Study of visual acuity in myopic children under low contrast levels

Objective To study variations in visual acuity at multiple contrast levels and discuss the inherent differences as well as related factors by measuring the subjective vision of myopic children.Methods This was a cross-sectional study.The corrected visual acuity of 76myopic children aged nine to fifteen years was measured at different contrast levels (100％,25％,10％,5％) with a multifunctional visual acuity tester.Myopia ranged from -1.12 to -6 D.LogMAR contrast visual acuity was recorded.The correlation of visual acuity with age,spherical equivalent refraction and astigmatism was analyzed.Results ①At contrast levels of 100％,25％,10％,5％,the average visual acuities of the myopic children were -1.007,0.067,0.303 and 0.558,respectively.LogMAR values gradually increased with a decline in contrast levels (F＝321,P＜0.01).Contrast visual acuity decreased linearly at low contrast intervals.②The children were divided into two groups based on their contrast visual scuties.Children with lower contrast visual acuity accounted for 30.3％.There were no statistical differences between the two groups when age,spherical equivalent refraction and astigmatism were compared.③here were no statistical differences in contrast visual acuity between the two groups when age,spherical equivalent refraction and astigmatism were compared.Conclusion Contrast visual acuity in myopic children decreased linearly at low contrast intervals and was not affected by age,low and moderate myopia or astigmatism.Individual differences may infer the susceptibility of myopic progression. Key words: Myopia; Chillren; Contrast visual acuity