A review of astigmatism and its possible genesis

Comparison of different methods of correcting astigmatism in cataract surgery

CLINICAL RELEVANCE

Astigmatism causes a decrement in visual acuity, and deterioration in visual quality.

BACKGROUND

The aim of this study is to compare clear corneal incision (CCI) in the steepest meridian, opposed clear corneal incision (OCCI) and toric intraocular lens implantation methods for the correction of astigmatism in cataract surgery.

METHODS

Total of 93 preoperative patients with the rule corneal astigmatism (between 1.00-3.00 D)underwent uncomplicated cataract surgery are retrospectively included in this study. Whole patients are divided into three groups of equal number of patients of 31 by considering the astigmatism correcting methods that are as follows. Group 1 consists of patients underwent CCI on the steepest meridian, group 2 consists of the patients underwent paired OCCI, and group 3 consists of those with toric intraocular lens implantation. The preoperative and postoperative 3rd month uncorrected distance visual acuity, refraction and, keratometry values, and surgically induced astigmatism values calculated by Alpins method are recorded.

RESULTS

The age, preoperative and postoperative 3rd month spherical, spherical equivalent refraction and keratometry values of the groups are similar (p > 0.05). The preoperative uncorrected distance visual acuity values are similar in whole groups, postoperative uncorrected distance visual acuity values are the highest in group 1, and lowest in group 3 (p = 0.85, p = 0.02, respectively). The preoperative and postoperative 3rd month mean cylinder refraction values are -1.86 D, -1.00 D in group 1, -1.77 D, -0.70 D in group 2, and -1.95 D, -0.40 D in group 3. There is a statistically significant difference among the groups (p = 0.01). The surgically induced astigmatism values are statistically different among the groups [it was 0.46 ± 0.21 in group 1, 0.91 ± 0.44 in group 2, 0.33 ± 0.18 in group 3 (p < 0.001, respectively)].

CONCLUSION

This study indicated that; CCI, paired OCCI, and toric intraocular lens implantation should be preferred and performed for the steepest meridian in low D, middle D, and high D astigmatism patients, respectively. CCI can easily be applied for low to medium D without needing extra skills and tools. On the other hand, toric intraocular lens implantation is a better option for a high astigmatism with proper and accurate planning before the surgery.

Refraction and topographic risk factors for early myopic regression after small-incision lenticule extraction surgery

We sought to evaluate the topographic risk factors for early myopic regression after small-incision lenticule extraction (SMILE). A retrospective case‒control study was conducted, and individuals who underwent SMILE surgery were enrolled. Among them, 406 and 14 eyes were categorized into the nonregression and regression groups, respectively. The preoperative and postoperative parameters in the two groups were collected, including spherical refraction (SE), axial length (AXL) and topographic data. A generalized linear model was adopted to analyze the difference in each parameter between the two groups. After 6 months, UCVA decreased in the regression group, and SE increased in the regression group (both P < 0.05). The increase in the CCT at the thinnest point (P = 0.044), flat corneal curvature (P = 0.012) and TCRP (P = 0.001) were significantly greater in the regression group. Regarding the risk factors for myopic regression, preoperative SE, preoperative sphere power, preoperative AXL, preoperative flat corneal curvature, preoperative SA, early postoperative SE, early postoperative sphere power, early postoperative AXL and early postoperative CCT difference were significantly greater in the regression group (all P < 0.05). The SE, sphere power, AXL, preoperative flat corneal curvature, preoperative SA, and postoperative CCT difference correlate with early myopic regression after SMILE.

Prevalence and risk factors for astigmatism in 7 to 19-year-old students in Xinjiang, China: a cross-sectional study

BACKGROUND

To investigate the prevalence and risk factors for astigmatism in 7-19-year-old students in Xinjiang, China.

METHODS

A school-based, cross-sectional study was conducted on students who underwent refraction examination in Xinjiang, China, between May and December 2019. The prevalence of astigmatism was determined. Astigmatism was defined as cylinder power (C) ≤-0.75 D, undefined astigmatism as ≤-1.50 D, and high astigmatism as C ≤-3.00 D. Astigmatism types were: against-the-rule astigmatism (maximum refraction of the main meridian in 180° ± 30°), with-the-rule astigmatism (maximum refraction of the main meridian at 90°±30°), and oblique astigmatism (all other cases).

RESULTS

Of the 71,838 students examined (51.0% boys, 7 - 19 years old), 25,945 (36.1%, 95%CI: 35.52-36.68%) had astigmatism and 1267 (1.8%, 95%CI: 1.07-2.53%) had high astigmatism. The prevalence of astigmatism was greater in Han individuals (39.6%) compared with the Hui (34.0%), Kazakh (34.0%), Kyrgyz (32.1%), and Uyghur (26.4%) populations. Among the 25,945 students with astigmatism, 19,947 had with-the-rule astigmatism (76.9%), 3405 had against-the-rule astigmatism (13.1%), and 2593 had oblique astigmatism (10.0%). Multivariable logistic regression analysis showed that ethnicity (Han individuals more susceptible), male gender, age, and refractive errors (myopia and hyperopia) were independently associated with astigmatism, high astigmatism, and with-the-rule astigmatism (all P < 0.05).

CONCLUSIONS

The prevalence of astigmatism among children and adolescents in Xinjiang was 36.1%, including 1.8% of high astigmatism. In this population, astigmatism was mainly of the with-the-rule astigmatism type (76.9%). Han ethnicity, male gender, and myopia or hyperopia were independently associated with a high risk of astigmatism.

Compensatory Interactions between Corneal and Internal Astigmatism despite Lifestyle Changes

This study explores whether children's refractive errors and visual behaviors reverted to pre-COVID-19 levels a year after normal schooling resumed in Hong Kong as well as the impact of corneal and internal astigmatism on refractive astigmatism development. Vision survey data and questionnaire results collected in 2022 (n = 119) and 2020 (n = 173) were compared. Cross-sectional data showed similar proportions of astigmatism (cylindrical power ≥ 0.75 D) in the 2020 (49.1%) and 2022 cohorts (55.5%). Despite a 0.28 D increase in corneal astigmatism, a compensatory 0.24 D increase in internal astigmatism of opposite direction kept refractive astigmatism relatively stable. The questionnaire data showed that children spent an additional 0.5 h/day outdoors on weekends post-resumption of normal schooling but engaged in more near-work activities, especially non-screen near-work, by approximately 1 h/day on both weekdays and weekends. These findings were supported by longitudinal data from 72 children who participated in both surveys. This study highlights the significant role of corneal and internal astigmatism in refractive astigmatism changes. Despite the return to in-person classes, children's total near-work time increased and astigmatism remained high. These findings underscore the need for comprehensive strategies to reduce the high environmental risks for refractive error development in children.

Anisometropia and its association with refraction development in highly myopic children

CLINICAL RELEVANCE

Anisometropia can affect visual development in children. Investigations of anisometropia in high myopes would explore potential causes related to anisometropia, highlighting the management of anisometropia in high myopia.

BACKGROUND

The prevalence of anisometropia ranged from 0.6% to 4.3% in general paediatric population and from 7% to 14% in myopes. Anisometropia is regarded as an associated factor for myopia development, while myopia progression is a stimulus driving anisometropic development. The purpose of this study was to investigate the prevalence of anisometropia and its association with refraction development in Chinese children with high myopia.

METHODS

In the cohort study, a total of 1,577 highly myopic (spherical equivalent ≤-5.0D) children aged 4-18 years were included. Refractive parameters (dioptre of sphere, dioptre of cylinder, corneal curvature radius, and axial length) of both eyes were measured after cycloplegia. The prevalence and degree of anisometropia were compared among refractive groups (non-parametric tests or chi-square tests), and regression analyses were used to determine associated factors of anisometropia. The statistical significance was set to P < 0.05 (two-tailed).

RESULTS

In highly myopic children with a mean (standard deviation) age of 13.06 (2.80) years, the proportions of spherical equivalent anisometropia, cylindrical anisometropia and spherical anisometropia ≥1.00 D were 34.5%, 21.9% and 39.9%, respectively. There was more spherical equivalent anisometropia associated with more severe astigmatism (P for trend <0.001). In the multivariate regression analysis, more spherical equivalent anisometropia, cylindrical anisometropia and spherical anisometropia were associated with higher degrees of astigmatism (standard beta = -0.175, -0.148 and -0.191, respectively). More spherical anisometropia was associated with better spherical power (standard beta = 0.116).

CONCLUSION

The proportion of anisometropia in highly myopic children was high, compared with previously reported general population, and more severe anisometropia was associated with higher degree of cylindrical power, but not spherical power.

The prevalence of functional amblyopia and its related risk factors in preschool children in North-Eastern Iran

BACKGROUND

Purpose was to determine the prevalence of amblyopia and its related risk factors in children aged 3-6 years in Bojnurd, north-eastern Iran.

MATERIALS AND METHODS

In this cross-sectional study, from 12,331 children aged 3-6 in Bojnurd, 6600 children participated in annual amblyopic screening program and among them, around 1100 suspected cases were referred for full ophthalmic examinations. Measurement of visual acuity, cycloplegic refraction, subjective refraction, and cover test were performed for all participants. Amblyopia was defined as CDVA of 0.2 LogMar or less in each eye or 2-line difference or more in best-corrected visual acuity between two eyes.

RESULTS

The prevalence of amblyopia was estimated 0.95% (95% confidence interval [CI]: 0.73%-1.2%). There was no relationship between amblyopia with age and genders. Most amblyopic children were hyperopic (61.9%; 95% CI: 48.7-73.8). Strabismus was found in 17.4% of amblyopic patients (95% CI: 9.05%-29.09%). Approximately half of the amblyopic children were anisometropic (55.5%; 95% CI: 42.40%-68.08%). The most common type of amblyopia was anisohyperopic (55.56%; 95% CI: 42.5%-67.5%). The prevalence of bilateral amblyopia was more than unilateral amblyopia. The assessment of data showed that hyperopia, astigmatism, and anisometropia were the most common causes of amblyopia in this study.

CONCLUSIONS

The prevalence of amblyopia was estimated about 1% in north-eastern Iran. Our study indicated a valuable information around the effect of refractive error and anisometropia on amblyopia which could be helpful in designing a comprehensive vision screening program for preschool children.

