Binocular interaction in lesions of the visual pathways:III. Retrochiasmal lesions

Abstract

Binocular interaction was studied in central vision in subjects with retrochiasmal lesions of the visual pathways. Summation was measured using two contrast detection tests and two resolution tests. Stereo vision was measured with conventional clinical tests and a novel quantitative test. Subjects with homonymous hemianopia due to optic tract or occipital lobe lesions showed subnormal summation in the contrast sensitivity tests, while summation in the resolution tests was normal. Subjects with callosal division showed normal summation in the contrast sensitivity tests, while summation in the resolution tests was absent. At least one subject in each group performed normally in conventional stereo tests. It is concluded that summation of contrast sensitivity is possible within one single hemisphere although with reduced efficiency. Summation of resolution tasks seems to require intact callosal connections.

Key Words:

• binocular summation
• corpus callosum
• hemianopia
• optic tract
• visual cortex