The prevalence of anisometropia, amblyopia and strabismus in schoolchildren of Shiraz, Iran

Prevalence of anisometropia and its associated factors in school-age children

PURPOSE

To determine the prevalence of anisometropia and the associated demographic and biometric risk factors in children.

METHODS

This cross-sectional study was conducted on the elementary school children of Shahroud, east of Iran, in 2015. All rural students were recruited, while multistage cluster sampling was used to select the students in urban areas. All children underwent optometric examinations including the measurement of uncorrected and corrected visual acuity, autorefraction, and subjective refraction with cycloplegia. Biometric components were measured using the Allegro Biograph. Myopia and hyperopia were defined as a spherical equivalent ≤-0.5 and ≥ +2.00 diopter, respectively. Students with a history of ocular trauma or lack of cycloplegic refraction at least in one eye were excluded from the study.

RESULTS

Of 6624 selected children, 5620 participated in the study. After applying the exclusion criteria, the data of 5357 students (boys: 52.8%, n = 2834) were analyzed. The mean age of the subjects was 9.2 ± 1.7 years (range: 6-12 years). The prevalence of anisometropia ≥ 1 D was 1.1% (95% CI: 0.8 to 1.4) in all children, 1.0% (95% CI: 0.7-1.3) in boys, 1.3% (95% CI: 0.8-1.7) in girls, 1.1% (95% CI: 0.8-1.4) in urban children, and 1.4% (95% CI: 0.5-2.3) in rural children. The prevalence of anisometropia was 8.8% (95% CI: 5.3-12.2) in myopic and 5.7% (95% CI: 2.8-8.5) in hyperopic children. Axial length asymmetry (OR = 40.9; 95%CI: 10.2-164.1), myopia (OR = 17.9; 95% CI: 9.4-33.9), and hyperopia (OR = 10.1; 95% CI: (5.1-19.7) were associated with anisometropia in multiple logistic regression model. More anisometropia was associated with more severe amblyopia. The odds of amblyopia (OR = 82.3: 38.2-177-3) and strabismus (OR = 17.6: 5.5-56.4) were significantly higher in anisometropic children. The prevalence of amblyopia was 21.7% in children with myopic anisometropia ≥ 3D, 66.7% in children with hyperopic anisometropia ≥ 3D, and 100% in cases with antimetropia ≥ 3D.

CONCLUSION

The prevalence of anisometropia was low in Iranian school children. However, a high percentage of anisometropic students had amblyopia and strabismus. Axial length was the most important biometric component associated with anisometropia.

Temporal trend of anisometropia incidence in Chinese school-aged children before and during the COVID-19 pandemic

Objective

To analyze and compare the temporal trends in the incidence of anisometropia among Chinese school-aged children both before and during the COVID-19 pandemic, and to investigate the impact of the pandemic on the incidence of anisometropia.

Methods

We conducted a retrospective study comprising six distinct and independent longitudinal cohorts, each including children aged 6 to 13 years who visited the Joint Shantou International Eye Center between January 2010 and December 2021. Children were grouped into cohorts based on the year of their first eye clinic visit: 2010, 2012, 2014, 2016, 2018, or 2020. Only children without anisometropia at initial visits, followed for 18 ± 6 months, were included. The cumulative incidence and risk factors of anisometropia were analyzed using Kaplan-Meier estimation and Cox proportional hazards regression models. Subgroup analyses were performed based on sex, age groups, initial refractive error status, and initial interocular SE difference. Anisometropic children were further categorized into myopic and non-myopic, with subsequent subgroup analyses conducted.

Results

Of 11,235 children were recruited from six cohorts (2010: n = 1,366; 2012: n = 1,708; 2014: n = 1,896; 2016: n = 2,354; 2018: n = 2,514; 2020: n = 1,397), 869 children developed anisometropia during a mean follow-up of 17.5 ± 3.7 months. After adjustment of confounding factors, we found that the risk of anisometropia remained relatively stable before 2020 but significantly increased in the 2020 cohort (adjusted HR 2.93, 95% CI 2.23 to 3.86; p < 0.001). This trend persisted in studies of spherical anisometropia (adjusted HR 2.52, 95% CI 1.60 to 3.97; p < 0.001) and cylindrical anisometropia (adjusted HR 2.91, 95% CI 1.69 to 3.62; p < 0.001). Older age and a greater initial difference in SE between the two eyes were also significantly associated with a higher risk of developing anisometropia (p < 0.001). Subgroup analyses consistently showed increased risk in the 2020 cohort.

Conclusion

This study reveals a concerning rise in anisometropia incidence among Chinese school-aged children during the period of the COVID-19 pandemic. These findings highlight the worrisome rise in anisometropia risk during the COVID-19 pandemic and emphasize the importance of early detection and management to safeguard children's visual health.

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.

Evaluation of visual functions in Iranian hypothyroid adults

INTRODUCTION

The aim of this study was to investigate the effects of hypothyroidism on visual functions such as visual acuity, refractive errors, colour vision, and contrast sensitivity, among hypothyroid adults.

METHODS

Forty-three patients with clinical hypothyroidism along with 43 age- and sex-matched healthy individuals underwent visual examinations, including visual acuity, refractive errors, eye deviations with the cover test, colour vision with the D15 test, and contrast sensitivity with Pelli-Robson test.

RESULTS

It was indicated that visual acuity, refractive errors, phoria, and colour vision had no significant difference between the hypothyroid and control groups. Contrast sensitivity decreased in hypothyroid subjects as compared with controls. The mean values of binocular contrast sensitivity were 1.85 ± 0.09 log in the hypothyroid group and 1.93 ± 0.09 log in controls, which showed a statistically significant difference (p = .03).

CONCLUSIONS

Our findings illustrated a reduced contrast sensitivity in adult hypothyroidism. Since CS is related to functioning and quality of life, a comprehensive and detailed eye examination may be beneficial for hypothyroidism patients.

Efficacy and safety of traditional Chinese medicine decoction in the treatment of adolescent myopia: A protocol for systematic review and network meta-analysis

BACKGROUND

Adolescent myopia has become a major public health problem in Asian countries and even the world. Due to its unstable prognosis and numerous complications, it has caused serious social and economic burden. As a common treatment in Asia, Chinese medicine has been shown to be effective in controlling the development of myopia, but its evidence-based medical evidence is not sufficient. Therefore, the purpose of this study is to evaluate the efficacy and safety of traditional Chinese medicine (TCM) in the treatment of adolescent myopia through network meta-analysis, and to provide evidence for clinical and scientific research.