Comparison of visual outcomes in adult patients with different types of developmental cataracts after toric multifocal intraocular lenses implantation

PURPOSE

 To analyze and compare the visual performance and patient satisfaction following the implantation of toric multifocal intraocular lenses (TMIOLs) in adult patients with different types of developmental cataracts (DC) accompanied by corneal astigmatism (CA).

METHODS

 This is a prospective observational cohort study. Patients diagnosed with DC aged 18-30 years were divided into three groups according to the anatomic location of the lens opacity: cortical, nuclear, and posterior subcapsular (PSC) groups, and implanted with TMIOLs. Visual acuity (VA), postoperative refractive astigmatism (RA), intraocular lens (IOL) rotation, high-order aberrations (HOAs), modulation transfer function (MTF) curve, and Strehl ratio were compared. The functional vision and incidence of photic phenomena were surveyed using questionnaires.

RESULTS

 Fifty-five eyes of 37 patients were enrolled and completed a 1-year follow-up. The mean CA was 2.06 ± 0.79 D preoperatively, and the mean RA was 0.29 ± 0.30 D 3-month postoperatively. The IOL rotation was 2.48° ± 1.89°, with no deviation > 10°. At 12 months, mean uncorrected distance VA improved from 0.93 ± 0.41 preoperatively to 0.08 ± 0.08 logarithm of the minimum angle of resolution (logMAR), mean uncorrected near VA increased from 0.45 ± 0.30 preoperatively to 0.12 ± 0.11 logMAR, and mean uncorrected intermediate VA was 0.14 ± 0.08 logMAR. The cortical and nuclear groups displayed better improvements in uncorrected near and intermediate VA than that in the PSC group. Similar results were observed in the 3-month defocus curves, HOAs, MTF curve, halo incidence, and near vision satisfaction.

CONCLUSION

In adult patients with DC accompanied by CA, TMIOLs implantation achieved good postoperative visual outcomes and significantly reduced glasses dependency. Patients with cortical or nuclear lens opacity showed better whole-course VA and quality of vision, while patients with PSC opacity showed unsatisfactory near vision and suffered more photic phenomena.

Comparison of three different intraocular lens implantation techniques in the absence of capsular support: sutured scleral, haptic flanged intrascleral, and four flanged intrascleral fixations

INTRODUCTION

After lens extraction, if the capsular bag insufficiency occurs, there are different IOL implantation techniques. IOL implantation in the posterior chamber is safer in eyes with low endothelial cell count, peripheral anterior synechiae, shallow anterior chamber, and glaucoma. Alternative approaches for scleral fixation techniques, both with and without sutures, continue to undergo development. In this study, we aimed to compare the postoperative outcomes of the sutured scleral fixation (SSF), haptic flanged intrascleral fixation (HFISF) and four flanged intrascleral fixation (FFISF) IOL implantation techniques in eyes with the absence of capsular support.

MATERIALS AND METHODS

A hundred and thirty-seven aphakic eyes with the absence of capsular support were included in the study. The patients were divided into three groups: group 1-SSF, group 2-HFISF (Yamane technique), and group 3-FFISF. Surgical time in minutes, preoperative and postoperative parameters such as best corrected visual acuity (BCVA), corneal astigmatism, lenticular astigmatism, intraocular pressure (IOP), specular microscopy, central macular thickness (CMT) were recorded. Pseudophacodonesis was assessed at 6 months postoperatively using a slit lamp, and early and late complications were recorded.

RESULTS

Of the 137 eyes, 69 eyes were included in the SSF group, 41 eyes in the HFISF group, and 27 eyes in the FFISF group. No statistically significant differences were observed among the three groups in terms of age, gender, preoperative mean BCVA, corneal astigmatism, IOP, endothelial cell density, and CMT. It was observed that the mean BCVA significantly improved compared to the preoperative visual acuity in all three groups. Postoperative lenticular astigmatism, pseudophacodonesis score, percentage of the endothelial cell loss were found to be higher in FFISF groups. The surgical time was found to be shorter in the HFISF group. IOL decentration was observed in 1.44% of the SSF group and 7.40% of the FFISF group. Cystoid macular edema was observed in 5.79% of the SSF group, 4.87% of the HFISF group, and 7.40% of the FFISF group. Retinal detachment was observed in 1.44% of the SSF group and 7.31% of the HFISF group.

CONCLUSIONS

The optimal technique for treating aphakia without capsular support remains uncertain. Surgeons are tasked with a complex decision, aiming for both excellent vision and minimal risk. This decision is based on their expertise, the distinctive ocular condition of the patient, and the availability of essential operating room equipment. In this study, the following findings were observed: in the HFISF technique, the average surgical time was found to be shorter, the SSF technique demonstrated greater stability in terms of astigmatism and pseudophacodonesis and the FFISF technique was recognized for its relatively straightforward application method. It is important to note that the three IOL implantation techniques yielded comparable outcomes in terms of postoperative BCVA, as well as early and late complications.

Minimum Corneal Diameter and Anterior Steep Axis Curvature Share the Same Meridian: A Novel Finding

PURPOSE

To define the external scleral sulcus (ESS) on a Scheimpflug image and use it for a morphometric analysis of corneal diameter (CD).

DESIGN

Retrospective, cross-sectional study of pediatric Asian-Indian eyes.

METHODS

One random eye of 353 subjects between 5 and 18 years underwent 25-scan Pentacam HR imaging. For all scans, densitometry values along the anterior corneal edge were recorded and differentiated. The peaks on the differentiated curve were chosen as the ESS points, and this distance between them was called CD. Vertical (vCD), maximum (maxCD), minimum (minCD) CD and their meridians were defined. Multiple regression models (MRMs) with CD and other Pentacam parameters were built to predict astigmatism and its axis, mean keratometry (Kmean), and Belin/Ambrósio enhanced ectasia display deviation (BAD-D). MRMs were validated using intraclass correlation coefficient (ICC). Estimated horizontal CD (hCD) was validated against digital caliper measurement using ICC.

RESULTS

The ICC (95% CI) between caliper and hCD was 0.96 (0.93, 0.97). MRM predictions (P < .001) used CD parameters, anterior chamber depth, corneal volume and distance from the corneal thinnest location to apex. These predictions achieved an ICC of 0.34 (0.18, 0.46), 0.82 (0.78, 0.86), 0.87 (0.84, 0.89), and 0.81 (0.76, 0.84), respectively. The astigmatism axis prediction depended on the minCD and maxCD meridians. Its within-subject SD (4.97°) was less than 2 consecutive Pentacam scan angles (7.2°).

CONCLUSIONS

The CD metric strongly correlated with the astigmatism axis, keratometry, and BAD-D. Its spatial description may be significant in corneal treatment planning and disease diagnoses.

Refractive and corneal astigmatism in Chinese 4-15 years old children: prevalence and risk factors

BACKGROUND

To investigate the prevalence and risk factors of refractive astigmatism (RA) and corneal astigmatism (CA) in preschool children and school-aged children in Shanghai, China.

METHODS

In this school-based, cross-sectional study, 4-15 years old children across three learning stages of kindergarten, primary school, and junior high school underwent noncycloplegic autorefraction and completed comprehensive questionnaires involving time spent on daily homework and outdoor activities. Data from the right eyes were analysed.

RESULTS

Overall, 7084 children (mean ± standard deviation (SD) of age: 8.08 ± 3.11 years) were included, and the prevalence rates of RA/CA ( ≤ - 1.0 D) in children were 15.8%/64% in kindergartens, 16.5%/65% in primary schools, and 32.8%/76.9% in junior high schools. The magnitude and prevalence of RA and CA all increased with age or with learning stage (all P < 0.001). The presence of RA was associated with more myopic spherical power (odds ratio (OR) 0.956, P = 0.021), junior high school (OR 1.973, P < 0.001), longer homework time on weekdays (OR 1.074, P = 0.029), and shorter outdoor activity time on weekends (odds ratio 0.929, P = 0.013).

CONCLUSION

In the wide age range of 4 to 15 years, the magnitude and prevalence of RA and CA increased with the learning stage, and these increases mainly began at the primary school stage. Factors, including longer homework time and shorter outdoor time were correlated with the presence of RA.

Secondhand smoke exposure and ocular health: A systematic review

The toxicology of secondhand smoke (SHS), along with the harm of its exposure to human health, has been generally acknowledged; however, specific evidence is lacking on the association between SHS exposure and ocular health. In this systematic review (PROSPERO registration number: CRD42022247992), we included 55 original articles published by 12 May 2023, which dealt with SHS exposure and ocular disorders, such as eye irritation, conjunctivitis, dry eye diseases, uveitis, myopia, astigmatism, contact lens discomfort, age-related macular degeneration, glaucoma, and thyroid eye disease that addressed the ocular neurovascular structures of the macular, retinal nerve fiber layer, choroid, and corneal biomechanical parameters. We found compelling correlational evidence for eye irritation, conjunctivitis, and dry eye symptoms-supporting that SHS exposure was positively associated with inflammatory and allergic changes in the eyes. Yet, evidence about the associations between SHS exposure and other ocular disorders, structures, and parameters is still limited or controversial. Given the limitations of existing literature, more investigations with high quality and rigorous design are warranted to elucidate the potentially harmful effects of SHS exposure on ocular health.

