Influence of interocular differences in the Strehl ratio on binocular summation.

The aim of this work is to determine the influence of interocular differences in retinal image quality on binocular visual performance. We measured the contrast sensitivity function (both monocular and binocular) and we computed binocular summation. Data on retinal image quality were taken from a double-pass device (OQAS, Optical Quality Analysis System; Visiometrics SL. Tarrasa, Spain), providing the Strehl ratio as a parameter to quantify retinal image quality. A total of 28 observers took part in the experiments. Binocular summation for the contrast sensitivity function was found to be significantly (p < 0.001) correlated with interocular differences in the Strehl ratio. The higher the interocular differences in the Strehl ratio, the lower the binocular summation. Binocular summation is less effective as the interocular differences in retinal image increase.