METHODS

We searched seven databases for randomized controlled trials of TCM decoction for adolescent myopia, including PubMed, the Cochrane Library, EMbase, China National Knowledge Infrastructure, China Biological Medicine, Chinese Scientific Journals Database, and wan-fang databases, from the date of the establishment of each database to January 31, 2022. The network meta-analysis will be implemented through Aggregate Data Drug Information System 1.16.8 and Stata 13.0 software. Primary outcomes include distant vision, intraocular pressure, and diopter. Mean differences or odds ratios will be used for statistical analysis. We will ensure the reliability of the results through node-split model and heterogeneity analysis. In addition, the Cochrane Collaboration's tool and Grading of Recommendations Assessment, Development and Evaluation system will be used for the methodological quality and the evidence quality.

RESULTS

This study will provide reliable evidence for the clinical selection of TCM decoction in the treatment of adolescent myopia.

CONCLUSION

The results of this study will evaluate the efficacy and safety of TCM decoction in the treatment of adolescent myopia, and provide decision-making references for future clinical and scientific research.

ETHICS AND DISSEMINATION

This study did not require ethical approval. We will disseminate our findings by publishing results in a peer-reviewed journal.

OSF REGISTRATION NUMBER

DOI 10.17605/OSF.IO/VXQUP.

The Global Prevalence of Amblyopia in Children: A Systematic Review and Meta-Analysis

Epidemiological data about the prevalence of amblyopia around the world vary widely among regions and periods. This meta-analysis aimed to determine the global prevalence of amblyopia in children. PubMed, Embase, and the Cochrane Library were searched for prevalence studies published up to 5 November 2021. The outcome was the prevalence of amblyopia, analyzed as pooled estimates with 95% confidence intervals (CI). A total of 97 studies were included, including 4,645,274 children and 7,706 patients with amblyopia. The overall worldwide pooled prevalence of amblyopia was 1.36% (95%CI: 1.27-1.46%). The prevalence of amblyopia was higher in males (1.40%, 95%CI: 1.10-1.70%) than in females (1.24%, 95%CI: 0.94-1.54%) (OR = 0.885, 95%CI: 0.795-0.985, P = 0.025). The results of the meta-regression analysis showed that there were no significant associations between the prevalence of amblyopia and geographical area, publication year, age, sample size, and whether it was carried out in a developed or developing country (all P > 0.05). Begg's test (P = 0.065) and Egger's test (P < 0.001) showed that there was a significant publication bias in the prevalence of amblyopia. In conclusion, amblyopia is a significant vision problem worldwide, and public health strategies of early screening, treatment, and management are important.

Vessel Density and Retinal Thickness from Optical Coherence Tomography Angiography as New Indexes in Adolescent Myopia

Purpose

To evaluate and quantify blood perfusion and retinal thickness (RT) from the perspective of quadrants by optical coherence tomography angiography (OCTA) in adolescents with myopia and explore the relationship between axial elongation and related indexes of OCTA.

Methods

A total of 88 subjects (149 eyes) with different degrees of myopia were included in this cross-sectional study. Vessel density (VD) and RT of quadrants in macular and peripheral regions were measured through OCTA.

Results

The superficial VD (SVD) of the parainferior region was significantly correlated with axial length (AL) between the emmetropia (EM) group and high myopia (HI) group (P=0.012). There were significant differences in deep VD (DVD) in all quadrants, except for the foveal, perifoveal, and peri-inferior regions (P > 0.05). However, there were significant alterations in the whole, parainferior, and perinasal regions (P=0.030, 0.023, and 0.035) in the low-to-moderate myopia (L–M) group compared with those in the HI group. There were significant differences in the RT in all quadrants, except for the foveal, paratemporal, and paranasal regions (P > 0.05) between the EM and L–M groups and the foveal region (P > 0.05) between the EM and HI groups. Nevertheless, only RT in the peri-inferior region of the L–M and HI groups showed significant differences. AL was negatively correlated with SVD in the perifoveal and parainferior regions (r = −0.179, P=0.029; r = −0.227, P=0.005) and inversely correlated with DVD and RT in almost all quadrants, except for the foveal region (r = −0.020, P=0.811; r = 0.135, P=1.000).

Conclusion

DVD and RT were closely associated with the severity of myopia and might be new indexes in assessing and detecting myopia development via OCTA.

Prevalence of Strabismus and Its Associated Factors Among School-Age Children Living in Bahir Dar City: A Community-Based Cross-Sectional Study

INTRODUCTION

Strabismus is a manifest deviation of the eye that exceeds the control of the fusional mechanism so that the eyes are misaligned under binocular conditions. Its prevalence reaches from 0.7% to 5% globally and 1.5% to 17.9% in Ethiopia.

OBJECTIVE

This study aimed to assess the prevalence of strabismus and its associated factors among school-age children living in Bahir Dar city.

METHODS

A community-based cross-sectional study was conducted from April 15 to May 25, 2019, in Bahir Dar city and a total of 632 participants were recruited using a multistage sampling technique. The data were collected with a face-to-face interview, Snellen acuity, prisms, pen torch, portable slit lamp, and ophthalmoscope. The collected data were entered into Epi Info version 7 and transposed to statistical package for social science version 20 for formal statistical analysis. Frequency (percentage), mean (standard deviation), tables and graphs were used to present the summary statistics. All variables with a p-value of less than 0.2 in bi-variable logistic regression were entered into multiple logistic regression and variables with a p-value of less than 0.05 were taken as significantly associated with strabismus. The strength of association between variables was shown with an odds ratio and a 95% confidence interval.

RESULTS

A total of 611 children participated with a response rate of 96.7% and a mean age of 12.3 (±3.25). The prevalence of strabismus was 31 (5.0%), 95% CI: (3.45, 6.97). Family history of strabismus (AOR= 3.9 (95% CI: 1.71, 11.22)), hyperopia ≥ +3.00 diopters sphere (AOR=5.3 (95% CI: 2.01, 10.77)), and not with exclusive breastfeeding (AOR= 2.9 (95% CI: 1.14, 4.71)) were the only risk factors found for strabismus.

CONCLUSION

The prevalence of strabismus was 5% among children living in Bahr Dar city. A family history of strabismus, not with exclusive breastfeeding, and hyperopia ≥ +3.00 diopters sphere were associated with strabismus.

Assessment of Different Types of Strabismus Among Pediatric Patients in a Tertiary Hospital in Jeddah

Background Strabismus, also known as squint, is an ocular disorder in which the eyes do not align properly with each other when looking at an object. The estimated global prevalence of strabismus among children is between 1.3% and 5.7%. This study aimed to assess the various types of strabismus among pediatric patients in Jeddah, in the western region of Saudi Arabia. Methods The medical records of 281 patients with strabismus aged ≤18 years, who presented to the pediatric ophthalmology clinic in King Abdulaziz University Hospital between 2010 and 2019, were retrospectively reviewed. Data were analyzed using the Statistical Package for Social Sciences (SPSS; IBM Corp., Armonk, NY, USA). A p-value of 0.05 or less was considered statistically significant. Results Out of the 281 patients, 141 were (50.2%) female. The average age of the patients was 9.50 ± 4.24 years. The most common type of strabismus was esotropia (177 [63%] patients), followed by exotropia (96 [34.2%] patients), hypertropia (10 [3.6%] patients), and dissociated vertical deviation (four [1.4%] patients). Two-hundred thirty-one (82.8%) patients had bilateral strabismus. A total of 178 patients (63.3%) had no associated conditions with strabismus, whereas 103 (36.7%) had an associated condition. A significant relationship was observed between esotropia and prematurity (p = 0.024). Conclusion Esotropia was the most common type of strabismus among the patients, followed by exotropia. The results of this study showed that males were equally affected as females. We also found a significant relationship between esotropia and prematurity. Implementation of a compulsory nationwide pediatric ophthalmic screening program for children aged one, three, and five years is recommended to enable timely diagnosis of strabismus and any other refractive errors.