Progression pattern of non-amblyopic Anisomyopic eyes compared to Isomyopic eyes

This study aimed to determine the progression pattern of non-amblyopic anisomyopic children from ages 6 to 16 years. This retrospective study analyzed the electronic medical records of 8680 myopic children who visited Sankara Nethralaya, Chennai, India over eight years (2009 to 2017). A total of 711 records were retrieved based on inclusion criteria. In addition, 423 records out of 711 had consecutive follow-up for three years (baseline plus three follow-up visits) and were considered to determine the progression pattern. The cycloplegic sphero-cylindrical refraction was taken for analysis and converted to vector notation of M (SE), J0, and J45. Anisomyopia referred to the interocular difference of myopic SE of ≥ 1 D whereas isomyopia referred to the interocular difference of myopic SE of < 1 D. Based on the refraction of the less ametropic eye, anisomyopes were further categorized into bilateral anisometropic myopia (BAM) and unilateral anisometropic myopia (UAM). The isomyopic cohort showed a mean annual progression of -0.49 ± 0.54 D (median [IQR] -0.38 D [{-0.75}-0.00]). In BAM, the mean annual progression of the more myopic eye was -0.45 ± 0.55 D (median [IQR] -0.38 D [{-0.75}-0.00]), and the less myopic eye was -0.37 ± 0.55 D (median [IQR] -0.25 D [{-0.63}-0.00]). This difference was significant (t (212) = -2.14, p < 0.05). In UAM, the myopic eyes (-0.39 ± 0.51 D; median [IQR] -0.25 D [{-0.75}-0.00]) showed a statistically significant higher mean annual progression compared to emmetropic eyes (-0.22 ± 0.36 D; median [IQR] 0.00 D [{-0.44}-0.00]; t (96) = -3.30, p < 0.001). In terms of progression trend, in the BAM group, the rate of change of mean SE between the more myopic and the less myopic eyes were similar (-1.12 ± 1.20 D; median [IQR] -1.13 D [{-2.00}-{-0.38}] vs. -1.05 ± 1.25 D; median [IQR] -0.88 D [{-1.75}-{-0.13}]; t (138) = -0.64, p > 0.05). However, the more myopic eyes of UAM showed a higher myopic trend compared to the emmetropic eyes (-1.37 ± 1.06 D; median [IQR] -1.32 D [{-2.13}-{-0.50}] vs. -0.96 ± 1.11 D; median [IQR] -0.75 D [{-1.56}-{-0.25}]; t (61) = -2.74, p < 0.05).   Conclusion: Children with BAM and UAM eyes exhibit different progression patterns from each other. While the rate of the refractive shift in myopic eyes of UAM is similar to isomyopic eyes, BAM eyes present a slower rate of progression than isomyopic eyes. What is Known: • The rate of change of refraction in anisomyopes is higher compared to isomyopic children. • Less myopic eyes tend to shift towards more myopia while more myopic eyes show stable refraction. What is New: • The progression pattern of bilateral anisometropic myopia and unilateral anisometropic myopia differ from one another. • While the rate of the refractive shift in myopic eyes of unilateral anisometropic myopia is similar to isomyopic eyes, bilateral anisometropic myopia eyes present a slower rate of progression than isomyopic eyes. • The pattern of change in the interocular difference of anisometropia depends on the laterality (bilateral or unilateral ametropia), and degree of spherical equivalent in the more ametropic eye.

Pre-Operative Ocular Findings and Long-Term Follow-Up in a Large Cohort of Non-Syndromic Unicoronal Craniosynostosis

(1) Background: Non-syndromic unicoronal craniosynostosis (UCS) is associated with a high prevalence of ocular anomalies. Currently, the etiology of this association remains obscure, however, it is presumed to be primarily attributed to their orbital malformations and/or secondary to craniofacial surgery. We assessed pre-operative ophthalmological examinations of non-syndromic UCS patients and compared them with their postoperative outcomes and long-term follow-up. (2) Methods: A retrospective case series was conducted on medical records of patients with non-syndromic UCS at Sophia Children's Hospital, Rotterdam. Ophthalmologic examinations were collected at different time periods: T1 (first visit), T2 (<1 year after cranioplasty), and T3 (long-term follow-up at last visit). The McNemar's test was used for statistical analysis. (3) Results: A total of 101 patients were included, for whom examinations were available at T1 and T3. Patients had a mean age of 2.8 years (±2.7) and 9.5 (±4.9) at T1 and T3, respectively. At T1, 52 patients (51.5%) were diagnosed with strabismus, and 61 patients (60.4%) at T3. Vertical strabismus increased significantly from 23 patients (22.8%) at T1 to 36 patients (35.6%) at T3 (p = 0.011). Followed by astigmatism, which increased significantly from 38 (37.6%) at T1 to 59 (58.4%) patients at T3 (p = 0.001). T1 was available in 20 patients prior to fronto-orbital advancement (FOA), therefore, a sub-analysis was conducted on these patients, which was followed shortly after FOA at T2. Prior to FOA, strabismus was present in 11 patients (55.0%) and in 12 patients (60.0%) at T2. After FOA, strabismus worsened in two patients. (4) Conclusions: This study showed the high prevalence of ocular anomalies in patients with non-syndromic UCS before and after cranioplasty and at long-term follow-up. The findings of this study show that ophthalmic and orthoptic examinations are an important part of the optimal treatment of patients with non-syndromic UCS.

Association of PDGFRA polymorphisms with the risk of corneal astigmatism in a Japanese population

Corneal astigmatism is reportedly associated with polymorphisms of the platelet-derived growth factor receptor alpha (PDGFRA) gene region in Asian populations of Chinese, Malay, and Indian ancestry and populations of European ancestry. In this study, we investigated whether these PDGFRA polymorphisms are associated with corneal astigmatism in a Japanese population. We recruited 1,535 cases with corneal astigmatism (mean corneal cylinder power across both eyes: ≤  - 0.75 diopters [D]) and 842 controls (> - 0.75 D) to genotype 13 single-nucleotide polymorphisms (SNPs) in the PDGFRA gene region. We also performed imputation analysis in the region, with 179 imputed SNPs included in the statistical analyses. The PDGFRA SNPs were not significantly associated with the cases with corneal astigmatism ≤  - 0.75 D. However, the odds ratios (ORs) of the minor alleles of SNPs in the upstream region of PDGFRA, including rs7673984, rs4864857, and rs11133315, tended to increase according to the degree of corneal astigmatism, and these SNPs were significantly associated with the cases with corneal astigmatism ≤  - 1.25 D or ≤  - 1.50 D (Pc < 0.05, OR = 1.34-1.39). These results suggest that PDGFRA SNPs play a potential role in the development of greater corneal astigmatism.

Effects of atropine 0.01% on refractive errors in children with myopia

Background

Little is known about changes in astigmatism during atropine treatment. We aimed to explore the effects of atropine 0.01% eye drops on both spherical and cylindrical refractive errors in myopic children.

Methods

Children aged 6-14 years with myopia ≥ -6.00 D and < -0.50 D, and total astigmatism > -2.00 D in at least one eye were enrolled. Subjects were randomised either to receive atropine 0.01% once nightly with single-vision lenses or simply to wear single-vision lenses and were followed up at 3-month intervals. Cycloplegic refraction and axial length were measured. The magnitude and direction of total astigmatism (TA), corneal astigmatism (CA), and residual astigmatism (RA) were evaluated.

Results

Overall, 119 eyes (69 eyes in the atropine group and 50 eyes in the control group) were included in the final analyses after 9 months. Atropine-treated eyes showed significantly less progression of myopia than did control eyes (spherical equivalent: -0.35 ± 0.33 vs. -0.56 ± 0.49 D, p = 0.001; axial length: 0.20 ± 0.19 vs. 0.33 ± 0.19 mm, p < 0.001). Compared with control eyes (-0.04 ± 0.23 D), a significant increase in TA was observed in the atropine-treated eyes (-0.14 ± 0.29 D); this was mainly attributed to the increase in CA (-0.17 ± 0.26 D) rather than the minor decrease in RA (0.02 ± 0.32 D).

Conclusions

Atropine 0.01% was effective in preventing myopia progression, whereas 9 months of atropine treatment resulted in a clinically small, but statistically significant increase in TA in myopic Chinese children.

Dynamic correction of astigmatism

For the correction of defocus and astigmatism, mechanical approaches are well known, but there is a need for a non-mechanical, electrically tunable optical system that could provide both focus and astigmatism power correction with an adjustable axis. The optical system presented here is composed of three liquid-crystal-based tunable cylindrical lenses that are simple, low cost, and having a compact structure. Potential applications of the concept device include smart eyeglasses, virtual reality (VR)/ augmented reality (AR) head-mounted displays (HMDs), and optical systems subject to thermal or mechanical distortion. Details of the concept, design method, numerical computer simulations of the proposed device, as well as characterization of a prototype, are provided in this work.

Epidemiology and Burden of Astigmatism: A Systematic Literature Review

SIGNIFICANCE

This is the first literature review to report the epidemiology, patient burden, and economic burden of astigmatism in the general adult population. The unmet needs of astigmatism patients with coexisting ocular conditions (cataract, glaucoma, dry eye, presbyopia, or macular degeneration) and risks associated with untreated astigmatism are also reviewed and reported.

PURPOSE

This study aimed to identify, report, and summarize the published literature on epidemiology, patient burden, and economic burden of astigmatism using a systematic literature review.

METHODS

MEDLINE, EMBASE, and Cochrane Library databases were searched (January 1996 to May 2021). Search results were limited to the English language. Proceedings (2018 to 2021) from ophthalmology congresses were searched along with gray literature using the Google Scholar platform.

RESULTS

The literature search yielded 6804 citations, of which 125 met the inclusion criteria (epidemiology, 68; patient burden, 60; economic burden, 6). Astigmatism prevalence in the general population varied from 8 to 62%, with higher rates in individuals 70 years or older. The prevalence of with-the-rule astigmatism was higher in individuals 40 years or younger, whereas rates of against-the-rule and oblique astigmatism increased with age. Astigmatic patients experienced decreased vision quality, increased glare (53 to 77%), haloes (28 to 80%), night-time driving difficulties (66%), falls, and spectacle dependence (45 to 85%). Astigmatic patients performed vision-related tasks slower (1 D, 9% slower; 2 D, 29% slower) and made more errors (1 D, 38% more errors; 2 D, 370% more errors) compared with fully corrected individuals. In cataract patients with astigmatism, the annual mean per-patient productivity loss costs ranged from €55 ($71) to €84 ($108), and mean informal care costs ranged from €30 ($39) to €55 ($71) with a mean of 2.3 to 4.1 hours spent on informal care.

CONCLUSIONS

Uncorrected astigmatism decreases patients' vision-related quality of life, decreases productivity among working-age adults, and poses an economic burden on patients and their families.

Refractive development I: Biometric changes during emmetropisation

PURPOSE

Although there are many reports on ocular growth, these data are often fragmented into separate parameters or for limited age ranges. This work intends to create an overview of normal eye growth (i.e., in absence of myopisation) for the period before birth until 18 years of age.

METHODS

The data for this analysis were taken from a search of six literature databases using keywords such as "[Parameter] & [age group]", with [Parameter] the ocular parameter under study and [age group] an indication of age. This yielded 34,409 references that, after screening of title, abstract and text, left 294 references with usable data. Where possible, additional parameters were calculated, such as the Bennett crystalline lens power, whole eye power and axial power.

