Spectacle Correction Research Articles

Prevalence and pattern of refractive error and visual impairment among schoolchildren: the Lhasa childhood eye study

BackgroundEarly and effective ocular screening may help to eliminate treatable eye disorders. The Lhasa Childhood Eye Study (LCES) revealed the particular prevalence of refractive error and visual impairment in grade one schoolchildren (starting age of 6 years old) in Lhasa.MethodsThis is a cross-sectional part of school-based cohort study. One thousand nine hundred forty-three children were enrolled (median age, 6.78 years, range, 5.89 to 10.32). Each child underwent general and ocular examinations, including logarithm of the minimum angle of resolution (logMAR) visual acuity, cycloplegic autorefraction, and slit-lamp biomicroscopy evaluation. Multivariate and correlation analyses were performed to evaluate the association between refractive error with gender and ethnics.ResultsThe prevalence of visual impairment (logMAR visual acuity ≥0.3 in the better-seeing eye) of uncorrected, presenting and best-corrected visual acuity (BCVA) was 12.2, 11.7 and 2.7%, respectively. Refractive error presented in 177 (78.0%) out of 227 children with bilateral visual impairment. Myopia (spherical equivalent refractor [SER] ≤ − 0.50 diopter [D] in either eye) was present in 4.7% children when measured after cycloplegic autorefraction. Hyperopia (SER ≥ + 2.00 D) affected 12.1% children. Hyperopia was significantly associated with female gender (P<0.001). Astigmatism (cylinder value ≤ − 0.75 D) was present in 44.8% children. In multivariate regression and correlation analysis, SER had no significant difference between ethnic groups.ConclusionThe Lhasa Childhood Eye Study is the first school-based cohort study to reveal the prevalence and pattern of refractive error and visual impairment in Lhasa. Effective strategies such as corrective spectacles should be considered to alleviate treatable visual impairment.

Unilateral Traumatic Posterior Corneal Ectasia: Clinical Manifestations, Findings of Advanced Imaging, and Long-term Follow-up

PURPOSE: To describe a case of unilateral isolated traumatic posterior corneal ectasia characterized by advanced multi-modal diagnostic tests. METHODS: Case report and literature review. RESULTS: Following blunt trauma to the left eye, a 34-year-old woman presented with persistently blurry vision. Central corneal thickness was 300 µm, compared to 519 µm in the right eye. Scheimpflug tomography revealed significant corneal thinning in a defined inferotemporal region with corresponding elevation of the posterior corneal surface. Posterior corneal ectasia was confirmed with anterior segment optical coherence tomography. Wavefront aberrometry demonstrated increased higher order aberrations in the affected eye. Vision remained stable during 4.5 years of follow-up with a final visual acuity of 20/50 maintained with spectacle correction only. CONCLUSIONS: A unique case of unilateral post-traumatic posterior corneal ectasia was presented. The multi-modal imaging provided a detailed characterization of the structural characteristics of the cornea, guided management, and allowed for differentiation from other corneal pathologies at an early stage. [ Journal of Refractive Surgery Case Reports . 2021;1(2):e31–e35.]

Epithelium-off corneal cross-linking surgery compared with standard care in 10- to 16-year-olds with progressive keratoconus: the KERALINK RCT