Eyes of Aniso-Axial Length Individuals Share Generally Similar Corneal Biometrics with Normal Eyes in Cataract Population

AIMS

To determine the characteristics of corneal biometrics in eyes from aniso-axial length cataract patients compared with eyes from non-aniso-axial length individuals.

METHODS

This is a retrospective case series. Cataract patients with preoperative binocular measurements were recruited. A binocular axial difference of ≥1 mm was considered to indicate aniso-axial length. The anterior segmental biometrics were measured using Pentacam HR (Oculus, Wetzlar, Germany) and IOLMaster 500 (Carl Zeiss Meditec, Jena, Germany). Comparisons of biometrics were made among 4 eye conditions: the longer eyes from aniso-axial length patients, the shorter eyes from aniso-axial length patients, the longer eyes from non-aniso-axial length patients, and the shorter eyes from non-aniso-axial length patients. The aniso-axial length eyes were also stratified into 8 subgroups with axial length (AL) increments of 1 mm, and the biometrics of the subgroups were compared.

RESULTS

There was smaller anterior corneal astigmatism in the shorter aniso-axial length group than those in the longer aniso-axial length group (1.01 ± 0.70 D vs 1.12 ± 0.76 D, P=0.031). The longer aniso-axial length eyes had greater anterior corneal steep curvature (44.13 ± 1.69 D vs 43.87 ± 1.69 D, P=0.009) and anterior corneal astigmatism (1.12 ± 0.76 D vs 1.02 ± 0.69 D, P=0.023) compared with longer non-aniso-axial length subjects. Other corneal biometrics were similar between the aniso-axial length eyes and the non-aniso-axial length eyes. In the longer aniso-axial length group, the posterior corneal aberrations of eyes in the ≥5 mm subgroups were greater than those in the <5 mm subgroups (0.879 ± 0.183 μm vs 0.768 ± 0.178 μm for total aberrations, P < 0.001; 0.228 ± 0.086 μm vs 0.196 ± 0.043 μm for high-order aberrations, P=0.036; 0.847 ± 0.173 μm vs 0.741 ± 0.179 μm for low-order aberrations, P=0.001).

CONCLUSION

Eyes of aniso-axial length individuals share generally similar corneal biometrics with normal eyes in cataract population. Anterior corneal astigmatism of the longer eyes from the aniso-axial length cataract patients was higher than that of the longer eyes from the non-aniso-axial length individuals. Total posterior corneal aberrations of the longer aniso-axial length eyes increased when the binocular axial difference was over 5 mm.

A systematic review of Amblyopia prevalence among the children of the world

Objective: to assess the prevalence of Amblyopia disease in the children of the world. Methods: In order to perform this systematic review, PICO was considered as the research question. Then, the preferred keywords were searched in Medline (via PubMed), Embase, Scopus, Web of Science, and ProQuest databases. The retrieved citations were reviewed by two independent inspectors in a three-step process in terms of the title, abstract, and full-text, based on the inclusion criteria. The studies included in the review were critically evaluated and then were extracted by two dependent expert reviewers. Finally, the prevalence of Amblyopia disease in the children of the world was pooled by meta-analysis CMA v.2 software. The heterogeneity of the selected studies was evaluated using I2 and chi-square. Also, subgroup-analysis was performed using designs and continents. Results: Out of 952 retrieved citations, 131 studies were included. The total prevalence of Amblyopia in the children of the world was calculated to be 4.3% [Pooled Prevalence: 4.3%, 95% CI: 2.6%-7.00%, P-value 0.0001]. In addition, the heterogeneity of the studies was reported to be high (Q: 48281.18, df: 56, p-value 0.001, I-square: 99.88). The subgroup analysis showed that America had the highest (5.57%, 95% CI: 2.23%-13.94%, P-value 0.0001) prevalence, and the lowest prevalence of Amblyopia in the children of the world was seen in Africa (7.1%, 95% CI: 0.003%-172.53%, P-value 0.05). Conclusion: It can be concluded that the total prevalence of Amblyopia is 3.4%, but this estimate varies in all continents, especially in Africa. The major reason for this variation was reported to be the heterogeneity of studies. These assessments have investigated different populations in terms of severity of illness, age, and gender. Therefore, further worldwide high-quality and valid studies should be carried out to allow the calculation of the real prevalence of Amblyopia among children of the world. Abbreviations: VA = visual acuity, ALSPAC = Avon Longitudinal Study of Parents and Children, JBI = Joanna Briggs Institute, PRISMA = Systematic Review and Meta-analysis, CMA = Comprehensive Meta-analysis Software.

National and sub national prevalence of Amblyopia and its trends from 1990 to 2018 in Iran

PURPOSE

To determine the national and subnational prevalence of amblyopia and the respective provincial distribution and trend during 1990-2018 in Iran.

METHODS

Amblyopia data retrieved from 26 original studies, systematic reviews, Data has been cleaned by STATA and a linear mixed effect spatio-temporal model was used to calculate Gaussian process regression mean functions. Using a Bayesian approach, by pooling empirical data based on the assumed prior, a posterior distribution obtained for age and sex specific prevalence prediction nationally during the study time and provincially.

RESULTS

The overall age-adjusted prevalence of Amblyopia was 0.03 (95% CI, 0.022-0.035). The prevalence was comparable in boys and girls (p = 0.85), highest prevalence was in >30 years old (p = 0.038). Our extrapolation revealed a stable trend of prevalence of Amblyopia in Iran during 1990-2018 (national screening program has been active from 1990 onwards). While Amblyopia prevalence suggested a declining trend in three provinces of Hormozgan, Qom and Tehran and it went up in 13 other provinces.

CONCLUSION

Amblyopia prevalence seems unchanged despite the concurrent screening program. It is noteworthy that the coverage of the program has been improved and has reached more than 85% in 2018. Our finding mandates a formal evaluation on the program.

Effect of Orthokeratology on Axial Length Elongation in Anisomyopic Children

SIGNIFICANCE

Anisomyopia is a natural experimental paradigm that compares dose response between fellow eyes. This study is the first to explore whether orthokeratology (ortho-k) has a dose-response effect on axial length growth and reduces the interocular difference in axial length in anisomyopic children.

