Prevalence of amblyopia and strabismus in a population of 7th-grade junior high school students in Central China: the Anyang Childhood Eye Study (ACES)

Refractive Errors and Concomitant Strabismus: A Systematic Review and Meta-analysis

This systematic review and meta-analysis is to evaluate the risk of development of concomitant strabismus due to refractive errors. Eligible studies published from 1946 to April 1, 2016 were identified from MEDLINE and EMBASE that evaluated any kinds of refractive errors (myopia, hyperopia, astigmatism and anisometropia) as an independent factor for concomitant exotropia and concomitant esotropia. Totally 5065 published records were retrieved for screening, 157 of them eligible for detailed evaluation. Finally 7 population-based studies involving 23,541 study subjects met our criteria for meta-analysis. The combined OR showed that myopia was a risk factor for exotropia (OR: 5.23, P = 0.0001). We found hyperopia had a dose-related effect for esotropia (OR for a spherical equivalent [SE] of 2–3 diopters [D]: 10.16, P = 0.01; OR for an SE of 3-4D: 17.83, P < 0.0001; OR for an SE of 4-5D: 41.01, P < 0.0001; OR for an SE of ≥5D: 162.68, P < 0.0001). Sensitivity analysis indicated our results were robust. Results of this study confirmed myopia as a risk for concomitant exotropia and identified a dose-related effect for hyperopia as a risk of concomitant esotropia.

Assessment of Cortical Dysfunction in Patients with Intermittent Exotropia: An fMRI Study

Neural imaging studies have found the connection between strabismus and brain cortex. However, the pathological mechanisms of intermittent exotropia are still not fully understood. In the present study, changes of binocular fusion related cortices in intermittent exotropia were investigated with blood oxygen level dependent functional magnetic resonance imaging. Activated cortices induced by fusion stimulus were found to be distributed in several regions such as bilateral middle occipital gyrus, bilateral middle temporal gyrus, left superior parietal lobule and so on. Compared with normal subjects, the increased activation intensity was observed in bilateral superior parietal lobule and inferior parietal lobule in subjects with intermittent exotropia. These findings indicate that binocular fusion involves a complicated brain network including several regions. And cortical activities of bilateral superior parietal lobule and inferior parietal lobule compensate for the binocular fusion dysfunction in intermittent exotropia.

Chinese Eye Exercises and Myopia Development in School Age Children: A Nested Case-control Study

Chinese eye exercises have been implemented in China as an intervention for controlling children’s myopia for over 50 years. This nested case-control study investigated Chinese eye exercises and their association with myopia development in junior middle school children. Outcome measures were the onset and progression of myopia over a two-year period. Cases were defined as 1. Myopia onset (cycloplegic spherical equivalent ≤ −0.5 diopter in non-myopic children). 2. Myopia progression (myopia shift of ≥1.0 diopter in those who were myopic at baseline). Two independent investigators assessed the quality of Chinese eye exercises performance at the end of the follow-up period. Of 260 children at baseline (mean age was 12.7 ± 0.5 years), 201 were eligible for this study. There was no association between eye exercises and the risk of myopia-onset (OR = 0.73, 95%CI: 0.24–2.21), nor myopia progression (OR = 0.79, 95%CI: 0.41–1.53). The group who performed high quality exercises had a slightly lower myopia progression of 0.15 D than the children who did not perform the exercise over a period of 2 years. However, the limited sample size, low dosage and performance quality of Chinese eye exercises in children did not result in statistical significance and require further studies.

Epidemiology of Intermittent Exotropia in Preschool Children in China

PURPOSE

To determine the prevalence, subtypes, and associated risk factors for intermittent exotropia (IXT) in preschool children aged 3 to 6 years in eastern China.

METHODS

A population-based study including 5831 preschool children aged 3 to 6 years was conducted from 2011 to 2012 in Yuhua District, Nanjing, China, using an age-stratified random sampling procedure. Clinical examinations including ocular alignment, ocular motility, visual acuity, prism cover test, cycloplegia refraction, stereopsis screening, slitlamp examination, and fundus examination were performed by trained ophthalmologists and optometrists. Intermittent exotropia was defined as an acquired intermittent exodeviation of at least 10 prism diopters in an otherwise healthy child following the classification recommended by the National Eye Institute.

RESULTS

The overall prevalence of IXT in this population was 3.24% (95% confidence interval, 2.79 to 3.69%), with no age (p = 0.19) and sex (p = 0.89) differences. Among 166 children with IXT, the "basic type" was the most common type of IXT (74.7%), the "divergence excess" was the second (19.9%), whereas the "convergence weakness" was the rarest (5.4%). In multivariate analysis adjusting for age, sex, and other confounders, the presence of IXT was only associated with a history of hypoxia at birth (odds ratio, 4.41; 95% confidence interval, 2.47 to 7.86).