Background Keratoconus is a disease of the cornea affecting vision that is usually first diagnosed in the first three decades. The abnormality of corneal shape and thickness tends to progress until the patient reaches approximately 30 years of age. Epithelium-off corneal cross-linking is a procedure that has been demonstrated to be effective in randomised trials in adults and observational studies in young patients. Objectives The KERALINK trial examined the efficacy and safety of epithelium-off corneal cross-linking, compared with standard care by spectacle or contact lens correction, for stabilisation of progressive keratoconus. Design In this observer-masked, randomised, controlled, parallel-group superiority trial, 60 participants aged 10–16 years with progressive keratoconus were randomised; 58 participants completed the study. Progression was defined as a 1.5 D increase in corneal power measured by maximum or mean power (K2) in the steepest corneal meridian in the study eye, measured by corneal tomography. Setting Referral clinics in four UK hospitals. Interventions Participants were randomised to corneal cross-linking plus standard care or standard care alone, with spectacle or contact lens correction as necessary for vision, and were monitored for 18 months. Main outcome measures The primary outcome was K2 in the study eye as a measure of the steepness of the cornea at 18 months post randomisation. Secondary outcomes included keratoconus progression, visual acuity, keratoconus apex corneal thickness and quality of life. Results Of 60 participants, 30 were randomised to the corneal cross-linking and standard-care groups. Of these, 30 patients in the corneal cross-linking group and 28 patients in the standard-care group were analysed. The mean (standard deviation) K2 in the study eye at 18 months post randomisation was 49.7 D (3.8 D) in the corneal cross-linking group and 53.4 D (5.8 D) in the standard-care group. The adjusted mean difference in K2 in the study eye was –3.0 D (95% confidence interval –4.93 D to –1.08 D; p = 0.002), favouring corneal cross-linking. Uncorrected and corrected differences in logMAR vision at 18 months were better in eyes receiving corneal cross-linking: –0.31 (95% confidence interval –0.50 to –0.11; p = 0.002) and –0.30 (95% confidence interval –0.48 to –0.11; p = 0.002). Keratoconus progression in the study eye occurred in two patients (7%) randomised to corneal cross-linking compared with 12 (43%) patients randomised to standard care. The unadjusted odds ratio suggests that, on average, patients in the corneal cross-linking group had 90% (odds ratio 0.1, 95% confidence interval 0.02 to 0.48; p = 0.004) lower odds of experiencing progression than those receiving standard care. Quality-of-life outcomes were similar in both groups. No adverse events were attributable to corneal cross-linking. Limitations Measurements of K2 in those eyes with the most significant progression were in some cases indicated as suspect by corneal topography device software. Conclusions Corneal cross-linking arrests progression of keratoconus in the great majority of young patients. These data support a consideration of a change in practice, such that corneal cross-linking could be considered as first-line treatment in progressive disease. If the arrest of keratoconus progression induced by corneal cross-linking is sustained in longer follow-up, there may be particular benefit in avoiding the later requirement for contact lens wear or corneal transplantation. However, keratoconus does not continue to progress in all patients receiving standard care. For future work, the most important questions to be answered are whether or not (1) the arrest of keratoconus progression induced by corneal cross-linking is maintained in the long term and (2) the proportion of those receiving standard care who show significant progression increases with time. Trial registration Current Controlled Trials ISRCTN17303768 and EudraCT 2016-001460-11. Funding This project was funded by the Efficacy and Mechanism Evaluation (EME) programme, a Medical Research Council (MRC) and National Institute for Health Research (NIHR) partnership. This will be published in full in Efficacy and Mechanism Evaluation; Vol. 8, No. 15. See the NIHR Journals Library website for further project information. The trial sponsor is University College London. This research was otherwise supported in part by the NIHR Moorfields Biomedical Research Centre and the NIHR Moorfields Clinical Research Facility, London, United Kingdom.

Successful Combination Therapy for Amblyopia Secondary to Micro-Esotropia And Anisometropia

Background: Micro-esotropia is a small-angle esodeviation typically less than nine prism diopters. Patients with this ocular condition often develop amblyopia due to the presence of a constant unilateral strabismus and an anisometropic refractive error in the deviated eye. Current treatment methods for strabismic and refractive amblyopia include spectacle correction, patching, and vision therapy (VT). Case Summary: A 9-year-old Asian female presented with a constant left primary micro-esotropia with unsteady eccentric fixation, contributing to mild amblyopia and frequent suppression in the left eye. She also had a hyperopic anisometropic refractive error. Combination treatment of in-office VT with short-term patching therapy (two hours per day) was administered, with the goal of improving her binocularity, fixation, and visual acuity. Conclusions: Amblyopia results from binocular dysfunction, therefore monocular patching therapy alone will not improve the underlying issue. VT is necessary to actively treat binocularity and subsequently improve visual acuity, while short-term patching can be used in combination to effectively target monocular accommodation and fixation.

