgery 2009;35(5):921-933\u003c/li\u003e\n\u003cli\u003eDieudonne K, Wa K. Advances in Eye Surgery.Refractive surgery for myopia.11:216 -217.http://dx.doi.org/10.5772/62106\u003c/li\u003e\n\u003cli\u003eChuck RS, Jacobs DS, Lee JK, Afshari NA, Vitale S, Shen TT et al. American academy of ophthalmology preferred practice pattern refractive management/intervention panel. Refractive errors \u0026amp; refractive surgery preferred practice pattern\u0026reg;. Ophthalmology. 2018;125(1):23-42. doi: 10.1016/j.ophtha.2017.10.003.\u003c/li\u003e\n\u003cli\u003eAlper A, I˙hsan \u0026Ccedil;, Beril TA, Dilek Y, Yusuf Y, Bur\u0026ccedil;in KY. Visual and refractive outcomes of small-incision lenticule extraction in high myopia: 5-Year Results. Hindawi Journal of Ophthalmology. Volume 2018, Article ID 5893126, 6 pages.\u003c/li\u003e\n\u003cli\u003eJiamei Z, Yan W, Wenjing W, Lulu X, Xiaojing L, Rui D. Vector analysis of low to moderate astigmatism with small incision lenticule extraction (SMILE): results of a 1 year follow up: BMC Ophthalmology 2015; 15:8.\u003c/li\u003e\n\u003cli\u003eKazutaka K, Masahide T, tomoaki N, Takashi K, Ikuko T, Maro K. A multicenter study on early outcomes of small-incision lenticule extraction for myopia. Scientific Reports 2019; 9:4067. https://doi.org/10.1038/s41598-019-40805-1.\u003c/li\u003e\n\u003cli\u003eChan T, Yan W, Alex L, Jiamei Z, Marco C, Vishal J et al. Vector analysis of high astigmatism correction using small incision lenticule extraction and laser in situ keratomileusis: J Cataract Refract Surg 2018; 4:38.\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":true,"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":"Safety, efficacy, stability, predictability, keratorefractive surgery, myopia","lastPublishedDoi":"10.21203/rs.3.rs-3225058/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-3225058/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003ch2\u003eOBJECTIVES\u003c/h2\u003e \u003cp\u003eTo determine the outcome of keratorefractive surgical procedures among myopes at Eye Foundation Hospital Group, Nigeria.\u003c/p\u003e\u003ch2\u003eMATERIALS \u0026amp; METHODS\u003c/h2\u003e \u003cp\u003e The study was a non-randomized prospective study with secondary intervention, conducted among consecutive consenting new patients diagnosed with myopia between \u0026minus;\u0026thinsp;1.0D to -10D at Eye foundation hospital group. Interviewer administered semi-structured questionnaires, in-depth interviews and focused group discussions were used to collect information on socio-demographic characteristics and post operative feed backs. Participants who had the surgery were closely observed to determine the safety, efficacy, predictability, and stability of the procedure.\u003c/p\u003e\u003ch2\u003eRESULTS\u003c/h2\u003e \u003cp\u003eThree hundred and two participants were enrolled into the study with mean age of 30.48\u0026thinsp;\u0026plusmn;\u0026thinsp;8.44 years and an age range of 18 years to 57 years.Ten eyes of six participants underwent keratorefractive surgery constituting an uptake of 2.0%. The mean age of the participants who underwent keratorefractive surgeries was 28\u0026thinsp;\u0026plusmn;\u0026thinsp;10.9 years and the range was 18 to 44 years. The mean spherical equivalent for those that had surgery were \u0026minus;\u0026thinsp;4.3\u0026thinsp;\u0026plusmn;\u0026thinsp;2.7 D. Eighty percent and 100% of eyes were within \u0026plusmn;\u0026thinsp;0.5 and 1.0 D of the intended correction, respectively and regarding efficacy at 3 months post-operation, the proportion of participants with post-operative uncorrected distance visual acuity of \u0026ge;\u0026thinsp;6/9 and \u0026ge;\u0026thinsp;6/6 were 100% and 70% respectively. Regarding safety at 3 months post-operation, 3 eyes (30%) showed no change in corrected distance visual acuity (CDVA), 6 eyes (60%) gained 1 line and 1 eye (10%) lost 1 line. No vision threatening complications were observed in any of the cases.\u003c/p\u003e\u003ch2\u003eCONCLUSION\u003c/h2\u003e \u003cp\u003eGood surgical outcome was observed amongst those that were treated and future studies on keratorefractive surgery with larger sample sizes to determine the long-term effects among Nigerians are advocated.\u003c/p\u003e","manuscriptTitle":"Outcome of Keratorefractive Surgery Among Myopes at Eye Foundation Hospital Group, Nigeria","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2023-08-04 17:12:19","doi":"10.21203/rs.3.rs-3225058/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":"a8364263-69a2-4ee7-9482-fde4e7fc7c55","owner":[],"postedDate":"August 4th, 2023","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[{"id":23799811,"name":"Ophthalmology"}],"tags":[],"updatedAt":"2023-08-09T03:40:20+00:00","versionOfRecord":[],"versionCreatedAt":"2023-08-04 17:12:19","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-3225058","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-3225058","identity":"rs-3225058","version":["v1"]},"buildId":"cBFmMYwuxLRRLfASyISRj","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}