CONCLUSIONS

Intermittent exotropia affected approximately 1 in 30 Chinese preschool-aged children in eastern China, indicating a relatively higher burden of this pediatric eye condition in the world's most populous country. The presence of IXT was strongly associated with a history of hypoxia at birth.

Burden of Ocular Motility Disorders at a Tertiary Care Institution: A Case to Enhance Secondary Level Eye Care

Aim:

To evaluate the profile of strabismus and amblyopia in patients presenting to a tertiary care institution in order to understand the disease burden.

Materials and Methods:

A retrospective, prospective hospital-based observational study was conducted at a tertiary level eye care hospital in India. All patients with strabismus or amblyopia who presented over a 1-year period were identified and referred to the squint clinic, where they were evaluated with a detailed clinical history and examination.

Results:

A total of 24475 patients were evaluated, of which 1950 had strabismus or amblyopia. The overall magnitude of amblyopia and strabismus was 2.0% [95% confidence interval (CI), 1.8-2.2)] and 6.9% (95% CI, 6.6-7.2), respectively. About 20% of those seeking an ophthalmic consultation were children and they constituted over half of the population referred to the squint clinic. Among younger children, the burden of amblyopia and strabismus was 84.4% and 26.6%, respectively. Among the referred patients, strabismus was noted in 84.6% (N = 1649), most of the cases of which was of the comitant subtype (78.1%, N = 1288) with an equal distribution of exotropia and esotropia. Paralytic [12.9% (N = 251)] and restrictive [4.7% (N = 85)] squint constituted the remaining burden of strabismus.

Conclusion:

Strabismus and amblyopia affect a sizeable proportion of patients presenting to a tertiary care ophthalmology setup. A significantly higher burden is present in the pediatric population. The majority of the cases of strabismus are of a comitant variety, which do not merit tertiary level eye care. There is a need to improve pediatric eye care at a secondary level to reduce the immense burden on tertiary referral centers.

Microstructural changes of the whole brain in patients with comitant strabismus: evidence from a diffusion tensor imaging study

OBJECTIVE

The aim of this study was to investigate the fractional anisotropy (FA) and mean diffusivity (MD) using a diffusion tensor imaging technique and whole-brain voxel-based analysis in patients with comitant strabismus.

PATIENTS AND METHODS

A total of 19 (nine males and ten females) patients with comitant strabismus and 19 age-, sex-, and education-matched healthy controls (HCs) underwent magnetic resonance imaging examination. Imaging data were analyzed using two-sample t-tests to identify group differences in FA and MD values. Patients with comitant strabismus were distinguishable from HCs by receiver operating characteristic curves.

RESULTS

Compared with HCs, patients with comitant strabismus exhibited significantly decreased FA values in the brain regions of the left superior temporal gyrus and increased values in the bilateral medial frontal gyrus, right globus pallidus/brainstem, and bilateral precuneus. Meanwhile, MD value was significantly reduced in the brain regions of the bilateral cerebellum posterior lobe and left middle frontal gyrus but increased in the brain regions of the right middle frontal gyrus and left anterior cingulate.

CONCLUSION

These results suggest significant brain abnormalities in comitant strabismus, which may underlie the pathologic mechanisms of fusion defects and ocular motility disorders in patients with comitant strabismus.

Altered intrinsic regional brain spontaneous activity in patients with comitant strabismus: a resting-state functional MRI study

OBJECTIVE

To investigate the underlying regional homogeneity (ReHo) of brain-activity abnormalities in patients with comitant strabismus (CS) and their relationship with behavioral performance.

METHODS

Twenty patients with CS (ten men and ten women) and 20 (ten men and ten women) age-, sex-, and education-matched healthy controls (HCs) underwent resting-state functional magnetic resonance imaging scans. The ReHo method was used to assess local features of spontaneous brain activities. Patients with CS were distinguished from HCs by receiver operating characteristic curve. Correlation analysis was performed to explore the relationship between the observed mean ReHo values of the different brain areas and behavioral performance.

RESULTS

Compared to HCs, the patients with CS showed significantly increased ReHo values in the right inferior temporal cortex/fusiform gyrus/cerebellum anterior lobe, right lingual gyrus, and bilateral cingulate gyrus. We did not find any relationship between the observed mean ReHo values of the different brain areas and behavioral performance.

CONCLUSION

CS causes dysfunction in many brain regions, which may explain the fusion compensation in CS.