PURPOSE

The purpose of this study was to compare the effect of ortho-k on axial length elongation between the fellow eyes of anisomyopic children.

METHODS

In this retrospective study, 49 anisomyopic children who wore ortho-k lenses were assigned to the anisomyopic ortho-k group. Based on the one-to-one match principle (same age and proximate spherical equivalent), high-isomyopic and low-isomyopic groups each enrolled 49 isomyopic children who wore ortho-k lenses with spherical equivalent similar to that of the more myopic eye and the less myopic eye in the anisomyopic ortho-k group, respectively. Forty-nine anisomyopic children who wore spectacles were enrolled in the anisomyopic spectacle group. At baseline and at 1- and 2-year visits, axial length was measured. Axial length elongation and interocular difference in axial length were compared.

RESULTS

In the anisomyopic ortho-k group, the less myopic eyes exhibited more axial length elongation than did the more myopic eyes during 1- and 2-year treatment periods (P < .01). However, there was no significant difference in axial length elongation between the fellow eyes in the isomyopic groups and anisomyopic spectacle group. At the 2-year visit, the interocular difference in axial length of children in the anisomyopic ortho-k group significantly decreased from 0.72 ± 0.34 to 0.56 ± 0.38 mm (P < .05). In contrast, ortho-k lens-wearing isomyopic children or spectacle-wearing anisomyopic children did not show a significant change in interocular difference in axial length.

CONCLUSIONS

Orthokeratology could reduce the amount of anisomyopia in children primarily through stronger myopia control in the more myopic eye.

Effects of orthokeratology lens on axial length elongation in unilateral myopia and bilateral myopia with anisometropia children

PURPOSE

To investigate the effect of orthokeratology (OK) lens on axial length (AL) elongation in unilateral myopia and bilateral myopia with anisometropia children.

METHODS

Twenty-seven unilateral myopia (group 1) and 25 bilateral myopia with anisometropia children (group 2) were involved in this 1-year retrospective study. The eyes with higher spherical equivalent refractive error (SER) were assigned to the H eyes subgroup and the fellow eyes with lower SER to the L eyes subgroup in the two groups.

RESULTS

The mean change in AL of H eyes and L eyes were 0.11 ± 0.19 mm, 0.30 ± 0.28 mm in group 1 (P = 0.04) and 0.09± 0.14mm, 0.13± 0.16mm in group 2 (P = 0.36), respectively. Multivariate regression analyses showed that significant difference of change in AL was found between H eyes and L eyes in group1 (β=0.25, P = 0.03), but no difference in group 2 (β=0.09, P = 0.12). The AL of H eyes in group 1 and group 2, H eyes in group 1 and L eyes in group 2 had the same increased rate (β= -0.04, P = 0.43; β = 0.02, P = 0.56).

CONCLUSIONS

Monocular OK lens is effective on suppression AL elongation of the myopic eyes and reduce anisometropia value in unilateral myopic children. The OK lens can control the AL elongation in both eyes at the same rate, but it cannot reduce anisometropia value in bilateral myopia with anisometropia children after 1-year follow-up.

Global prevalence of amblyopia and disease burden projections through 2040: a systematic review and meta-analysis

Purpose

Amblyopia is a leading cause of vision impairment among children and young adults. Individual studies showed significant variations in the prevalence of amblyopia in different regions and age groups. This study is to estimate the global prevalence of amblyopia by pooling its prevalence from the previous studies and to project the number of people affected through 2040.

Methods

We performed a systematic review and meta-analysis on the prevalence of amblyopia using data published before 20 October 2018. We estimated the prevalence rate of amblyopia and its 95% CI globally and by subgroups (eg, region and age). The prevalence data were applied to United Nations World Population Prospects to derive the projected number with amblyopia through 2040.

Results

A meta-analysis of 60 studies (1 859 327 subjects) showed that the pooled prevalence rate of amblyopia was 1.44% (95% CI 1.17% to 1.78%). Prevalences in Europe (2.90%) and North America (2.41%) were higher than in Asia (1.09%) and Africa (0.72%). The highest prevalence was found in subjects over 20 years old (3.29%). There was no difference in the prevalence between genders. We estimated 99.2 (95% CI 71.7 to 146.1) million people with amblyopia in 2019 worldwide, increasing to 175.2 (95% CI 81.3 to 307.8) million by 2030 and 221.9 (95% CI 83.7 to 429.2) million by 2040.

Conclusions

The amblyopia is becoming a significant vision problem worldwide. It is of great importance to design and implement amblyopia screening, treatment and related public health strategies.

Global and regional prevalence of strabismus: a comprehensive systematic review and meta-analysis

Purpose: Despite the importance of information on the prevalence of strabismus, which can be effective in planning preventive and curative services, no study has addressed its prevalence comprehensively. In this study, a systematic search was done to estimate the regional and global prevalence of strabismus in different age and sex groups and factors affecting prevalence heterogeneity. Methods: A comprehensive and systematic search was done in different international databases, including Web of Science, Scopus, PubMed, Embase, etc. to find published articles on the total prevalence of strabismus and the prevalence of exotropia and esotropia. A binomial distribution was used to calculate the prevalence and 95% confidence interval (CI). The Cochran's Q-test and I² were applied to evaluate heterogeneity and a random-effects model was used to assess the pooled prevalence. The Begg's test was administered to investigate publication bias and finally, a meta-regression method was applied to determine the factors affecting the heterogeneity among studies. Results: Of 7980 articles, 56 articles with a total sample size of 229,396 were analyzed. Many of these articles (n = 14) were from the Regional Office for the Americas. The estimated of pooled prevalence (95% CI) of any strabismus, exotropia, and esotropia was 1.93% (1.64-2.21), 1.23% (1.00-1.46), and 0.77% (0.59-0.95), respectively. The heterogeneity in prevalence of strabismus and its subtypes according to I² was above 95% (p value <.001 for all). Age had a direct effect on heterogeneity in the prevalence of exotropia (b: 3.491; p: 0.002). Moreover, WHO region had a significant direct effect on heterogeneity in the prevalence of strabismus (b: 0.482; p < .001) and esotropia (b: 0.168; p: 0.027), and publication year had a significant direct effect on heterogeneity in the prevalence of exotropia (b: 0.059; p: 0.045). Sample size and publication year did not have any association with strabismus nor with other variables. There was no publication bias according to the Begg's test. Conclusion: The prevalence of strabismus varies widely in the world. As for factors affecting heterogeneity in the prevalence of strabismus, the results showed that age affected heterogeneity in the prevalence of exotropia, WHO region affected heterogeneity in the prevalence of strabismus and esotropia, and publication year affected heterogeneity in the prevalence of exotropia. Information about the global prevalence of strabismus can help health care planners design interventions and prioritize resource allocation.

The prevalence of amblyopia in Iran: A systematic review

PURPOSE

The aim of this study was to determine the prevalence of amblyopia in the population of Iran.