Cause of amblyopia in adult patients: a cross-sectional study

Background: Amblyopia has been defined as a decrease of visual acuity for which no causes can be detected by the physical examination of the eye, caused by vision deprivation or abnormal binocular interaction. This study aims to determine the cause of amblyopia in adult patients at HAHC hospital South Delhi.Methods: This is a cross-sectional study conducted over a period from January 2018 till March 2018 among the patients in HAHC hospital. A comprehensive eye examination was used to analyse the visual condition.Results: Amblyopia was diagnosed in 42 participants, with age-and gender-adjusted prevalence of 3.2%. Of these, 1.9% were unilateral cases, and 1.3% were bilateral cases. A major cause of amblyopia in this population was a refractive error, hence using spectacle correction and vision therapy for its initial management.Conclusions: This study has provided causes of amblyopia in an adult population. Amblyopia is a frequent cause of lifelong unilateral visual impairment.

Modeling refractive correction strategies in keratoconus.

This work intends to determine the optimal refractive spectacle and scleral lens corrections for keratoconus patients using the visual Strehl (VSX) visual image quality metric and the SyntEyes models with the synthetic biometry of 20 normal eyes and 20 keratoconic eyes. These included the corneal tomography and intraocular biometry. A series of virtual spherocylindrical spectacle and scleral lens corrections spanning the entire phoropter range were separately applied to each eye, followed by ray tracing to determine the residual wavefront aberrations and identify the correction with the highest possible VSX (named a “focus”). To speed up calculations, a smart scanning algorithm was used, consisting of three consecutive scans over increasingly finer dioptric grids. In the dioptric space, the VSX pattern for normal eyes considered over the correction range for either spectacle or scleral lens corrections resembled an hourglass with one distinct focus and a quick drop in VSX away from that focus. For 18 of the 20 keratoconic eyes, the spectacle-corrected VSX pattern resembled a shell that in 9 of the 20 cases showed two foci separated by a large dioptric distance (13.3 ± 4.9 diopters). In keratoconic eyes, scleral lenses also produced hourglass patterns, but with a VSX lower than in normal eyes. The hourglass pattern in dioptric space shows how, in normal eyes, the refracting process automatically funnels practitioners toward the optimal correction. The shell patterns in keratoconus, however, present far more complexity and, possibly, multiple foci. Depending on the starting point, refracting procedures may lead to a local maximum rather than the optimal correction.

Five-year results of refractive outcomes and vision-related quality of life after SMILE for the correction of high myopia.

To evaluate the long-term visual, refractive outcomes and vision-related quality of life after small incision lenticule extraction (SMILE) for the correction of high myopia. Thirty patients (60 eyes) with high myopia who underwent SMILE more than 5y were selected as the SMILE group. Another 30 high myopia patients (60 eyes) who had worn corrective spectacles for more than 5y were selected as the control group. In SMILE group, the postoperative follow-up time were 3, 6mo, 1 and 5y. Uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), spherical equivalent (SE), and ocular axial length (AL) were analyzed. The Chinese version of the National Eye Institute Visual Function Questionnaire-25 (CHI-NEI-VFQ-25) was used to evaluate the vision-related quality of life in the SMILE group and the control group. In SMILE group, the mean preoperative SE was -7.29±0.87 D (range -6.00 to -9.125 D). At 5-year follow up, the efficacy index and safety index of SMILE were 1.09±0.18 and 1.19±0.12, respectively. Five years postoperatively, 44 eyes (73%) obtained a visual acuity of 20/20 or better. There were no eyes with CDVA loss of one or more Snellen lines. Forty-nine eyes (82%) and 57 eyes (95%) were within ±0.50 and ±1.00 D of attempted correction at 5-year follow-up, respectively. Forty-eight eyes (80%) had astigmatism <0.50 D at 5-year follow-up. The postoperative mean SE values at 3, 6mo, 1, and 5y were 0.11±0.44, 0.07±0.45, -0.02±0.41, and -0.15±0.46 D, respectively. No significant change was observed in the ocular AL from before operation to 5y postoperatively (26.08±0.96 mm vs 26.01±0.94 mm, P=0.068). Compared to the control group, the SMILE group showed a significantly higher total score on the CHI-NEI-VFQ-25 (90.14 vs 81.43, P<0.001). In the present study, in a long-term follow-up we demonstrate that correcting high myopia with SMILE is safe, effective, and predictable. Vision-related quality of life after SMILE is better in the SMILE group than in the control group who wore corrective spectacles.

