Binocular interaction in lesions of the visual pathways:II. Lesions of the optic chiasm

Abstract

Binocular summation was measured with a battery of tests of central vision in subjects with midchiasmal visual pathway lesions. All had stable lesions and well preserved visual acuity. In two contrast sensitivity tests, in which substantial binocular summation normally is found, most subjects showed neither summation nor inhibition. Instead binocular sensitivity approximated best monocular sensitivity. In a resolution test a small summation was found, similar to that of normal subjects. Midchiasmal lesions affect primarily the crossing chiasmal fibers. This effectively causes a neuronal separation of the visual pathways to the two hemispheres. This separation abolishes summation of contrast sensitivity but not of resolution.

Key Words:

• binocular summation
• differential light sensitivity
• optic chiasm
• resolution
• visual cortex