Ultrastructure of medial rectus muscles in patients with intermittent exotropia

PURPOSE To study the ultrastructure of the medial rectus in patients with intermittent exotropia at different ages.PATIENTS AND METHODS The medial recti were harvested surgically from 20 patients with intermittent exotropia. Patients were divided into adolescent (age<18 years, n=10) and adult groups (age >18 years, n=10). The normal control group included five patients without strabismus and undergoing eye enucleation. Hematoxylin and eosin staining and transmission electron microscopy were used to visualize the medial recti. Western blot was used to determine the levels of myosin and actin.RESULTS Varying fiber thickness, atrophy, and misalignment of the medial recti were visualized under optical microscope in patients with exotropia. Electron microscopy revealed sarcomere destruction, myofilament disintegration, unclear dark and light bands, collagen proliferation, and fibrosis. The adolescent group manifested significantly higher levels of myosin and actin than the adult group (P<0.05).CONCLUSION Younger patients with intermittent exotropia show stronger contraction of the medial recti compared with older patients. Our findings suggest that childhood was the appropriate time for surgery as the benefit of the intervention was better than in adulthood.

Prevalence of amblyopia and strabismus in Eastern China: results from screening of preschool children aged 36-72 months

PURPOSE

To determine the prevalence of amblyopia and strabismus in preschool children in Eastern China.

METHODS

The Nanjing Pediatric Vision Project was a cross-sectional, population-based cohort study conducted in preschool children aged 36-72 months from 2011 to 2012 in Yuhua District, Nanjing, China, using an age-stratified random sampling procedure. A questionnaire totalling 117 items was sent to be completed by the corresponding parents or legal guardians of each eligible child. Comprehensive eye examinations, including visual acuity, anterior segment examination, autorefraction, cover test and ocular motility, were conducted. Postcycloplegic refraction and fundus examinations were performed if necessary.

RESULTS

Amblyopia was present in 68 children (1.20%, 95% CI 0.92% to 1.48%), with no statistical differences in gender (p=0.903) and age (p=0.835). Among these, 27 had bilateral amblyopia and 41 had unilateral amblyopia, including 26 anisometropic without strabismus, 26 binocular refractive, 7 strabismic, 6 combined strabismic/anisometropic and 3 deprivation amblyopia. Strabismus was found in 320 children (5.65%, 95% CI 5.05% to 6.25%), including 43 with concomitant esotropia, 259 with concomitant exotropia (1 esotropia at near but exotropia at distance), 8 with microtropia (3 esotropia and 5 exotropia), 10 with pure vertical strabismus (3 dissociated vertical deviation and 7 oblique muscle dysfunction) and 1 with Type I Duane syndrome. The prevalence of strabismus had no statistical differences in gender (p=0.952), but had significant statistical differences between different age groups (p=0.021).

CONCLUSIONS

The prevalence of amblyopia and strabismus in preschool children in Eastern China were 1.20% and 5.65%, respectively. The refractive and strabismus are the main factors associated with amblyopia.

Association between childhood strabismus and refractive error in Chinese preschool children

PURPOSE

To investigate the association between concomitant esotropia or concomitant exotropia and refractive error in preschool children.

METHODS

A population-based sample of 5831 children aged 3 to 6 years was selected from all kindergartens in a representative county (Yuhuatai District, Nanjing, Jiangsu Province) of Nanjing, China. Clinical examinations including ocular alignment, ocular motility, visual acuity, optometry, stereopsis screening, slit lamp examination and fundus examination were performed by trained ophthalmologists and optometrists. Odd ratios (OR) and 95% confidence intervals (95% CI) were calculated to evaluate the association of refractive error with concomitant esotropia and concomitant exotropia.

RESULTS

In multivariate logistic regression analysis, concomitant esotropia was associated independently with spherical equivalent anisometropia (OR, 3.15 for 0.50 to <1.00 diopter (D) of anisometropia, and 7.41 for > = 1.00 D of anisometropia) and hyperopia. There was a severity-dependent association of hyperopia with the development of concomitant esotropia, with ORs increasing from 9.3 for 2.00 to <3.00 D of hyperopia, to 180.82 for > = 5.00 D of hyperopia. Concomitant exotropia was associated with astigmatism (OR, 3.56 for 0.50 to 1.00 D of astigmatism, and 1.9 for <0.00 D of astigmatism), myopia (OR, 40.54 for -1.00 to <0.00 D of myopia, and 18.93 for <-1.00 D of myopia), and hyperopia (OR, 67.78 for 1.00 to <2.00 D of hyperopia, 23.13 for 2.00 to <3.00 D of hyperopia, 25.57 for 3.00 to <4.00 D of hyperopia, and 8.36 for 4.00 to <5.00 D of hyperopia).

CONCLUSIONS

This study highlights the close associations between refractive error and the prevalence of concomitant esotropia and concomitant exotropia, which should be considered when managing childhood refractive error.