How Contact Lenses Have Influenced Research Developments in Optics and Vision Science

Initially, contact lenses were developed as the only viable option to provide improved vision for patients suffering from conditions which distortedthe corneal surface in an irregular fashion, rendering spectacle correction an unsatisfactory option. Developments in materials, fitting methods andmanufacturing technologies soon made contact lenses an appealing option for all spectacle wearers, particularly with the development of toricand multifocal lens options. Although the optical challenges of contact lenses appeared to be relatively straightforward in their early years, thedevelopment of improved in-vivo diagnostic and in-vitro metrology instrumentation led to a significantly greater understanding of the nature of theoptical errors (e.g. higher order wavefront aberrations) of the eye and contact lenses and the interactions between them when worn. The featuresof contact lenses having extremely steep curvatures and being aligned closely to the eye’s visual axis in all positions of gaze provide both uniquechallenges and opportunities for improving the visual performance of both physiological and pathological eyes, and have guided the efforts ofsignificant vison science research in more recent times.

Factors affecting non-compliance to spectacle wear in children aged six years and below with refractive errors: A hospital based cross-sectional study in India

Uncorrected refractive errors (RE) are the most common cause of preventable visual Impairment (VI) in children, which if not treated in time can lead to amblyopia. VI in early childhood interferes with their overall development affecting their future opportunities in life. Spectacles remain the most popular and effective method for correction of RE. Children unlike adults, often don’t understand the need for wearing spectacles, thus prescribing spectacles in children becomes difficult. Aim of this study was to find out proportion of spectacle wear non-compliance in children aged six years and below and identify factors associated with it. The study was conducted among 115 children aged six years and below with refractive errors who were prescribed spectacle correction. Children were selected using simple random sampling. Multivariate logistic regression was used to identify independent factors associated with spectacle wear non-compliance. Proportion of spectacle wear non-compliance was 53.04%. Children with spectacle wear non-compliance were more likely to: belong to age of two to four years (AOR = 4.3; 95%CI: 1.3-14.3); have mother with up-to primary school education (AOR = 3.7; 95%CI: 1.2-11.7); have anisometropia (AOR = 11.1; 95%CI: 3.4-36.7). Statistically significant association was observed between spectacle wear non-compliance and child’s age, mother’s education, anisometropia, astigmatism, manifest squint, intolerance to glasses, glasses lost, glasses broken, concerned teasing and cost issues. Children less than four years of age; with anisometropia and those whose mothers had up-to primary school education were more likely to be non-compliant to spectacle wear.

Changes in corneal curvature and visual acuity in North Indian adults after pterygium excision with modified sutureless, glueless limbal-conjunctival autograft.

