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Erschienen in:
01.01.2014 | Pediatrics
Prevalence, causes and associations of amblyopia in year 1 students in Central China
The Anyang childhood eye study (ACES)
Erschienen in: Graefe's Archive for Clinical and Experimental Ophthalmology | Ausgabe 1/2014
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Background
Earlier diagnosis and treatment of amblyopia are associated with improved visual outcomes. This study reports the prevalence of amblyopia and associated factors in year 1 primary school students in central China.
Methods
The school-based, cross-sectional study involved 3,112 year 1 primary school students . All the participants underwent a comprehensive eye examinations including cycloplegic refraction, cover test and ocular movement examinations. The unaided and best corrected visual acuity (BCVA) was recorded. Unilateral amblyopia was defined as a 2-line interocular difference with BCVA ≤ 20/32 (≥ logMar 0.2) in the worse eye and with coexisting anisometropia (≥ 1.00 D SE for hyperopia, ≥ 3.00 D SE for myopia, or ≥ 1.50 D for astigmatism), strabismus or past or present visual axis obstruction. Bilateral amblyopia was defined as BCVA in both eyes<20/40 (> logMar 0.3), with coexisting hyperopia ≥ 4 D SE, myopia ≤ −6 D SE, or astigmatism ≥ 2.5 D, or past or present visual axis obstruction.
Results
Out of the 3,112 eligible students, 2,893 (93.0 %) students completed the examinations. The average age of the students was 7.1 ± 0.4 (mean ± standard deviation SD) years old. The prevalence of amblyopia was 1.0 % (95 % confidence interval [CI], 0.6 %–1.3 %) with no difference between the sexes (P = 0.88). Of the 27 amblyopic students, unilateral amblyopia was found in 18 (66.7 %) students, and bilateral amblyopia in 9 (33.3 %) students. Of 18 unilateral amblyopia, 13 were anisometropic amblyopia, 4 were strabismus amblyopia, 1 was mixed amblyopia. Of 9 bilateral amblyopia, 7 were isoametropic amblyopia, 2 were stimulus deprivation. The mean corrected VA of the amblyopic eyes was 30.50 logMAR letters (Snellen VA equivalent 4/12.6), and the range was 5 to 45 logMAR letters (Snellen VA equivalent 4/40-4/6.3). Most amblyopic eyes (38.9 %) were significantly hyperopic (spherical equivalent ≥ +3.00 D); 25.0 % were myopic. In addition, 58 (2.1 %) students had a previous amblyopia history of amblyopia that was not corroborated in this study.
Conclusions
The study shows a relatively low prevalence of amblyopia (1.0 %) in year 1 students in central China. Amblyopia is usually caused by abnormal refractive error.