Effects of Binocular Acuity in Visual Impairment Assessment

Author(s): Guangfeng Wu, Lan Wang, Baozeng Li, Chao Zai, Shanyao Zhao, Hong Cao

Objective: To study the correlations and differences between best corrected visual acuity in the better eye (hereinafter referred to as monocular acuity in the better eye) and binocular acuity after both eyes were best corrected separately (hereinafter referred to as binocular acuity), the relationship between both monocular acuity in the better eye and binocular acuity and reading acuity as well as reading speed were discussed in order to investigate the effect of binocular acuity in visual impairment and visual disability assessment. Methods: Two thousand a hundred and fifteen subjects ranging in age from 18 to 40 years old were recruited for the study, whose best corrected monocular acuity were less than or equal to 0.8, and other visual functions examined were normal. Best corrected visual acuity was measured monocularly and binocularly using Standard Logarithm Distance Charts. Reading visual acuity and reading speed were also determined. Experimental data were statistically analyzed using SPSS19.0 statistical software. Results: Monocular acuity in the better eye and binocular acuity was linear correlation (r=0.920, P<0.001), and the differences of them were statistically significant (Z=-23.025, P<0.05); Reading acuity and both monocular acuity in the better eye and binocular acuity were also linear correlation (r=0.827, P<0.001; r=0.862, P <0.001); Reading acuity deteriorated with aggravation of visual impairment.There were no differences of reading speed in visual impairment individuals that more than or equal to 0.3; However ,reading speed in visual disability (visual acuity was less than 0.3) individuals were slowed down significantly. Conclusions: Both of monocular acuity in the better eye and binocular acuity could estimate visual function preferably. There were also differences between both of them. In view of people are simultaneously using both eyes in daily life, it is suggested that the visual function of binocular acuity was recommended in the evaluation of judicial forensic visual impairment and visual disability.

Binocular acuity, Visual disability, Visual impairment, Visual function

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