RESULTS

There were 3422 average values for 17 parameters, calculated over a combined total of 679,398 individually measured or calculated values. The age-related change in refractive error was best fitted by a sum of four exponentials (r²  = 0.58), while all other biometric parameters could be fitted well by a sum of two exponentials and a linear term ('bi-exponential function'; r² range: 0.64-0.99). The first exponential of the bi-exponential fits typically reached 95% of its end value before 18 months, suggesting that these reached genetically pre-programmed passive growth. The second exponentials reached this point between 4 years of age for the anterior curvature and well past adulthood for most lenticular dimensions, suggesting that this part represents the active control underlying emmetropisation. The ocular components each have different growth rates, but growth rate changes occur simultaneously at first and then act independently after birth.

CONCLUSIONS

Most biometric parameters grow according to a bi-exponential pattern associated with passive and actively modulated eye growth. This may form an interesting reference to understand myopisation.

Meridional Attentional Asymmetries in Astigmatic Eyes

Purpose

To investigate the impact of attention orientation in young myopic adults with astigmatism.

Methods

The effect of attention on foveal meridional performance and anisotropy was measured in corrected myopes with various levels of astigmatism (with-the-rule astigmatism ≤ -0.75D, Axis: 180 ± 20) using orientation-based attention. Attention was manipulated by instructing subjects to attend to either the horizontal or the vertical line of a central pre-stimulus (a pulsed cross) along separate blocks of trials. For each attention condition, meridional acuity and reaction times were measured via an annulus Gabor target situated remotely from the cross and presented at random horizontally and vertically in a two-alternative forced-choice employing two interleaved staircase procedures (one-up/one-down). Attention modulations were estimated by the difference in performance between horizontal and vertical attention.

Results

Foveal meridional performance and anisotropy were strongly affected by the orientation of attention, which appeared critical for the enhancement of reaction times and resolution. Under congruent orienting of attention, foveal meridional anisotropy was correlated with the amount of defocus for both reaction time and resolution, demonstrating greater vertical performance than horizontal performance as myopia increased. Compatible with an attentional compensation of blur through optimal orienting of attention, vertical attention enhanced reaction times compared to horizontal attention and was accompanied by an increase in overall acuity when myopia increased. Increased astigmatism was associated with smaller attention effects and asymmetry, suggesting potential deficits in the compensation of blur in astigmatic eyes.

Conclusion

Collectively, attention to orientation plays a significant role in horizontal-vertical foveal meridional anisotropy and can modulate the asymmetry of foveal perception imposed by the optics of the eye in episodes of uncorrected vision. Further work is necessary to understand how attention and refractive errors interact during visual development. These results may have practical implications for methods to enhance vision with attention training in myopic astigmats.

Corneal and Whole-Eye Higher Order Aberrations Do Not Correlate With Ocular Residual Astigmatism in Prepresbyopic Refractive Surgery Candidates

PURPOSE

Ocular residual astigmatism (ORA) is the proportion of manifest astigmatism that is not explained by anterior corneal astigmatism. The role of higher order aberrations (HOAs) in the level of ORA has not been profoundly studied. The purpose of this study was to evaluate the effect of different corneal and whole-eye HOAs on levels of ORA using a multivariate modeling approach.

METHODS

This is a retrospective analytical study including a sample of healthy refractive surgery candidates. One eye of every patient was randomly selected. A total of 294 eyes from an equal number of patients were included. Corneal and whole-eye HOAs were measured with a Pentacam AXL Wave, and subjective manifest refraction was taken. Astigmatism values were converted into power vectors and ORA was calculated. The Spearman rank-order correlation was initially used to explore correlation between HOA and ORA. All variables with a P value under 0.10 were included into a multiple linear regression model to explore this correlation adjusting for confounding variables.

RESULTS

The mean age was 28.81 ± 5.40 years. Simple bivariate correlation was significant for root mean square (RMS) total, RMS lower order aberrations, RMS HOAs, defocus, and vertical astigmatism. After being included into a multivariate regression model adjusting for confounding variables, the only variable that was significant was RMS total [F(3, 282) = 78.977; P < 0.001; adjusted R2 = 0.451]. For every μm increase in corneal RMS total, ORA increases by 0.135 diopters. About 45% of variability in ORA can be explained by corneal RMS total, corneal J0, and manifest J0. No individual HOA correlated with ORA in the multivariate regression model.

CONCLUSIONS

ORA increases with general corneal irregularity, especially regular astigmatism. Irregular astigmatism expressed by corneal and whole-eye HOAs does not seem to be a significant contributor of ORA in healthy refractive surgery candidates.

Age- and gender-related characteristics of astigmatism in a myopic population

Purpose

To explore age- and gender-related differences of refractive and corneal astigmatism in myopic patients looking for refractive surgery.

Design

A retrospective cross-sectional study.

Materials and methods

The medical files of candidates looking for corneal refractive surgery between 2019 and 2021 were reviewed, demographic and refractive parameters including age, gender, refractive status, and corneal parameters were analyzed.

Results

A total of 1,417 eyes of 1,417 patients (453 males and 964 females) were included. Males had thicker cornea than females, while females had steeper cornea than males, there was no gender-related difference in refractive and corneal astigmatism depending on patients’ age. There was no difference in refractive astigmatism among different age group from 18 to 50 years, while corneal astigmatism had a shift from with-the rule (WTR) to against-the-rule (ATR) with increasing age. Age, central corneal thickness (CCT), sphere, refractive astigmatism (RA), and corneal curvature (Km) were correlated with corneal astigmatism (CA) (standardized coefficients of are 0.006, p = 0.011 for age, −0.001, p = 0.004 for CCT, and −0.027, p < 0.001 for sphere, 0.61, p < 0.001 for RA, −0.05, p < 0.001 for corneal curvature).

Conclusion

Refractive astigmatism is stable until the age of 50 years in myopic patients looking for refractive surgery, while corneal astigmatism showed a shift from WTR to ATR with advancing age. Age, CCT, sphere, refractive astigmatism and corneal curvature (Km) were correlated with corneal astigmatism.

Using electronic medical record data to establish and monitor the distribution of refractive errors. JOURNAL OF OPTOMETRY 2022;15 Suppl 1:S32-S42. [PMID: 36220741 PMCID: PMC9732486 DOI: 10.1016/j.optom.2022.09.001]

OBJECTIVE

To establish the baseline distribution of refractive errors and associated factors amongst a population that attended primary care optometry clinics.

DESIGN

Retrospective cross sectional cohort study of electronic medical records (EMR).

METHODS

Electronic medical record data was extracted from forty optometry clinics, representing a mix of urban and rural areas in Ireland. The analysis was confined to demographic and clinical data gathered over a sixty-month period between 2015 and 2019. Distribution rates were calculated using the absolute and relative frequencies of refractive error in the dataset, stratified for age and gender using the following definitions: high myopia ≤ -6.00 D, myopia ≤ -0.50 D, hyperopia ≥ +0.50 D, astigmatism ≤ -0.75 DC and anisometropia ≥ 1.00 D. Visual acuity data was used to explore vision impairment rates in the population. Further analysis was carried out on a gender and age-adjusted subset of the EMR data, to match the proportion of patients in each age grouping to the population distribution in the most recent (2016) Irish census.

RESULTS

153,598 clinic records were eligible for analysis. Refractive errors ranged from -26.00 to +18.50 D. Myopia was present in 32.7%, of which high myopia represented 2.4%, hyperopia in 40.1%, astigmatism in 38.3% and anisometropia in 13.4% of participants. The clinic distribution of hyperopia, astigmatism and anisometropia peaked in older age groups, whilst the myopia burden was highest amongst people in their twenties. A higher proportion of females were myopic, whilst a higher proportion of males were hyperopic and astigmatic. Vision impairment (LogMAR > 0.3) was present in 2.4% of participants. In the gender and age- adjusted distribution model, myopia was the most common refractive state, affecting 38.8% of patients.

CONCLUSION

Although EMR data is not representative of the population as a whole, it is likely to provide a reasonable representation of the distribution of clinically significant (symptomatic) refractive errors. In the absence of any ongoing traditional epidemiological studies of refractive error in Ireland, this study establishes, for the first time, the distribution of refractive errors observed in clinical practice settings. This will serve as a baseline for future temporal trend analysis of the changing pattern of the distribution of refractive error in EMR data. This methodology could be deployed as a useful epidemiological resource in similar settings where primary eyecare coverage for the management of refractive error is well established.

Strain-tunable optical microlens arrays with deformable wrinkles for spatially coordinated image projection on a security substrate

As a new concept in materials design, a variety of strategies have been developed to fabricate optical microlens arrays (MLAs) that enable the miniaturization of optical systems on the micro/nanoscale to improve their characteristic performance with unique optical functionality. In this paper, we introduce a cost-effective and facile fabrication process on a large scale up to ~15 inches via sequential lithographic methods to produce thin and deformable hexagonally arranged MLAs consisting of polydimethylsiloxane (PDMS). Simple employment of oxygen plasma treatment on the prestrained MLAs effectively harnessed the spontaneous formation of highly uniform nanowrinkled structures all over the surface of the elastomeric microlenses. With strain-controlled tunability, unexpected optical diffraction patterns were characterized by the interference combination effect of the microlens and deformable nanowrinkles. Consequently, the hierarchically structured MLAs presented here have the potential to produce desirable spatial arrangements, which may provide easily accessible opportunities to realize microlens-based technology by tunable focal lengths for more advanced micro-optical devices and imaging projection elements on unconventional security substrates.

Bi-directional Refractive Compensation for With-the-Rule and Against-the-Rule Astigmatism in Young Adults

Purpose

The purpose of this study was to investigate the short-term effect of imposing astigmatism on the refractive states of young adults.

Methods

Nineteen visually healthy low-astigmatic young adults (age = 20.94 ± 0.37 years; spherical-equivalent errors [M] = -1.47 ± 0.23 diopters [D]; cylindrical errors = -0.32 ± 0.05 D) were recruited. They were asked to wear a trial frame with treated and control lenses while watching a video for an hour. In three separate visits, the treated eye was exposed to one of three defocused conditions in random sequence: (1) with-the-rule (WTR) astigmatism = +3.00 DC × 180 degrees; (2) against-the-rule (ATR) astigmatism = +3.00 DC × 90 degrees; and (3) spherical defocus (SPH) = +3.00 DS. The control eye was fully corrected optically. Before and after watching the video, non-cycloplegic autorefraction was performed over the trial lenses. Refractive errors were decomposed into M, J0, and J45 astigmatism. Interocular differences in refractions (treated eye - control eye) were analyzed.

