The Effect of Monocular Vision Decline on Binocular Contrast Sensitivity

Objective: To study the changes in binocular contrast sensitivity (CS) when monocular vision declines, and to explore the effects of monocular vision decline on binocular function and interaction, and to explore the value of judicial appraisal. Methods: In this experimental study, 46 normal subjects (24 males and 22 females) were enrolled in Academy of Forensic Science from March 2016 to August 2017. Monocular visual acuity of them could be corrected to more than 4.9. Experimental lenses were placed in front of the dominant eyes to induce experimental monocular visual impairment in varying degrees. Visual acuity and CS for monocular and binocular function were measured. Binocular summation ratios (BSR) were calculated, further spherical tests, analysis of variance and the Kruskal-Wallis test. Results: Decreased monocular vision can cause a certain decrease in binocular vision, but binocular vision is still better than monocular vision. When visual acuity declined to the level of mild damage, the normal inverted U-shaped curve of the whole frequency band was destroyed, and visual acuity had a more obvious decline at medium and high spatial frequencies than at low spatial frequencies. At high frequencies and normal visual acuity in both eyes, the maximum sum of both eyes appeared (BSR=1.48). When monocular visual acuity gradually declined, the binocular average and inhibition appeared (BSR<1). There was a certain degree of tolerance and spatial dependence with binocular interaction. Conclusions: Decreased monocular vision has a certain influence on binocular CS and the form and degree of binocular interaction. A binocular CS test can reflect the degree of monocular vision loss. It has practical value and is worthy of clinical application and judicial expertise. Key words: monocular visual acuity; binocular contrast sensitivity; binocular interaction