Pathophysiology of binocular vision and amblyopia

Abstract

This article focuses on three important issues that have received much attention during the past year. The first is sensitive periods for amblyopia. Recent physiological studies suggest a surprising degree of neural plasticity in the adult visual cortex. A review of the literature suggests that at least some human amblyopes retain cortical plasticity into adulthood. The second issue is new methods of treatment for amblyopia. Certain neurotransmitters have been implicated in neuronal plasticity. Based on this finding, a potentially promising new method for treating amblyopia, levodopa, is being tested in adults and children with amblyopia. Unfortunately the early results provide more questions than answers. The third topic is neural mechanisms of amblyopia. In primates and humans, the weight of evidence suggests that the neural effects of strabismus and anisometropia are expressed primarily in the cortex. These cortical effects are expressed in a loss of cortical neurons and in alterations in the contrast sensitivity and range of preferred spatial frequencies of the neurons dominated by the amblyopic eye. The relationship between these physiological effects and psychophysical performance is reviewed.