Results

After participants watched the video with monocular astigmatic defocus for an hour, the magnitude of the J0 astigmatism was significantly reduced by 0.25 ± 0.10 D in both WTR (from +1.53 ± 0.07 D to +1.28 ± 0.09 D) and 0.39 ± 0.15 D in ATR conditions (from -1.33 ± 0.06 D to -0.94 ± 0.18 D), suggesting an active compensation. In contrast, changes in J0 astigmatism were not significant in the SPH condition. No compensatory changes in J45 astigmatism or M were found under any conditions.

Conclusions

Watching a video for an hour with astigmatic defocus induced bidirectional, compensatory changes in astigmatic components, suggesting that refractive components of young adults are moldable to compensate for orientation-specific astigmatic blur over a short period.

Temporal RIT-Eyes: From Real Infrared Eye-Images to Synthetic Sequences of Gaze Behavior

Current methods for segmenting eye imagery into skin, sclera, pupil, and iris cannot leverage information about eye motion. This is because the datasets on which models are trained are limited to temporally non-contiguous frames. We present Temporal RIT-Eyes, a Blender pipeline that draws data from real eye videos for the rendering of synthetic imagery depicting natural gaze dynamics. These sequences are accompanied by ground-truth segmentation maps that may be used for training image-segmentation networks. Temporal RIT-Eyes relies on a novel method for the extraction of 3D eyelid pose (top and bottom apex of eyelids/eyeball boundary) from raw eye images for the rendering of gaze-dependent eyelid pose and blink behavior. The pipeline is parameterized to vary in appearance, eye/head/camera/illuminant geometry, and environment settings (indoor/outdoor). We present two open-source datasets of synthetic eye imagery: sGiW is a set of synthetic-image sequences whose dynamics are modeled on those of the Gaze in Wild dataset, and sOpenEDS2 is a series of temporally non-contiguous eye images that approximate the OpenEDS-2019 dataset. We also analyze and demonstrate the quality of the rendered dataset qualitatively and show significant overlap between latent-space representations of the source and the rendered datasets.

Refractive error characteristics and influence on ocular parameters in patients with unilateral congenital ptosis

Background

The study aimed to investigate the difference in refractive status and ocular parameters between ptotic and fellow eyes in patients with unilateral congenital ptosis.

Methods

Thirty patients (53% males, age 22.00 ± 11.41 years) with unilateral congenital ptosis diagnosed and treated at the First Affiliated Hospital of Sun-yat Sen University were enrolled and underwent detailed refractive examinations from March 2019 to February 2022. Ocular biometric measurements were performed by an IOL Master 700 biometer. The differences in refractive error characteristics, best-corrected visual acuity (BCVA), and ocular parameters including axial length (AL), central corneal thickness (CCT), aqueous depth (AQD), anterior chamber depth (ACD), lens thickness (LT), and keratometry values between ptotic and fellow eyes were analysed.

Results

A lower BCVA (logMAR, median (IQR), 0.00 (− 0.13,0.00), P = 0.009) and a higher incidence of amblyopia (n (%), 7(23%), P = 0.016) were observed in ptotic eyes. The CCT of ptotic eyes was greater than that of fellow eyes (mean ± SD, 539.83 ± 26.73 μm, P < 0.001). The keratometry values at the flat axis (K1) and mean corneal power (Km) were smaller in ptotic eyes (mean ± SD, 42.11 ± 1.49 D, 42.68 ± 1.52 D, respectively, both P = 0.001). There was no significant difference in AL between ptotic and fellow eyes.

Conclusions

Congenital ptosis influences ocular parameters, mainly causing a thicker and flatter cornea. Patients with unilateral congenital ptosis might have lower BCVA in the ptotic eyes.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12886-022-02511-x.

Distribution of Astigmatism among School Children Who Fail Vision Screening in South India

PURPOSE

The purpose of this study is to report the distribution of astigmatism among school children in South India.

METHODS

The study was conducted as part of a national school eye screening project named 'Refractive Error Among Children' (REACH) between 6 and 17 years of age. Children underwent presenting visual acuity screening, external eye examination, screening for color vision deficiency, and non-strabismic binocular vision anomalies. Those who failed screening underwent, objective and subjective refraction, and identification of other ocular conditions. Astigmatism was defined as cylindrical power greater than 0.50D. Refractive errors were classified into myopia (≤0.50D), hyperopia (≥0.75D), and other refractive errors (between -0.50D and +0.75D). The data on astigmatism were analyzed and were deduced into its vector components (M, J0 and J45). Descriptive statistics and regression analysis were performed.

RESULTS

Data of 245,565 children from 1047 schools were taken for analysis. The average age was 11.63 ± 3.32 (range:6-17) years. After screening, refractive errors and astigmatism was found to be 6.57% (n = 16157) and 3.69% (n = 9064), respectively. Astigmatism among children aged 6 to 10 years was 1.37%. The mean cylindrical power, J0, and J45 was found to be 1.93 ± 1.06D, 0.06 ± 0.59D, and 0.43 ± 0.81D, respectively. Linear regression showed a decreasing trend in the cylindrical component (p < .001) and shift towards less positive J0 values (p < .001). Higher proportions of astigmatism more than 1.50 D (1.83%,n = 4578) and unilateral astigmatism (1.20%,n = 2952) are evident among refractive errors.

CONCLUSION

More than 50% of children who failed vision screening with refractive errors presented with astigmatism. Prevalence was higher among primary school children. Presence of higher magnitude and unilateral astigmatism is amblyogenic and needs early intervention.

Influence of Ocular Residual Astigmatism on the Correction of Myopic Astigmatism by Toric Implantable Collamer Lens: A Comparative Study With Femtosecond Laser Small Incision Lenticule Extraction

Purpose

To evaluate the influence of the origin of astigmatism on the correction of myopic astigmatism by toric implantable collamer lens (TICL) and compare it with femtosecond laser small incision lenticule extraction (SMILE).

Methods

Ocular residual astigmatism (ORA) was determined by vector analysis using manifest refraction and Scheimpflug camera imaging of the anterior cornea. One-to-one matching between the TICL and SMILE groups was performed by preoperative manifest refractive astigmatism (RA) and ORA, tolerating a maximum difference of 0.50 diopter (D) for RA and 0.25 D for ORA. Patients of each group were further divided into groups according to ORA (high &gt; 1.0 D; low ≤ 1.0 D). The baseline and 12-month postoperative data were analyzed. Data are expressed as mean ± standard deviation (SD). A value of p less than 0.05 was considered statistically significant.

Results

For the TICL group, no significant differences in the postoperative RA, safety index, efficacy index, index of success (IOS), correction index (CI), and angle of error (AOE) were found between high (n = 36) and low ORA (n = 36) groups (Mann–Whitney U test, p &gt; 0.05). For the SMILE group, the postoperative RA (high: −0.67 ± 0.43 D, low: −0.39 ± 0.29 D, Mann–Whitney U test, p = 0.003) and IOS (high: 0.50 ± 0.43, low: 0.25 ± 0.23, Mann–Whitney U test, p = 0.003) were greater in the high ORA group. When comparing TICL and SMILE groups, the mean postoperative RA (TICL: −0.48 ± 0.29 D, SMILE: −0.67 ± 0.43 D, Mann–Whitney U test, p = 0.03) and IOS (TICL: 0.32 ± 0.23, SMILE: 0.50 ± 0.43, Mann–Whitney U test, p = 0.03) were significantly higher in the SMILE group when the ORA was &gt;1.0 D.

Conclusion

Both TICL and SMILE are effective in correcting myopic astigmatism. ORA has a lesser effect on TICL than on SMILE.

A comparative study of Pentacam indices in various types and severities of refractive error in candidates for photorefractive keratectomy (PRK) surgery

This study aimed to specify Pentacam indices in patients who suffered from different types of refractive error and underwent photorefractive keratectomy (PRK) surgery. It is a descriptive cross-sectional study carried out on 1125 patients (2215 eye samples) who underwent PRK surgery in the Noor Surgical Center of Ardabil, Iran, over a 5 year period (2014-2018). A particular checklist was provided to patients, which consisted of demographic data, pachymetry test, keratometry, refractive error, corneal-thickness indices, and corneal surface area indices. The data were analysed using the statistical analysis package of IBM^® V25. The mean age of the participants in this study was 28.48±6.82 years, and the ratio of women to men was 66.4%. It was observed that the differences between angle, volume, the depth of the anterior chamber, IVA, and ISV were significant (P=0.00) when compared to each other in all types of refractive errors. High myopes had significantly higher K_max front than low myopes (P=0.00). In astigmatism patients, the K_max in front of the cornea in extreme type was significantly higher than in moderate (P=0.00) and high (P=0.01) types. High myopes had significantly lower R_min than mild myopes (P=0.02), and extreme astigmatism had significantly lower R_min than high (P=0.014) and moderate types (P=0.013). The data from this study revealed that in patients undergoing PRK surgery, some Pentacam indices could be related to some types of refractive error, and in some of these indices, there are statistically significant differences between different severities of refractive errors. Therefore, their preoperative evaluation is very important.

Prevalence of Refractive Error in School Children in Suining City of Sichuan Province, China: A School-Based Cross-Sectional Study

Objective

To investigate the prevalence of refractive errors among school children in Suining City, Sichuan Province, and to provide a scientific basis for prevention and control of myopia.

Methods

This was a school-based cross-sectional study. Children aged 6-15 years were selected from kindergartens, primary schools, and middle schools in the urban setting of Suining City. The children underwent ocular examination including measurement of uncorrected visual acuity (UCVA), visual acuity when wearing glasses, and noncycloplegic autorefractometry.