Purpose:To identify the exact time point during after following pterygium excision with a modified technique of sutureless, glueless limbal-conjunctival autograft, when stabilization of the change in corneal curvature is achieved; correlate size of pterygium with uncorrected visual acuity and astigmatism at baseline, and assess changes in these parameters postoperatively over time.Methods:This prospective study longitudinally assessed 30 eyes of 30 north Indian adults with primary pterygium encroaching upon ≥1 mm of the cornea pre- and postoperatively at 1 week and then monthly for 4 months, recording uncorrected (UCVA) and best-corrected logMAR visual acuity, astigmatism and keratometry. Results were analyzed using ANOVA, Mauchly’s test of sphericity with Greenhouse–Geisser correction, and post-hoc test using Bonferroni correction. Pearson’s correlation coefficient r > 0.5 was considered clinically significant, and P < 0.05 statistically significant.Results:Pterygium size was well correlated with pre-operative astigmatism (r = 0.867, P < 0.001) and pre-operative UCVA (r = 0.856, P < 0.001). There was mean improvement of 0.43 logMAR units of visual acuity (P < 0.00001), a mean increase of 0.79D of keratometric value for the flatter meridian (P < 0.00001) and a mean reduction of 2.00D of astigmatism (P < 0.00001). At 2-month follow-up, the keratometric value for the flatter meridian approached the final keratometric reading at 4 months such that the difference was not significant (t = 1.185, P = 0.245). There were no significant complications or recurrence during the follow-up period.Conclusion:Pterygium excision with modified autograft reduced corneal astigmatism and improved visual acuity comparable to classical technique. Alteration in corneal curvature stabilizes 2 months after surgery, when spectacle correction can be given to patients.

Retinal image size in pseudophakia.

Approaches are developed to determine relative retinal magnifications in anisometropic patients undergoing cataract surgery; these can be used to balance between full spectacle corrections with equal intraocular lens (IOL) powers and a pure IOL power correction. The analysis started from the original and pseudophakic Navarro eye models, where in the latter case an IOL replaced the natural lens. A third model was a simplified Navarro-IOL model with a single surface cornea and a thin lens. These models were manipulated by altering vitreous length, corneal power and lens position. Retinal image sizes were determined for both full IOL corrections and full spectacle corrections by raytracing and approximate equations. Relative magnification (RM) was determined as the ratio of retinal image size of an eye to that of the appropriate standard eye. For raytracing and full IOL correction, vitreous length led to RM change of 5%/mm, while for corneal power and IOL position this was -0.4%/D and 1.4%/mm, respectively. For raytracing and spectacle correction, effects were 0%/D (vitreous depth), -1.6%/D (corneal power) and +1.0%/mm (IOL position). For full IOL correction, the approximate RM calculations were highly accurate. For spectacle correction, the approximate RM calculations were exact for vitreous length changes, reasonably accurate for corneal power changes but very inaccurate for changes in anterior chamber depth. Relative magnification approximations may be useful to assess the risk of aniseikonia in anisometropic patients targeted for postoperative emmetropia. Some of these patients would be corrected best by a combination of spectacles and IOLs.

What are patients' beliefs about, and experiences of, adaptation to glasses and how does this affect their wearing habits?

It is well known that some patients experience difficulties adapting to new glasses. However, little is known about what patients themselves understand of the adaptation process, and how this influences their attitudes and the decisions they make when adapting to a new pair of glasses. Nor is it understood whether these factors affect their wearing habits. We conducted four focus groups. Participants were 22glasses wearers (mean±SD age 43±14years, range 21-71years) who reported they: (1) wore spectacle correction for distance vision (single vision, bifocal or progressive lenses); (2) had struggled to get used to a new pair of glasses and (3) sometimes chose not to wear their distance correction. Focus groups were audio recorded, transcribed verbatim and analysed thematically. We identified three themes. Trust is about how participants' trust in their optometrist and themselves influences the likelihood of them adapting successfully to new glasses. Conflict describes how the advice patients have received about adapting to glasses can conflict with what they have experienced and how this conflict influences their expectations. Part of Me explores how participants' experiences and feelings about their glasses are important to adaptation and this includes physical, visual, emotional and behavioural aspects. The traditional optometric perspective of adaptation to glasses is much narrower than that held by patients, and significantly underestimates the physical, behavioural and emotional adaptation that patients must go through in order to feel fully comfortable wearing their glasses. Patients should receive significantly more information about adaptation, including symptoms that may be experienced and why these happen, practical tips to aid adaptation, and when and how to raise concerns. Patients should also receive information about the day-to-day effects of blur adaptation to avoid them not wearing their glasses, including for vision-critical tasks such as driving.

