Abstract
Binocular summation was studied in subjects with steady-state, unilateral optic neuropathy, using a battery of tests of central vision. The tests included differential light sensitivity, minimum visible, resolution, hyperacuity and pattern recognition. The subjects did not show normal summation in differential light sensitivity and hyperacuity tests. Instead, binocular inhibition or averaging was found in four of the five subjects. There was no significant difference compared to normal subjects in the other tests. Binocular inhibition or averaging of contrast sensitivity may be the cause of many complaints in minor unilateral optic neuropathy.