Results

Of the 1200 eligible students, 1138 children (94.8%), 553 of them girls (47.4%), participated. The mean age was 10.64 ± 2.89 years. The prevalence of myopia, hyperopia, astigmatism, and emmetropia was 59.1% (95% confidence interval (CI): 57.6, 60.5), 5.0% (95% CI: 4.7, 6.1), 38.4% (95% CI: 55.5, 58.5), and 25% (95% CI: 23.7, 26.2), respectively. In univariate analysis, the prevalence of myopia was correlated with age, female gender, and learning stage. The prevalence of hyperopia and astigmatism was correlated with age and learning stage. The prevalence of mild myopia, moderate myopia, and high myopia in the 1138 students was 17.7%, 41.4%, and 3.3%, respectively. The prevalence of mild, moderate, and high myopia all increased with age and learning stage. The prevalence of myopia differed by gender. The mean spherical equivalents of the right and left eyes were -1.40 ± 1.99 diopters (D) and -1.29 ± 1.93 D, respectively, and the median values were -0.75 D and -0.6 D, respectively. The mean spherical equivalent increased with age, learning stage, and female gender.

Conclusions

The most common type of refractive error was myopia which was associated with higher age, female gender, and higher learning stage. This study provides new data and recommendations for myopia-control in school-aged children in Sichuan province.

The Distribution Pattern of Ocular Residual Astigmatism in Chinese Myopic Patients

Purpose

We aimed to investigate the distribution of ocular residual astigmatism (ORA) and its associations with age, gender, manifest refraction, and other ocular indicators in Chinese patients with myopia.

Design

This is a multi-center retrospective cross-sectional study.

Method

The study included 7,893 patients with myopia (7,893 eyes) aged 18–40 years from five ophthalmic centers. Anterior segment biometrics of the eyes were collected from the Pentacam. ORA and its summated vector mean were calculated using Alpins vector analysis. Compensation factor (CF) was used to evaluate the relation between ORA and corneal astigmatism. ORA in different age, gender, and refraction groups was compared. The Spearman correlation was adopted to reveal multiple ocular indicators associated with ORA, which were integrated into a multiple linear regression model to predict ORA.

Results

Distribution of ORA was slightly positively skewed (Skewness= 2.111, Kurtosis = 19.660, KS P < 0.0001). Mean ORA was 0.74 ± 0.39 D (95% normal range: 0.14–1.54 D). Among all the subjects, 22.4% of the eyes had an ORA magnitude of 1.0 D or more. Undercompensation or full-compensation of anterior corneal astigmatism (ACA) by ORA prevailed in both J₀ (76.99%) and J₄₅ (58.48%). Women had higher ORA power than men (0.77 ± 0.36 D vs. 0.73 ± 0.41 D, P < 0.0001). Participants with less negative spherical equivalent (SE) or higher manifest astigmatism (MA) also had higher ORA (all P < 0.0001). ORA was significantly correlated with ACA (r = 0.405) and posterior corneal astigmatism (PCA, r = 0.356). The multivariate logistic regression analysis showed strong predictability of ORA magnitude >1.0 D using anterior segment parameters (area under the receiver operating characteristic curve: 0.739).

Conclusion

ORA is present in Chinese adults with myopia and is affected by multiple ocular factors. Our findings may provide valuable information about ORA distribution in candidates for refractive surgery, helping optimize the outcome of astigmatism correction.

Refractive development in individuals with ocular and oculocutaneous albinism

PURPOSE

Albinism is known to disrupt emmetropisation in animal models. However, it is not clear if the same effect is seen in humans. This study aimed to investigate the refractive profile in individuals diagnosed with ocular albinism (OA) and oculocutaneous albinism (OCA) based on a large dataset.

METHODS

Required data from 618 individuals (61% males and 39% females) diagnosed with albinism were exported from the eyeSmart electronic medical records of L V Prasad Eye Institute. Overall, there were 112 (18%) individuals diagnosed with OA and 506 (82%) with OCA. Based on the spherical equivalent refraction (SER), individuals were classified as emmetropes, myopes, and hyperopes.

RESULTS

The overall spherical equivalent refraction of the individuals ranged from -25.00D to + 12.00D with a median + 0.25D (-2.00 to + 2.25 D). The proportion of individuals with albinism (combined OA, OCA) having hyperopia and myopia (overall: N = 282;45.6% vs. N = 245;39.6%) were similar (p = 0.18), and the least were with emmetropia (overall: N = 91;14.7%). Across all the age groups (0-10, 11-20, 21-30, > 30 years), the frequency of hyperopes and myopes was significantly higher (p < 0.05) compared to emmetropes. Both high degrees of hyperopia and myopia were found in individuals diagnosed with OA and OCA. Irrespective of the albinism type, with-the-rule (70%) astigmatism was the most prevalent compared to other types of astigmatism. The frequency of with-the-rule astigmatism was significantly high in the presence of nystagmus compared to individuals with no nystagmus in both OA (75% vs 25%, p = 0.01) and OCA (77% vs 23%, p = 0.014) groups.

CONCLUSION

The presence of both high hyperopia and high myopia and very few numbers with emmetropia across all age groups indicates disrupted normal refractive development in individuals with albinism. With-the-rule astigmatism and nystagmus may result in meridional degradation of the retinal image leading to impairment of normal emmetropisation process in individuals with albinism.

Prevalence of and factors associated with astigmatism in preschool children in Wuxi City, China

PURPOSE

To investigate the status of astigmatism in preschool children in Wuxi City, and explore the risk factors related to astigmatism. The risk factors related to astigmatism development as predictors can help us identify preschool children who need vision screening at an early stage to ensure good visual quality.

METHODS

The cross-sectional study was conducted in 10 kindergartens randomly selected in five districts of Wuxi City in November 2018. All preschool children were measured by objective refractometry under non-cycloplegic refraction. The basic information of preschool children was collected. The relevant factors of astigmatism in the questionnaire were completed by parents. Spss 26. 0 software was used for univariate and multivariate correlation analysis.

RESULTS

A total of 889 preschool children participated in the study, 864 were finally included in the study. The prevalence of astigmatism was 36.0%. The risk of astigmatism in premature children was higher than that in non-premature children (adjusted odds ratio = 1.841). The prevalence of astigmatism with parents' astigmatism history was higher, compared with preschool children without parents' astigmatism history (adjusted odds ratio = 2.037). When maternal age at childbirth was older (≥ 35 years old), the risk of astigmatism increased in preschool children (adjusted odds ratio = 2.181). Compared with bottle feeding, the risk of astigmatism for mixed feeding and breastfeeding reduced in preschool children. Compared with preschool children exposed to electronic screen for less than 2 h every day, preschool children exposed to electronic screen for more than 2 h had an increased risk of astigmatism (P = 0.004).

CONCLUSION

The prevalence of astigmatism among preschool children in Wuxi City was high. Some risk factors such as premature birth, parents' astigmatism history, maternal age at childbirth, feeding pattern, and electronic screen exposure time were closely related to the occurrence of astigmatism among preschool children. For preschool children with significant risk factors, their eyesight should be checked regularly to ensure their visual quality.

Impact of unintended initial dissection of the posterior plane during SMILE surgery on surgery time and visual outcomes

BACKGROUND

To study the impact of unintended initial dissection of the posterior plane (UIDPP) on operation time and surgical outcomes during small incision lenticule extraction (SMILE) surgery.

METHODS

This was a retrospective study. Based on the SMILE procedure video, the operating eyes were assigned to the normal and UIDPP groups according to the presence or absence of UIDPP signals during surgery. The UIDPP group was further separated into early and late detection based on whether the complete dissection of the lenticule posterior plane or not. Patient's demographic data, preoperative evaluation data, operation time and postoperative outcomes were collected.

RESULTS

Sixty-six patients (66 eyes) who underwent SMILE were included, with 24 eyes with UIDPP (13 in the early detection group and 11 in the late group). The optical zone was smaller (median 6.5 vs. 6.6, P = 0.007), and the operation time was longer (median, 189.5 vs. 91.0 s, P < 0.001) in the UIDPP group compared with normal group. There were significant differences in operation time between the late detection group and early detection group (median, 489.0 vs. 139.0 s, P < 0.05) and between the late detection group and normal group (median 489.0 vs. 91.0 s, P < 0.05), while the optical zone was different only between the late detection and normal groups (median, 6.5 vs. 6.6, P < 0.05). At the one-year follow-up, UDVA was better than or equal to 20/20 in 87.5% of eyes, and 75% of eyes were within ± 0.5 D of the intended refractive target. One eye lost one Snellen line.

CONCLUSION

The occurrence of UIDPP will significantly prolong the operation time, but not affect the recovery of long-term visual acuity after surgery. Detecting UIDPP earlier could help shorten the operation time.

Ophthalmological findings in children with unicoronal craniosynostosis

INTRODUCTION

Among non-syndromic, single-suture craniosynostoses, unicoronal craniosynostosis (UCS) presents the highest rate of ophthalmic manifestations requiring a visual follow-up, due to the high risk of amblyopia. After birth or during childhood, children with UCS have a high risk to present an aniso-astigmatism and a strabismus. The aim of this study was to characterize clinical ophthalmologic findings associated with UCS in a paediatric cohort.

METHODS

This retrospective study included children admitted in our unit between 2015 and 2021, with isolated UCS treated in our institution and complete ophthalmological assessment comprising visual assessment, refractive status and oculomotor examination. Children with associated craniofacial disorders were excluded.

RESULTS

A total of 28 children met the inclusion criteria. Median age was 62 [13-192] months with a large proportion of girls (86%) and 71% of right-sided UCS. The mean best corrected visual acuity was 0.07 (±0.13) LogMAR, including 10 (36%) children with an amblyopia or history of amblyopia. Astigmatism was significantly higher on the contralateral side of the UCS than on the ipsilateral side, with a refractive cylinder error of 0.97 (±1.06) vs 0.56 (±0.68) diopters, respectively (p = 0.03). Strabismus was observed in 20 patients (71%) with a main pattern of esotropia with a vertical component. A pseudo-superior oblique palsy was found in 13 children (65%) with a median cyclodeviation of 8.7° [-5,4°-20.6°].

CONCLUSION

Children with UCS experience a high rate of various visual manifestations. This study highlights their need for a strict ophthalmological follow-up, in order to early diagnose and prevent visual complications.

Prevalence of myopia among urban and suburban school children in Tamil Nadu, South India: findings from the Sankara Nethralaya Tamil Nadu Essilor Myopia (STEM) Study

PURPOSE

To report the baseline prevalence of myopia among school children in Tamil Nadu, South India from a prospective cohort study.