METHODS

This article is a systematic review. A comprehensive search was conducted in PubMed, Scopus, Science Direct, Ovid, Web of Science, SID, Magiran, with appropriate terms. Information related to the sample size and the prevalence of amblyopia was extracted and summarized in tables. Analysis was performed using STATA software.

RESULTS

From 551 articles that were originally extracted from the databases, 31 articles met the criteria for entering the review. These studies were conducted in different regions of Iran. The prevalence of amblyopia in different regions varied between 0.19 and 3.69%. Study results were heterogeneous (I2 = 99.7%), and therefore, a meta-analysis was not done.

CONCLUSIONS

The prevalence of amblyopia in Iran is very different. In addition to conducting national screenings, it is necessary to report the incidence of amblyopia and its related factors in different parts of the country.

Global and regional estimates of prevalence of amblyopia: A systematic review and meta-analysis

Background: Amblyopia is one of the most important causes of vision impairment in the world, especially in children. Although its prevalence varies in different parts of the world, no study has evaluated its prevalence in different geographical regions comprehensively. The aim of the present study was to provide global and regional estimates of the prevalence of amblyopia in different age groups via a systematic search.Methods: In this study, international databases, including Embase, Scopus, PubMed, Web of Science, and other relevant databases, were searched systematically to find articles on the prevalence of amblyopia in different age groups published in English. The prevalence and 95% CI were calculated using binomial distribution. The Cochran's Q-test and I² statistic were applied to assess heterogeneity, a random-effects model was used to estimate the pooled prevalence, and a meta-regression method was utilized to investigate the factors affecting heterogeneity between studies.Results: Of 1252 studies, 73 studies were included in the analysis (sample volume: 530,252). Most of these studies (n = 25) were conducted in the WHO-Western Pacific Regional Office. The pooled prevalence estimate of amblyopia was 1.75% (95% CI: 1.62-1.88), with the highest estimate in European Regional Office (3.67%, 95% CI: 2.89-4.45) and the lowest in African Regional Office (0.51%, 95% CI: 0.24-0.78). The most common cause of amblyopia was anisometropia (61.64%). The I² heterogeneity was 98% (p < 0.001). According to the results of univariate meta-regression, the variables of WHO region (b: 0.566, p < 0.001), sample size (b: -0.284 × 10^-4, p: 0.025), and criteria for definition of amblyopia (b: -0.292, p: 0.010) had a significant effect on heterogeneity between studies, while age group, publication date, and cause of amblyopia had no significant effect on heterogeneity.Conclusion: The prevalence of amblyopia varies in different parts of the world, with the highest prevalence in European countries. Geographical location and criteria for definition of amblyopia are among factors contributing to the difference across the world. The results of this study can help stakeholders to design health programs, especially health interventions and amblyopia screening programs.

Are optometrists necessary in primary health care centres in Saudi Arabia?

Purpose: To determine the prevalence and visual characteristics of patients seen by optometrists and ophthalmologists in Saudi Arabian public hospitals. This model will demonstrate the efficacy, safety and effectiveness of optometrists as the primary point of contact for eye care in primary health care centres.Methods: A retrospective, analytical, record-based study of patients in 10 hospitals in Saudi Arabia was conducted over a period of 6 months. The hospitals were located in 3 of 14 provinces in Saudi Arabia. The current policy is that ophthalmologists be the first point of contact for patients in all hospitals. Ophthalmologists, optometrists and nurses collected the data using a predesigned data collection sheet (Appendix 1) which was divided into four sections – basic data, ocular information, ocular diagnosis and intervention. The pattern of patient examination in the eye clinics in public hospitals was analysed. Additionally, patients’ age, gender, nationality, symptoms, diagnosis and treatment were obtained from their medical records and considered for analysis. Diagnosis and treatment were classified by the scope of practice of optometrists and ophthalmologists: refraction, dispensing, rehabilitation of conditions of the visual system, detection, diagnosis and management of ocular diseases and referral to sub-specialty care were considered as optometric diagnoses. Prescription of medications and surgeries were classified as ophthalmologists’ diagnoses.Results: A total of 2601 patient records were reviewed from the pre-selected 10 public hospitals. There are approximately 415 public hospitals in Saudi Arabia. Refractive error was the most prevalent diagnosis; 54.5% of the patients were prescribed spectacles to relieve their symptoms of poor vision at distance and/or near. Around 35% of patients received treatment in the form of medications (20.6%), surgeries (11.4%), contact lenses (0.9%), orthoptics (1.8%) and low-vision devices (0.1%). About 0.6% patients were referred for major investigations such as ultrasonography, computed tomography and magnetic resonance imaging scans. No active intervention or treatment except observation was recommended for 7.7% of patients, and 2.4% of patients were referred to other sub-specialties. Based on the scope of practice and diagnostic criteria, the optometry discipline received the highest number of patients and can manage nearly 68% of patients registered for consultation; thus, they can take care of the predominant portion of eye-related problems in the outpatient services in the public hospital.Conclusion: This study clearly demonstrates that because of the disproportionate number of patients seeking care with refractive problems, optometrists can manage about two-thirds of patients visiting eye clinics of public hospitals. Thus, suggesting the need for optometrists as initial point of contact in terms of eye care services in primary health care centres. This would minimise the work load and appointment delays in public hospitals. This model will also enhance the early detection of vision-threatening eye conditions and assure appropriate referral to prevent future complications.

Visual Acuity Improvement in Continuous vs Divided Occlusion in Anisometropic Amblyopia

PURPOSE

To compare visual acuity improvement between continuous and split part-time occlusion for the treatment of moderate and severe anisometropic amblyopia.

METHODS

Randomised clinical trials in 6 - 13 y.o children with moderate and severe anisometropic amblyopia. Each patient was consecutively selected with continuous or split part-time occlusion. Best corrected visual acuity's improvement was followed up to six weeks and statistical data were analyzed using chi square and unpaired t-test.

RESULTS

Best corrected visual acuity's improvement was comparable between continuous and split part-time occlusion (0.20±0.27 vs 0.21±0.25; p = 0.79).

CONCLUSION

Split part-time occlusion may be considered as an alternative treatment for moderate and severe anisometropic amblyopia treatment.

The prevalence of visual disorders in Iranian students: A meta-analysis study and systematic review

Background

Visual defects have dramatic effects on health, self-esteem, and educational function of students, and delayed diagnosis will cause complications, like academic failure and psychologic disorders.

Objective

The present study aimed to investigate the prevalence of ocular disorders in Iranian students in a systematic review.

Methods

We searched databases, including PubMed, SID, Magiran, Google Scholar, and Iranmedex using the following keywords in Persian and English: disorders, vision, amblyopia, refractive errors, astigmatism, student, and Iran with all the possible combinations, important, chief, and sensitive words. Search resulted in 28 articles, conducted during a period from 1996 to 2014 in Iran and their data was analyzed using meta-analysis and random effects model. Heterogeneity of studies was assessed using I2 index, and data was finally analyzed with R Software and STATA (Version 11.2).

