The effect of pupil size on binocular summation at suprathreshold conditions

Abstract

Purpose. To determine the influence of retinal illuminance on monocular or binocular visual reaction time (VRT).Methods. On two normal subjects, uniform circular stimuli were presented with respect to a reference stimulus at the fovea under suprathreshold conditions, and the detection of positive and negative luminance variations was recorded. Binocular and monocular reaction times were measured (by the index finger pressing on a mouse key) for viewing with both natural and artificial pupils.Results. Binocular reaction times were shorter than monocular reaction times; nevertheless, this binocular-summation effect was less marked in trials with the artificial pupil. Analyses of binocular-summation ratios for contrast changes for both pupil types indicated maximum and minimum binocular-saturation values depending on contrast variations in both positive and negative luminance changes.Conclusions. Binocular summation can be influenced by pupil size under suprathreshold conditions. Results are discussed in terms of retinal illuminance and cortical pupil response mechanisms.

Binocular Visual Performance After LASIK

“…The results of Campbell and Green 26 for threshold-contrast experiments showed binocular-summation data were slightly lower in the case of the artifi cial pupil (1.44) with respect to a natural one (1.43). For other visual functions, such as visual reaction time, 35 this decline also was detected in the case of the artifi cial pupil. In any event, threshold-contrast experiments 26 show that quantitatively, the infl uence is minor and does not account for all of the binocular summation.…”

“…In our case, we found no correlation (PϾ.05) between the binocular-summation data and pupil size before and after surgery, which is in agreement with the results reported by other authors. 33 In any case, it should be taken into account that on determining the contrast sensitivity function and the disturbance index binocularly, the pupil-size data are lower in the binocular case, 10,35 thereby minimizing the effects of the aberrations in the binocular case. The results of Campbell and Green 26 for threshold-contrast experiments showed binocular-summation data were slightly lower in the case of the artifi cial pupil (1.44) with respect to a natural one (1.43).…”