Barriers and Perception Towards Spectacle Wear among a Student Population of University of Buraimi, Oman.

ObjectivesThe study aimed to evaluate the barriers and perceptions towards spectacle wear among the student population of the University of Buraimi, Oman.MethodsA descriptive, questionnaire-based and cross-sectional study was conducted between December 2017 and May 2018. Ophthalmic examination and a standard spectacle prescription protocol were used to identify those with inappropriate spectacle coverage. A self-designed and expert validated English-language questionnaire was utilised. A chi-square test was used to assess the association between the participants’ types of perceptions and sociodemographic and refractive error-related profiles.ResultsIn total, 275 students participated in the study (response rate: 17.19%) and 170 (61.8%) were having inappropriate spectacle correction. Only 26% of them used spectacles since the majority (73.5%) had never had their eyes examined before this study. Most perceived spectacle wear positively (53.5%), followed by some having negative (36.5%) or neutral (10.0%) perceptions. Those from a health science background including Nursing and Optometry had a higher positive perception towards spectacle wear than others (P = 0.012). The difference in the perception scores between myopic and hypermetropic refractive error groups was statistically insignificant (P = 0.882).ConclusionThe majority of the participants had had inappropriate vision corrections with spectacles and not undergone any prior ocular examinations. Few wore spectacles; however, these were inappropriate given their current refractive status. The reasons for spectacle non-wear were that either new spectacles had been ordered or spectacles were lost or broken. It is recommended that the school eye health initiative be extended to the university level. A holistic eye-health promotional approach toward integrating students, teachers and parents into this initiative can improve spectacle wear within the studied population.

Glasses vs observation for moderate bilateral astigmatism in 1- to 7-year-olds

Although uncorrected astigmatism in young children is associated with the development of amblyopia, guidelines for spectacle correction are based primarily on provider surveys.[1-2] This study compares visual outcomes in children with moderate bilateral astigmatism treated with glasses to those who were merely observed.

Glasses Versus Observation for Moderate Bilateral Astigmatism in 1- to

To compare visual outcomes in children with moderate bilateral astigmatism treated with glasses with those who were merely observed. Retrospective case series. The medical records of all children 1 to <7 years of age who were diagnosed with moderate bilateral astigmatism (+1.25 to +3.25 diopters [D]) at a single institution over a 12-year period were retrospectively reviewed. Children with anisometropia ≥1.00 D, hyperopia ≥+3.00 D, myopia ≥-3.00D, amblyopia, or strabismus at diagnosis were excluded. Observation or full spectacle correction of astigmatism was at the provider's discretion. Kaplan-Meier rates of developing amblyopia and strabismus were assessed over a minimum follow-up of 18 months. Eighty-five (6.9%) of 1235 subjects met the inclusion criteria; 58 (68.2%) were prescribed glasses while 27 (31.8%) were observed. The groups differed by mean age at diagnosis (3.56 ± 1.42 years for observed vs 4.31 ± 1.36 years for glasses [P=.03]) and mean amount of astigmatism (1.73 ± 0.43 D for observed vs 2.00 ± 0.51 D for glasses [P=.02]). By 4 years of follow-up, the Kaplan-Meier rate of developing amblyopia was 8.3% (95% confidence interval [CI] 0%-19.4%) in the observed group and 10.3% (95% CI 1.5%-19.1%) in the glasses group [P=.74] while strabismus was 7.1% (95% CI 0%-20.6%) among those observed and 7.1% (95% CI 0.4%-13.8%) of those prescribed glasses [P=.60]. Rates of amblyopia and strabismus were similar and modest in this cohort of children with moderate bilateral astigmatism treated with glasses vs observation. These results suggest that prescribing glasses for these children may be no better than observation in preventingthe development of amblyopia or strabismus.