METHODS

Children between the ages of 5 and 16 years from 11 schools in two districts of Tamil Nadu underwent vision screening. All children underwent visual acuity assessment using a Pocket Vision Screener followed by non-cycloplegic open-field autorefraction (Grand Seiko WAM-5500). Myopia was defined as a spherical equivalent (SE) refraction of ≤-0.75 D and high myopia was defined as SE ≤ -6.00 D. Distribution of refraction, biometry and factors associated with prevalence of myopia were the outcome measures.

RESULTS

A total of 14,699 children completed vision screening, with 2% (357) of them having ocular abnormalities other than refractive errors or poor vision despite spectacle correction. The remaining 14,342 children (7557 boys; 52.69%) had a mean age of 10.2 (Standard Deviation [SD] 2.8) years. A total of 2502 had myopia in at least one eye, a prevalence of 17.5% (95% CI: 14.7-20.5%), and 74 (0.5%; 95% CI: 0.3-0.9%) had high myopia. Myopia prevalence increased with age (p < 0.001), but sex was not associated with myopia prevalence (p = 0.24). Mean axial length (AL; 23.08 (SD = 0.91) mm) and mean anterior chamber depth (ACD; 3.45 (SD = 0.27) mm) positively correlated with age (p < 0.001). The mean flat (K1; 43.37 (SD = 1.49) D) and steep (K2; 44.50 (SD = 1.58) D) corneal curvatures showed negative correlation with age (p = 0.02 and p < 0.001, respectively). In the multivariable logistic regression, older age and urban school location had higher odds for prevalence of myopia.

CONCLUSION

The baseline prevalence of myopia among 5- to 16-year-old children in South India is larger than that found in previous studies, indicating that myopia is becoming a major public health problem in this country.

The prevalence of refractive error in schoolchildren

CLINICAL RELEVANCE

Information on the refractive error prevalence in school-aged children will result in delivering the optimal eye health service to this group.

BACKGROUND

Understanding the prevalence of refractive error in school-aged children is crucial to reduce the consequences of uncorrected refractive error. This study aims to investigate the prevalence of refractive error among school-aged children in Shiraz, Iran.

METHODS

In this cross-sectional population-based study, 2001 schoolchildren aged 6-12 years participated. All participants underwent cycloplegic refraction. Spherical equivalent (SE) of -0.50 dioptre or more was considered as myopia, SE of +2.00 dioptre or more as hyperopia, and astigmatism as cylinder power of 0.75 dioptre or more. The difference of 1.00 dioptre or more between two eyes defined as anisometropia.

RESULTS

The prevalence of myopia was 11.6% (95% confidence interval [CI]: 10.2-13.1%), hyperopia 6.7% (95%CI: 5.6-7.9%), and astigmatism 28.9% (95%CI: 26.9-31.0%), out of which 82.1% had with the rule astigmatism. Anisometropia was detected in 4.0% (95%CI: 3.2-5.0%) of children. Astigmatism and anisometropia were significantly higher in boys (p < 0.001, p = 0.03 respectively). The SE decreased significantly with increasing age (p < 0.001) indicating an increase in myopia with age. In addition, the rate of myopic astigmatism increased with age (p < 0.001). Among studied schoolchildren 97.0% could achieve the best-corrected visual acuity of 6/6 and 3.0% could not in the better eye.

CONCLUSION

Astigmatism was the most common refractive error among primary school children. The prevalence of myopia was relatively higher than other studies conducted in Iran, and it increased with age. These results may highlight the role of lifestyle changes and increased near work activities on the myopic shift in school-aged children. The findings provide information for screening programmes in school-aged children.

Prevalence of refractive errors among school students in Ethiopia: A systematic review and meta-analysis

Objective:

Refractive errors are most common ocular disorders among children and adolescents. They remain as secondary causes of avoidable blindness in impoverished areas in Africa, most notably in Ethiopia. The problem worsens if it is not managed and addressed early. The aim of this systematic review and meta-analysis was to determine the prevalence of refractive errors among school students in Ethiopia.

Methods:

We searched international databases such as PubMed/Medline, Web of Science, CINAHL, Embase, Scopus, Cochrane Library, Google Scholar, and Science Direct for relevant articles. Data were extracted using Microsoft Excel and exported to Stata version 14.0 software for analysis. The Cochrane Q and I2 tests were used to assess heterogeneity. Funnel plot, Egger’s, and Begg’s tests were used to assess reporting bias. Random effect meta-analysis model was employed to estimate pooled prevalence of refractive errors. A regional subgroup analysis was carried out.

Results:

We reviewed 22 qualified studies with 23,355 study participants. The overall prevalence of refractive errors among school students was 7.36% (95% confidence interval = 6.05, 8.67). The prevalence of myopia, hyperopia, and astigmatism was 5.10% (95% confidence interval = 3.79, 6.40), 0.95% (95% confidence interval = 0.59, 1.31), and 0.01% (95% confidence interval = 0.01, 0.04), respectively. From subgroup analysis, the highest prevalence of refractive errors was reported in Amhara Region (9.18%, 95% confidence interval = 6.63, 11.74), followed by Southern Nations, Nationalities, and Peoples’ region (6.78%, 95% confidence interval = 4.65, 8.92) while the lowest prevalence of refractive errors was reported in Addis Ababa (3.93%, 95% confidence interval = 3.30, 4.56).

Conclusion:

In Ethiopia, the prevalence of refractive errors among school students is higher (7.36%) compared to what it was 5 years (7.05%) ago. Amhara Region has the highest prevalence of refractive errors among school students in Ethiopia with myopia being the most common type of refractive error.

Refractive errors and risk factors for myopia in infants aged 1-18 months in Tianjin, China

BACKGROUND

Infancy is the of a child's visual development. Refractive errors, especially myopia, are a common vision disorder. Thus, the purpose of this study was to explore refractive errors and risk factors for myopia among infants aged 1-18 months in Tianjin, China.

METHODS

A total of 583 infants aged 1-18 months participated in this cross-sectional study at Tianjin Women's and Children's Health Center in China from February 2019 to November 2020. Each infant received a complete ophthalmologic examination, and myopia-related risk factors were investigated using a questionnaire.

RESULTS

A total of 583 eligible infants participated in this study, including 312 (53.5%) boys and 271 (46.5%) girls. There were 164 (28.1%) premature born infants. The mean age was 6.59 ± 4.84 months (range, 1-18 months). The mean spherical equivalent (MSE) for the right eye was 1.81 D ± 1.56 D, with no difference related to sex (P = 0.104). Refractive state showed an average hyperopia of +2.74 ± 1.74 D at early ages, followed by a trend toward less hyperopia, finally reaching +1.35 ± 1.44 D at the age of 18 months (P ≤0.001). The overall prevalence rates of myopia (MSE ≤ -0.50 D), emmetropia (-0.50 D<MSE<+0.50 D), hyperopia (MSE ≥ +2.00 D), and astigmatism (≥ 1.50 D) were 5.1%, 10.8%, 42.7%, and 49.9%, respectively. The chi-square tests showed that gender, gestational age ≥37 weeks, winter birth, prenatal exposure to environmental tobacco smoke, and parental history of high myopia were associated with children's myopia (P = 0.022, P = 0.023, P = 0.038, P = 0.015, P<0.001, respectively).

CONCLUSIONS

Among Chinese infants in Tianjin, hyperopia and astigmatism were the most frequent refractive errors, and the diopter was lower in individuals with higher age. In a small number of infants with myopia, genetic factors and the prenatal environment were associated with the early onset of myopia.

Ocular findings in 22q11.2 deletion syndrome: A systematic literature review and results of a Dutch multicenter study

The 22q11.2 deletion syndrome (22q11.2DS) is a multisystem disorder with an estimated prevalence of 1:3000 live births. Manifestations show a marked variability in expression and include speech‐ and language delay, intellectual disability, and neuropsychiatric disorders. We aim to provide an overview of ocular findings in 22q11.2DS in order to optimize recommendations for ophthalmic screening. We combined results from a systematic literature review with results from a multicenter cross‐sectional study of patients with 22q11.2DS who were assessed by an ophthalmologist. Our systematic literature search yielded four articles, describing 270 patients. We included 132 patients in our cross‐sectional study (median age 8.9 [range 0–56] years). Most reported ocular findings were retinal vascular tortuosity (32%–78%), posterior embryotoxon (22%–50%), eye lid hooding (20%–67%), strabismus (12%–36%), amblyopia (2%–11%), ptosis (4%–6%), and refractive errors, of which hyperopia (6%–48%) and astigmatism (3%–23%) were most common. Visual acuity was (near) normal in most patients (91%–94%). Refractive errors, strabismus, and amblyopia are treatable conditions that are frequently present in patients with 22q11.2DS and should be corrected at an early stage. Therefore, in 22q11.2DS, we recommend ophthalmic and orthoptic screening at the age of 3 years or at diagnosis, and a low‐threshold referral in adults.

Global disease burden of uncorrected refractive error among adolescents from 1990 to 2019

Background

To estimate the global disease burden of uncorrected refractive error (URE) among adolescents and assess the contributions of various risk factors to disability-adjusted life-years (DALYs) due to URE.

Methods

Global, regional and country-level DALY numbers and rates due to URE among adolescents were acquired from the Global Burden of Disease Study 2019 database. Human Development Index (HDI), Socio-Demographic Index (SDI) and other country-level data were obtained from other open databases as potential indicators. Regression analysis was used to evaluate associations between DALY rates among adolescents and potential predictors.

Results

Global DALYs due to URE among adolescents rose by 8% between 1990 and 2019 but moderately decreased by 4.8% during this period after adjusting for population size. Female adolescents showed higher DALY rates. DALY rates sharply increased from 5 to 9 years of age, then rose more slowly, reaching a plateau before 20 years of age. Country-level DALY rates in 2019 were positively associated with HDI, SDI, and urbanization rates but negatively correlated with primary school dropout rates. Higher disease burden of adolescents visually impaired from URE was associated with lower primary school dropout rates (β = − 0.257, 95% CI − 0.376 to − 0.138, P < 0.001) and higher urbanization rates (β = 0.257, 95% CI 0.067 to 0.256, P = 0.001).

Conclusions

Higher socioeconomic status, urbanization rates and education levels are associated with a heavier disease burden of URE among adolescents. The findings of this study can provide a reference for policy making on resource allocation for URE prevention and control in teenagers.