Results

Total number of subjects in the study was 1,117,274, aged 2 to 18 years. The prevalence of disorders related to amblyopia, refractive error, and strabismus was 8%, 7% and 1%, respectively. The greatest amount of refractive error was related to astigmatism (19%) followed by myopia (17%).

Conclusion

According to the study results, the prevalence of visual disorders among Iranian students indicated the critical necessity of screening programs for prevention of visual disorders in this age group.

Prevalence of ocular morbidity in school going children in West Uttar Pradesh

AIM OF THE STUDY

This study aims to evaluate the prevalence and to make a comparison between the ocular morbidity pattern in school going children of urban and rural areas of West Uttar Pradesh.

MATERIALS AND METHODS

A school-based cross-sectional study design was adopted to examine children aged 5-15 years in randomly selected urban and rural schools of West Uttar Pradesh from June 2012 to August 2014. An optometrist did the vision and refraction, and a detailed ophthalmic examination was done by an ophthalmologist. Children needing further assessment were referred to a higher center. Interpretation and analysis of the data were done using Epi Info Software and t-test.

RESULTS

A total of 4838 students (2271 males and 2567 females) were screened. The prevalence of ocular morbidity was 29.35% (28.65% urban, 30.05% rural). Refractive error (17.36%) was the major cause of ocular morbidity followed by convergence insufficiency (2.79%), blepharitis (2.11%), Vitamin A deficiency (2.09%), allergic conjunctivitis (1.92%), bacterial conjunctivitis (0.95%), amblyopia (0.41%), stye (0.31%) and squint (0.27%). There was an increase in ocular morbidity with age, especially in refractive error and convergence insufficiency. On comparing urban and rural schools, Vitamin A deficiency showed a significantly higher prevalence (P < 0.05%) in the rural (3.03%) as compared to the urban sector (1.15%). The prevalence of visual impairment was 4.9/1000 children, and prevalence of blindness was 0.62/1000 children.

CONCLUSION

This study was the first of its kind in West Uttar Pradesh, reporting a considerable high prevalence (29.35%) of pediatric ocular morbidity, which was more in rural as compared to the urban sector. Since most of this morbidity is either preventable or treatable, school screening forms an effective method to reduce this load.

Amblyopia Prevention Screening Program in Northwest Iran (Ardabil)

BACKGROUND

The aim of this study was to evaluate the results of amblyopia screening in Ardabil Province in three examination levels by kindergarten teacher, optometrist, and ophthalmologist.

METHODS

In a cross-sectional study, the results of the national amblyopic prevention program in 2-6 years old children in Ardabil Province were investigated in 2012. The results pertained to the examinations of children participating in this research were collected in the national approved forms. The data were entered into the computer and were analyzed using statistical methods in SPSS 18.

RESULTS

Around 38,844 children (51.7%) out of 75173 with 2-6 years old qualified children participated in the screening program in Ardabil Province. In the first stage of screening, 1068 children (33.1%) are visually impaired in one eye and 2160 children (66.9%) are visually impaired in two eyes. In the second stage, the results related to the examinations by optometrists indicated that the prevalence of refractive errors, strabismus, and others were 70%, 27.8%, and 2.2%, respectively. Refractive errors problem was most prevalent in Ardabil city (72.6%).The prevalence of refractive errors, strabismus, and other reasons in amblyopic children was 51.3%, 23.9%, and 24.8%; respectively.

CONCLUSIONS

The present investigation showed that coverage of amblyopia screening program was not enough in Ardabil Province. To increase the screening accuracy, standard instruments and examination room must be used; more optometrists must be involved in this program and increasing the validity of obtained results for future programming.

Interocular Difference of Peripheral Refraction in Anisomyopic Eyes of Schoolchildren

Purpose

Refraction in the peripheral visual field is believed to play an important role in the development of myopia. The purpose of this study was to investigate the differences in peripheral refraction among anisomyopia, isomyopia, and isoemmetropia for schoolchildren.

Methods

Thirty-eight anisomyopic children were recruited and divided into two groups: (1) both eyes were myopic (anisomyopic group, AM group) and (2) one eye was myopic and the contralateral eye was emmetropic (emmetropic anisomyopic group, EAM group). As controls, 45 isomyopic and isoemmetropic children were also recruited with age and central spherical equivalent (SE) matched to those of the AM and EAM groups. The controls were divided into three groups: (1) intermediate myopia group (SE matched to the more myopic eye of AM group), (2) low myopia group (SE matched to the less myopic eye of AM group and the more myopic eye of EAM group), and (3) emmetropia group (SE matched to the less myopic eye of EAM group). Peripheral refraction at 7 points across the central ±30° on the horizontal visual field with a 10° interval was measured with an autorefractor. Axial length (AL), corneal curvature (CC), and anterior chamber depth (ACD) were also determined by using the Zeiss IOL-Master.

Results

The relative peripheral spherical equivalent [RPR(M)] and relative peripheral spherical value [RPR(S)] of the more myopic eye was shifted more hyperopically than the contralateral eye in both the AM and the EAM groups (both p<0.0001). The RPR(M, S) of the less myopic eyes in the AM and EAM groups showed a relatively flat trend across the visual field and were not significantly different from the emmetropia group. The RPR(M, S) of less myopic eyes in the AM group were shifted less hyperopically than in the isomyopic low myopia group and the more myopic eye of the EAM group [RPR(M), p = 0.007; RPR(S), p = 0.001], although the central SEs of the three groups were not significantly different from each other. However, RPR(M, S) of the more myopic eyes were not different from the corresponding isomyopic groups. There was also no significant difference in the relative peripheral astigmatism [RPR(J0, J45)] between the more and the less myopic eyes in either the AM or the EAM group.

Conclusion

Refraction of anisomyopia differs between the two eyes not only at the central visual field but also at the off-axis periphery. The relative peripheral refraction of the more myopic eye of anisomyopia was shifted hyperopically, as occurs in isomyopia with similar central subjective SE values. Less myopic eyes were much less hyperopically shifted in relative peripheral refraction than the corresponding isomyopic eyes, but are comparable to emmetropic eyes. This emmetropia-like relative peripheral refraction in less myopic eyes might be a factor responsible for slowing down the progression of myopia.

Higher order aberrations in a normal adult population

PURPOSE

To determine the distribution of Zernike coefficients and higher order aberrations in a normal population and its relationship with age, gender, biometric components, and spherical equivalent.

METHODS

During the first phase of the Shahroud cohort study, 6311 people of the 40-64-year-old population of Shahroud city were selected through random cluster sampling. A subsample of participants was examined with Zywave aberrometer (The Bausch & Lomb, Rochester, NY) to measure aberrations. Measurements of aberrations were done before cycloplegic refraction, and values generated from a minimum pupil diameter of 5 mm were reported in this analysis.