The prevalence and causes of visual impairment in Dariyah, a rural community in Saudi Arabia

Background: Visual impairment is disproportionately distributed between rural and urban dwellers. Rural dwellers have limited access to the eye care services that are available in urban cities. Aim: The aim of this study was to determine the prevalence and causes of visual impairment in Dariyah, a rural community in the Qassim region, Saudi Arabia. Setting: This research comprised a population-based assessment of the vision and visual status of the inhabitants of Dariyah community. Methods: A cross-sectional descriptive study was conducted amongst the inhabitants of the community of Dariyah. A comprehensive eye examination consisting of visual acuity, ocular health examination, objective and subjective refraction was performed. The examinations were conducted by registered ophthalmologists and optometrists from the Qassim University. Vision impairments were categorised according to the International Classification of Diseases (ICD), Section 9D90, ‘Vision impairment including blindness’ (2018). Results: In all, 68 (24.5%) participants had vision impairment (using the better-seeing eye), with refractive errors being the main cause of vision impairment. Other causes of vision impairment included cataract (20, 7.2%), trichiasis (5, 1.8%) and glaucoma (2, 0.7%). Refractive errors were present in 193 (69.7%), with astigmatism being the commonest refractive error. About 60% of those with refractive errors presented without spectacles for correction, and 20% reported that they had never had an eye examination. Refractive errors could not be determined in 19 (6.9%) of the subjects because of conditions such as matured cataract and other ocular abnormalities. Conclusion: Uncorrected refractive error was found to be the leading cause of vision impairment in this rural community in Saudi Arabia.

The Castrop formula for calculation of toric intraocular lenses

PurposeTo explain the concept behind the Castrop toric lens (tIOL) power calculation formula and demonstrate its application in clinical examples.MethodsThe Castrop vergence formula is based on a pseudophakic model eye with four refractive surfaces and three formula constants. All four surfaces (spectacle correction, corneal front and back surface, and toric lens implant) are expressed as spherocylindrical vergences. With tomographic data for the corneal front and back surface, these data are considered to define the thick lens model for the cornea exactly. With front surface data only, the back surface is defined from the front surface and a fixed ratio of radii and corneal thickness as preset. Spectacle correction can be predicted with an inverse calculation.ResultsThree clinical examples are presented to show the applicability of this calculation concept. In the 1st example, we derived the tIOL power for a spherocylindrical target refraction and corneal tomography data of corneal front and back surface. In the 2nd example, we calculated the tIOL power with keratometric data from corneal front surface measurements, and considered a surgically induced astigmatism and a correction for the corneal back surface astigmatism. In the 3rd example, we predicted the spherocylindrical power of spectacle refraction after implantation of any toric lens with an inverse calculation.ConclusionsThe Castrop formula for toric lenses is a generalization of the Castrop formula based on spherocylindrical vergences. The application in clinical studies is needed to prove the potential of this new concept.

Causes for Rejection of Keratorefractive Surgery in a Central Indian Population.

AimTo identify the reasons for refusing refractive surgery in patients visiting for spectacle-free vision.MethodologyMedical records of 296 patients who presented for keratorefractive surgery (KRS) from June 2017 to April 2020 at a tertiary eye care center in central India (Government Medical College and Hospital, Nagpur, Maharashtra, India) were reviewed. Demographic details of all the patients and parameters obtained during workup of a case presented for KRSs were captured in an Excel® sheet and analyzed statistically.ResultsOf the 296 patients who presented for KRS during the study period, 86 (29.1%) patients were denied KRS. The mean pachymetry in the right eye was 505 μm ± 10 μm (range 520-485 μm) and 502 μm ± 7 μm (511-490 μm) in the left eye. Suboptimal corneal thickness (n = 28, 32.6%) was the most common reason for rejection. Other reasons for not recommending the procedure were high myopia (n = 20, 23.3%), spectacle not stable (n = 16, 18.6%), and keratoconus (n = 11, 12.8%). Collagen vascular diseases (n = 3, 3.5%) and anxiety about the procedure (n = 2, 2.3%) were causes unrelated to the procedure. No correlation was observed between corneal thickness and degree of myopia (r = 0.014, p = 0.66).ConclusionPatients presenting for KRS exhibit various problems. Meticulous preoperative evaluation is most important for long-term visual outcome. Suboptimal corneal thickness, high myopia, unstable spectacle correction, and keratoconus were the common reasons for not performing KRS in the study population.