Ocular manifestations of Beckwith-Wiedemann syndrome

Beckwith-Wiedemann syndrome (BWS; OMIM #130650) is a pediatric overgrowth disorder with few known ocular manifestations. We retrospectively reviewed the medical records of patients with BWS evaluated at Bascom Palmer Eye Institute over a 10-year period and identified 5 patients, of whom 4 presented with ocular misalignment and 1 with eye rubbing. Three patients were noted to have strabismus, and 1 patient manifested with significant astigmatism. No patients received surgical intervention.

Gender and age distribution of refractive errors in an optometric clinical population

AIM

To determine the patterns of distribution of refractive errors in a clinical sample of patients examined in an optometry practice.

METHOD

In this retrospective study, the clinic records of 6687 patients aged 6 to 85 years comprising 2168 (32.2%) males and 4519 (67.5%) females were reviewed. Refractive error were analysed according to gender, age, as well as types and categories including axis of astigmatism using the vector power analysis method where the traditional sphero-cylinder was transformed into J0 (primary) and J45 (oblique) astigmatic components.

RESULTS

Only the analysis for right eye was reported as right and left spherical equivalent were similar. The mean with standard deviations for refractive errors were: Myopia: -1.95 ± 2.6, hyperopia: 1.04  ± 0.9, astigmatism: -1.22 ± 0.71 and anisometropia: -0.01 ± 2.5 DS. The distributions with significant changes included males that were significantly more myopic and astigmatic, while females were more hyperopic across the age groups. Furthermore, myopia decreased, while hyperopia, astigmatism and anisometropia increased with increasing age. Unique findings from this study include: myopia peaked earlier, second hyperopic shift commenced after age 82 years and the distribution of severity of astigmatism contrasts with previous understanding.

CONCLUSION

Although the patterns of distribution of refractive errors in patients aged 6 to 85 years corroborates previous findings, myopia and hyperopia peak, as well as severity of astigmatism were unique to the present study. Results from non-clinic populations will be useful to confirm trends reported in this study.

Meridional Anisotropy of Foveal and Peripheral Resolution Acuity in Adults With Emmetropia, Myopia, and Astigmatism

Purpose

To quantify astigmatism-related meridional anisotropy in visual resolution at central, nasal, and inferior visual fields.

Methods

Three groups of young adults (range, 18–30 years) with corrected-to-normal visual acuity (logMAR 0) were recruited: (1) myopic astigmats (MA): spherical-equivalent error (SE) < −0.75D, with-the-rule astigmatism ≥ 2.00D, n = 19; (2) simple myopes (SM): SE < −0.75D, astigmatism ≤ 0.50D, n = 20; and (3) emmetropes (EM): SE ± 0.50D, astigmatism ≤ 0.50D, n = 14. Resolution acuity was measured for the horizontal and vertical gratings at central and peripheral visual fields (eccentricity: 15°) using a 3-down 1-up staircase paradigm. On- and off-axis refractive errors were corrected by ophthalmic lenses.

Results

The MA group exhibited meridional anisotropy preferring vertical gratings. At the central field, the MA group had better resolution acuity for vertical than horizontal gratings, and their resolution acuity for horizontal gratings was significantly worse than the SM and EM groups. At peripheral visual fields, both the SM and EM groups showed better resolution acuity for the radial (i.e., nasal field: horizontal gratings; inferior field: vertical gratings) than tangential orientation. However, the MA group tended to have better resolution acuity for the tangential orientation (i.e., vertical gratings), and their resolution acuity for horizontal gratings was significantly lower than the SM and EM groups at the nasal field. No significant differences were found in the inferior field among the three groups.

Conclusions

This study provided evidence of astigmatism-related meridional anisotropy at the fovea and nasal visual fields, underscoring the significant impact of astigmatism on orientation-dependent visual functions.

Proposing an ensemble learning model based on neural network and fuzzy system for keratoconus diagnosis based on Pentacam measurements

PURPOSE

The present study was done to evaluate efficiency of an ensemble learning structure for automatic keratoconus diagnosis and to categorize eyes into four different groups based on a combination of 19 parameters obtained from Pentacam measurements.

METHODS

Pentacam data from 450 eyes were enrolled in the study. Eyes were separated into training, validation, and testing sets. An ensemble system was used to analyze corneal measurements and categorize the eyes into four groups. The ensemble system was trained to consider indices from both anterior and posterior corneal surfaces. Efficiency of the ensemble system was evaluated and compared in each group.

RESULTS

The best accuracy was achieved by the ensemble system with both multilayer perceptron and neuro-fuzzy system classifiers alongside the Naïve Bayes combination method. The accuracy achieved in KC versus N distinction task was equal to 98.2% with 99.1% of sensitivity and 96.2% of specificity for KC detection. The global accuracy was equal to 98.2% for classification of 4 groups, with an average sensitivity of 98.5% and specificity of 99.4%.

CONCLUSION

In this study, authority of an ensemble learning system to work out intricate problems was presented. Despite using fewer parameters, herein, comparable or, in some cases, better results were obtained than methods reported in the literature. The proposed method demonstrated very good accuracy in discriminating between normal eyes and different stages of keratoconus eyes. In some cases, it was not possible to directly compare our results with the literature, due to differences in definitions of KC group as well as differences in selection of items and parameters.

Clinical Outcomes of Small Incision Lenticule Extraction in Myopia: Study of Vector Parameters and Corneal Aberrations

PURPOSE

To investigate clinical outcomes of small incision lenticule extraction (SMILE) including vector parameters and corneal aberrations in myopic patients.

METHODS

This retrospective, observational case series included 57 eyes (29 patients) that received treatment for myopia using SMILE. Visual acuity measurement, manifest refraction, slit-lamp examination, autokeratometry, corneal topography, and evaluation of corneal wavefront aberration were performed preoperatively and at 1 and 3 months after surgery. We analyzed the safety, efficacy, vector parameters, and corneal aberrations at 3 months after surgery.

RESULTS

Preoperatively, mean manifest refraction spherical equivalent refraction was -4.94 ± 1.94 D (range, -8.25 to 0 diopters [D]), and the cylinder was -1.14 ± 0.82 D (range, -3 to 0 D). Mean manifest refraction spherical equivalent improved to -0.10 ± 0.23 D at 3 months postoperatively, when uncorrected distance visual acuity was 20 / 20 or better in 55 (96%) eyes. The linear regression model of target induced astigmatism vector versus surgically induced astigmatism vector exhibited slopes and coefficients (R²) of 0.9618 and 0.9748, respectively (y = 0.9618x + 0.0006, R² = 0.9748). While total corneal root mean square higher order aberrations, coma and trefoil showed statistically significant increase, spherical aberration did not show statistically significant change after SMILE.

CONCLUSIONS

SMILE has proven to be effective and safe for correcting myopia and astigmatism. We showed that SMILE did not induce spherical aberrations. A small increase in postoperative corneal higher order aberration may be associated with increase in coma and trefoil.

Association between greater residential greenness and decreased risk of preschool myopia and astigmatism

OBJECTIVE

Rapid urbanization has led to reduced greenness in many areas, this has been linked to adverse health outcomes. The aim was to determine the association between residential greenness experienced during very early childhood with preschool myopia and astigmatism and to explore the potential mediating role of screen time on any associations.

METHOD

Information regarding socio-demographic characteristics, home address, screen time during early childhood, and refraction data from vision screenings of 53,575 preschoolers from Longhua Child Cohort Study were collected via questionnaires. Residential greenness was calculated as the average of satellite-derived Normalized Difference Vegetation Index in buffers of 100, 250, and 500 m around each child's home address. Logistic and linear regression models were used to examine the relationships between residential greenness, screen time, and preschool myopia and astigmatism.

RESULT

The mean (SD) age of the 53,575 preschoolers was 5.0 (0.7) years, and 24,849 (46.4%) were girls. A total of 1236 (2.3%) preschoolers had myopia and 5347 (10.0%) had astigmatism. In the adjusted model, a higher neighborhood greenness level within 100 m buffers around the home address was associated with decreased risk of myopia (adjusted odds ratios (AOR): 0.62, 95% confidence interval (CI): 0.38-0.99), and higher neighborhood greenness levels within 100, 250, and 500 m decreased the risk of astigmatism, and their AORs (95% CIs) were 0.55 (0.43-0.70) for 100 m, 0.59 (0.41-0.83) for 250 m, 0.61 (0.42-0.90) for 500 m, respectively. Greater screen time during early childhood increased the risk of myopia (AOR = 1.33) and astigmatism (AOR = 1.23). Reduction in screen time fully mediated the benefits of greater residential greenness on preschool myopia, but partially mediated that on preschool astigmatism (p < 0.05).

CONCLUSION

Higher residential greenness reduces the risk of preschool myopia and astigmatism; the benefits of residential greenness were mediated through reduced daily screen time.

Cycloplegic Effects on the Cylindrical Components of the Refraction

It is important to predict which astigmatic patients require separate refraction for near vision. This study compared cylindrical components changes by cyclopentolate 1% for the low and high amount of astigmatism. The right eyes of 1014 healthy individuals (307 males and 707 females) with cylindrical refractive power more than -0.5 diopter on autorefractometer were selected. Both male and female patients in the age range of 17-45 years were refracted before and after cycloplegia, using 1% cyclopentolate. All volunteers were classified into 2 subgroups including the lower astigmatism group (-2.25 to -0.50) and the higher astigmatic group (-2.50 to over). Alpines' method was used to compare the effect of cycloplegic drop on cylindrical power. The mean age in the lower astigmatism group (29.58; 95% CI: 29.18 to 29.99 years) was not significantly different from the higher astigmatic group (29.85; 95% CI: 29.07 to 30.62) and there were no significant differences in gender between these two groups (P=0.54). Differences between wet and dry refraction in J0 (-0.03; 95% CI:-0.06 to -0.008) and J45 (-0.03; 95% CI:-0.06 to -0.01) were significant only in the higher astigmatic group. Axis changes by the cycloplegic drop in the lower astigmatism group were 3.51 (CI: 3.22 to 3.81) and axis changes by the cycloplegic drop in the higher astigmatism group were 2.21 (CI: 1.73 to 2.49). In patients with a lower amount of astigmatism (-2.25 to -0.50), additional near subjective refraction could be done for precise determination of axis and in patients with a higher amount of astigmatism (-2.50 to over), near subjective refraction might be done for precise determination of power.