RESULTS

After applying exclusion criteria, 904 eyes of 577 people were analyzed in this study and mean age in this study was 49.5 ± 5.7 years and 62.9% were female. Mean root-mean-square (RMS) of the third-, fourth-, and fifth-order aberrations was 0.194 μm (95%CI: 0.183 to 0.204), 0.115 μm (95%CI: 0.109 to 0.121), and 0.041 μm (95%CI: 0.039 to 0.043), respectively. Total RMS coma (Z3 (-1,) Z3 (1), Z5 (-1), Z5 (1)), Total RMS trefoil (Z3 (-3,) Z3 (3), Z5 (-3), Z5 (3)), and spherical aberration (Z4 (0)) in the studied population was 0.137 μm (95% CI:0.129-0.145), 0.132 μm (95% CI: 0.123-0.140), and -0.161 μm (95%CI:-0.174 to -0.147), respectively. Mean higher-order Zernike RMS in this study was 0.306 (95% CI: 0.295-0.318) micrometer, and in the multiple model, it significantly correlated with older age and short axial length. The highest amounts of higher-order RMS were observed in hyperopes, and the smallest in emmetropes. Increased nuclear opacity was associated with a significant increase in HO RMS (p < 0.001). Analysis of Zernike coefficients demonstrated that spherical aberration (Z4 (0)) significantly correlated with nuclear cataract only (age-adjusted Coef = 0.37 and p = 0.012).

CONCLUSION

This report is the first to describe the distribution of higher-order aberrations in an Iranian population. Higher-order aberrations in this study were on average higher that those reported in previous studies.

Prevalence of amblyopia in primary school children in Qassim province, Kingdom of Saudi Arabia

PURPOSE

To determine the prevalence and causes of amblyopia in primary school children in Qassim province, Kingdom of Saudi Arabia (KSA).

MATERIALS AND METHODS

In this cross sectional study, 5176 children, aged 6 to 13 years (mean - 9.53 ± 1.88 years) were evaluated. There were 2573 (49.71%) males and 2603 (50.29%) females. Distance visual acuity (V/A) was tested monocularly using a logMAR chart with and without correction. Cycloplegic refraction was performed in children with reduced vision. To determine the etiology of amblyopia, children were enrolled if there was a difference in V/A of two or more lines between eyes or an absolute reduction in acuity <20/30 in either eye, that could not be corrected by refraction. P ≤ 0.05 was considered statistically significant.

RESULTS

There 202 out of 5176 (3.90%) with ambylopia. There are 98 (1.88%) amblyopic females. There was no statistical difference in gender for amblyopes (P > 0.05). The prevalence of amblyopia was statistically significant higher in the older age group (10-13 year) compared to younger age group (6 to 9 years) (P < 0.05). Unilateral amblyopia (3.24%) was more frequent than bilateral amblyopia (0.66%). The most frequent causes of amblyopia were refractive error (94.56%), of which anisometropic amblyopia was present in 77.72%, isoametropic amblyopia in 16.84% and strabismus in 5.44%.

CONCLUSION

The prevalence of amblyopia in Qassim province, KSA, is 3.9% which is similar or higher than other published studies on amblyopia. Anisometropic refractive errors are the most common underlying cause for this population. We recommend implementation of visual screening programs for children with appropriate clinical and social settings for early detection and proper management of amblyopia.

Impact of laser refractive surgery on ocular alignment in myopic patients

PURPOSE

To evaluate the impact of myopic keratorefractive surgery on ocular alignment.

METHODS

This prospective study included 194 eyes of 97 myopic patients undergoing laser refractive surgery. All patients received a complete ophthalmic examination with particular attention to ocular alignment before and 3 months after surgery.

RESULTS

Patients with a mean age of 26.6 years and a mean refractive error of -4.83 diopters (D) myopia were treated. Asymptomatic ocular misalignment was present preoperatively in 46 (47%) patients: a small-angle heterophoria (1-8 prism diopters, PD) in 36%; and a large-angle heterophoria (>8 PD)/heterotropia in 11%. Postoperatively, the change in angles of 10 PD or greater occurred in 3% for distance and 6% for near fixation: in 7% of the patients with orthophoria, in 3% of those with a small-angle heterophoria, and in 18% of those with a large-angle heterophoria/heterotropia. No patient developed diplopia. The preoperative magnitude of myopia or postoperative refractive status was not related to the change in ocular alignment. The higher anisometropia was associated with a decrease in deviation (P=0.041 for distance and P=0.002 for near fixation), whereas the further near point of convergence tended to be related with an increase in near deviation (P=0.055).

CONCLUSIONS

Myopic refractive surgery may cause a change in ocular alignment, especially in cases with a large-angle heterophoria/heterotropia. There is also a chance of improvement of misalignment in patients with anisometropia.

The prevalence of anisometropia in population base study

PURPOSE

To determine the prevalence of anisometropia and its determinants in the population of Mashhad.

METHODS

In a cross-sectional study in 2008, 4453 residents of Mashhad city between the ages of 1 and 90 years were selected using stratified cluster sampling, of which 70.4% participated in the study. All respondents had visual acuity and refraction testing. Anisometropia was defined as the absolute interocular difference in the spherical equivalent based on non-cycloplegic refraction. The prevalence rates and 95% confidence intervals (CI) of anisometropia were determined based on cut points of 0.5 diopter (D), 1.0 D, and 2.0 D or more, and we used the 1.0 D cut point to examine associations.

RESULTS

After applying exclusion criteria, data from 2947 participants were used in the analyses. Based on cut points of 0.5 D, 1.0 D, and 2.0 D or more, the prevalence of anisometropia was 17.0% (n = 451) (95% CI, 15.1-18.8), 5.6% (n = 148) (95% CI, 4.6-6.6), and 1.7% (n = 50) (95% CI, 1.2-2.2), respectively. The odds of anisometropia showed a significant increase of 2.8% with every year of aging (P < 0.001); 2.6% and 2.8% were anisomyopic and anisohyperopic, respectively. The prevalence of anisometropia was directly associated with myopia (P < 0.001) as well as a history of ocular trauma (P < 0.001). The prevalence of anisoastigmatism was 5.6% and significantly increased with age (P < 0.001).

CONCLUSION

The prevalence of anisometropia in the studied population, compared to studies conducted in the Middle Eastern Region and East Asia, is in the midrange. The prevalence of anisometropia is higher at older age, however, children should receive more attention due to the risk of amblyopia. A history of ocular trauma is a risk factor for anisometropia.

All biometric components are important in anisometropia, not just axial length

BACKGROUND

No study to date has looked into the relationship between ocular biometrics with anisometropia exclusively; therefore, the purpose of this study was to determine the relationship between anisometropia and ocular biometrics.

