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. 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 a parts per thousand currency signaEuro parts per thousand 20/32 (a parts per thousand yen logMar 0.2) in the worse eye and with coexisting anisometropia (a parts per thousand yen 1.00 D SE for hyperopia, a parts per thousand yen 3.00 D SE for myopia, or a parts per thousand yenaEuro parts per thousand 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 a parts per thousand yenaEuro parts per thousand 4 D SE, myopia a parts per thousand currency signaEuro parts per thousand a'6 D SE, or astigmatism a parts per thousand yenaEuro parts per thousand 2.5 D, or past or present visual axis obstruction. 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 a parts per thousand yenaEuro parts per thousand+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. 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.