Knowledge and Attitude of Refractive Error Among Public High School Students in Gondar City.

IntroductionRefractive error (RE) is the main cause of visual impairment and blindness in the world. Lack of knowledge and unfavorable attitude of refractive error can have long-term consequences and dramatic effects in children and adults, such as loss of educational and employment opportunities, loss of economic gain for individuals, families, and societies, and impaired quality of life.AimThe aim of this study was to assess the level of knowledge and attitude of refractive error among public high school students in Gondar city, Northwest Ethiopia.MethodsA school-based cross-sectional study was conducted on 390 public high school students. Those participants were selected by applying a systematic random sampling technique with an interval of 4. Data were collected using a pre-tested structured questionnaire through face-to-face interviews. The collected data were entered into Epi Info version 7.0 and exported into SPSS version 20 for analysis. Results were described using tables and text.ResultsA total of 390 study participants were included in this study with a 92.4% response rate. The overall proportion of good knowledge and a favorable attitude towards a refractive error were 53.8% and 52.1%, respectively. From the study participants, 38.7%, 41.7%, and 64.1% did not know the definition, the risk factors, and the symptoms of refractive error, respectively. Moreover, about 31.3% of the participants believed that wearing spectacle could damage their eyes, whereas 44.1% of the participants agreed with the need for spectacle correction for young people with RE.ConclusionThe proportion of good knowledge and a favorable attitude towards refractive error among public high school students were fair. We recommended that eye care practitioners be committed to increasing the knowledge and attitude of students towards refractive error through eye health education to reduce visual impairment due to refractive error.

Epidemiology of Myopia in Children of the Russian Federation and Analysis of Its Control Methods

The increasing prevalence of myopia is observed all over the world, and Russia is no exception. In this regard, obtaining new data on its epidemiology among children and assessing methods of its control in real clinical practice are highly topical matters.Purpose. The purpose of this work was to assess the current issues of the epidemiology and treatment of progressive myopia in children in various regions of the Russian Federation.Materials and methods. We conducted a prospective multicenter epidemiological observational questionnaire study. This study involved 106 doctors from 53 regions of Russia and 2931 parents of myopic children.Results. 50% of the surveyed doctors noted that the manifestation of myopia is diagnosed in children aged 10–12 years, while 43% noted the same in children aged 7–9 years. According to 74.5% of doctors, the degree of the newly diagnosed myopia ranges from –1.25 to –3.00 diopters, 25.5% of doctors reported that it is below –1.0 diopters. The majority of doctors (73.6%) assess accommodation in myopic children, considering it one of the progression factors. 52.9% of ophthalmologists prescribe optical correction in cases when monocular distance visual acuity amounts to 0.6 (decimal scale) or lower values, while 29.2%, 16% and 1.9% of the surveyed ophthalmologists prescribe optical correction in cases when monocular distance visual acuity amounts to 0.7, 0.8 and 0.9 respectively.The following optical methods for juvenile myopia control are recommended by the doctors: orthokeratology contact lenses (53.8%), spectacles for full correction (51.9%), peripheral defocus-inducing (bifocal) soft contact lenses (18.9%), while 4.7% of the surveyed doctors utilized other methods of myopia control, which were not indicated in the questionnaire.Conclusion. In most cases, manifestation of myopia is diagnosed in children aged 7–12 years. Its degree ranges from –1.25 to –3.0 diopters, which indicates its late diagnosis; optical correction is prescribed mainly in cases when monocular distance visual acuity is 0.6 or lower; most ophthalmologists assess accommodation in myopic children, considering it a progression factor. As methods of myopia control, doctors utilize optical correction, device-assisted therapy and pharmacological treatment of accommodative disorders, while parents prefer methods that require minimum time expenditures.