METHODS

In a cross-sectional study with multistage cluster sampling, 6311 people in the 40-64-year-old age group from the population of Shahroud, Iran, were selected. Of these, 5190 people participated in the study. For all participants, tests for visual acuity, cycloplegic and non-cycloplegic refraction, slit lamp test and fundoscopy were performed. All participants underwent biometric examinations using the Allegro Biograph (WaveLight AG, Erlangen, Germany).

RESULTS

Asymmetry of axial length, corneal power, vitreous chamber depth, anterior chamber depth, lens thickness and lens power were significantly more among participants who were anisometropic than those who were non-anisometropic. The correlation of anisometropia with axial length asymmetry was 0.735, 0.273 with corneal power, 0.183 with anterior chamber depth and 0.311 with lens power (p<0.001). In a multiple linear regression model, anisometropia was found to have significant associations with axial length asymmetry (standard coefficient (SC)=0.905), corneal power asymmetry (SC=0.350), lens power asymmetry (SC=0.454), nuclear opacity asymmetry (SC=0.074) and age (SC=0.28) (R(2)=85.1%). According to the linear regression model, corneal power had the strongest association with anisoastigmatism.

CONCLUSIONS

Axial length asymmetry has the strongest correlation with anisometropia; nonetheless, other components of ocular biometrics such as corneal power, lens opacity, lens power and anterior chamber depth are related to anisometropia as well. More than 10% of changes in anisometropia can be explained with changes in factors other than asymmetry of ocular biometrics and lens opacity.

The prevalence of anisometropia and its associated factors in an adult population from Shahroud, Iran

BACKGROUND

The aim of this study was to evaluate the prevalence of anisometropia in an urban adult population in the north of Iran.

METHODS

This cross-sectional study was conducted among the 40-64-year-old population in Shahroud, Iran. Random cluster sampling was applied to select 6,311 people. Following an interview, optometric and ophthalmologic examinations, including objective non-cycloplegic refractions, were carried out. The prevalence of anisometropia was reported according to non-cycloplegic refraction and with cut-off points of 0.50, 1.00, 2.00 and 3.00 D.

RESULTS

Of the sampled people, 5,190 (82.2 per cent) took part in the study. After considering exclusion criteria, data from 4,918 participants were included in the final analysis. Most participants were female (57.6 per cent) and the average age (with standard deviation) was 50.7 ± 6.2 years. The prevalence of anisometropia with cut-off points of 0.50, 1.00 and 2.00 D were 23.1 (95%CI: 22.0-24.3), 7.7 (95%CI: 7.0-8.4) and 3.2 per cent (95%CI: 2.7-3.7), respectively. The prevalence of severe anisometropia (3.00 D or more) was 1.9 per cent (95%CI: 1.5-2.3). The odds ratio (OR) of anisometropia was 1.06 times higher for every year of increasing age. The OR of anisometropia in participants with cataract was 2.78 times more than in those without (p < 0.001). Anisometropia was more frequent among participants with unilateral cataract (21.7 per cent) compared to those with bilateral cataract (13.4 per cent). Anisometropia of 1.00 D or more was significantly more prevalent among myopic participants compared to hyperopic participants (13.8 versus 12.7 per cent, p < 0.001) and there was a stronger association between anisometropia and myopia (OR = 2.93) than hyperopia (OR = 2.23). With increasing educational level, the prevalence of anisometropia decreased significantly (p < 0.001). The prevalence of aniso-astigmatism of 1.00 D or more was 11.1 per cent (95%CI: 10.2-11.9).

CONCLUSION

In the present study, the prevalence of anisometropia in Iran was not negligible; however, it is less than in Eastern Asia. Myopia, cataract, age and educational level were associated with anisometropia.

Anisometropia in children from infancy to 15 years

PURPOSE

To investigate anisometropia in children from age 6 months to 15 years.

METHODS

Children with refractions at 6 months (n = 1120), 5 years (n = 395), and 12 to 15 years (n = 312) were included in this study. All children were refracted in the laboratory by noncycloplegic retinoscopy. Myopes had spherical equivalent refraction (SER) of the less ametropic eye of less than -0.50 D, hyperopes had SER of the less ametropic eye greater than or equal to 1.00 D, and emmetropes had SER of the less ametropic eye from -0.50 to +1.00 D.

RESULTS

The mean difference in refraction between the two eyes was similar at 6 months (0.11 D) and 5 years (0.15 D), increasing to 0.28 D at 12 to 15 years. Using a cutoff of 1.00 D SER for anisometropia, the prevalence was 1.96%, 1.27%, and 5.77% at 6 months, 5 years, and 12 to 15 years, respectively. At 12 to 15 years, the prevalence of anisometropia in the myopes was 9.64% and in the hyperopes was 13.64%, both significantly higher than that in the emmetropes (3.38%, P < 0.05). The degree of anisometropia at 12 to 15 years was significantly associated with the refractive error of the less ametropic eye at 12 to 15 years, with and without adjustment for relevant covariates (P < 0.05). Infants with significant astigmatism (cylinder power ≥ 1.00 D in one or both eyes) have an increased risk of anisometropia (P < 0.05).

CONCLUSIONS

The prevalence of anisometropia increases between 5 and 15 years, when some children's eyes grow longer and become myopic. However, anisometropia was found to accompany both myopia and hyperopia, suggesting that other mechanisms in addition to excessive eye growth may exist for anisometropia development, especially in hyperopia.

Prevalence of eye diseases and causes of visual impairment in school-aged children in Western China

Background

The present study investigated the prevalence of refractive error, visual impairment, and eye diseases in school-aged children in western China.

Methods

The survey was done in a representative county (Yongchuan District, Chongqing Municipality) of western China. Cluster random sampling was used to select children aged 6 to 15 years. We conducted door-to-door surveys and eye examinations including optometry, stereoscopic vision test, eye position and eye movement, slit lamp examination of the anterior segment, retinoscopy, and fundus examination after cycloplegia with 1% cyclopentolate.

Results

Among 3469 children, data were available for 3079 (88.76%). The prevalences of eye diseases were, in descending order, refractive error (20.69%; 637/3079), conjunctivitis (11.76%; 362/3079), amblyopia (1.88%; 58/3079), color vision defect (0.52%; 16/3079), keratitis (0.36%; 11/3079), strabismus (0.29%; 9/3079), cataract (0.23%; 7/3079), pathologic myopia (0.19%; 6/3079), and ocular trauma (0.13%; 4/3079). The prevalence of corneal leucoma, corneal staphyloma, optic neuropathy, macular degeneration, and myelinated nerve fibers was 0.03% (1/3079) for each. The prevalence of visual impairment was 7.70% (237/3079), and the major causes of visual impairment were uncorrected refractive error (86.08%; 204/237), amblyopia (9.70%; 23/237), pathologic myopia (1.27%; 3/237), congenital cataract (0.42%; 1/237), and others (2.11%; 5/237).

Conclusions

Among school-aged children in a less developed area of western China, refractive error was the most prevalent eye disorder, and uncorrected refractive error was the main cause of visual impairment.