Meridional variations in acuity and CSF's in monkeys (Macaca nemestrina) reared with externally applied astigmatism.

Infant macaque monkeys have been raised under such conditions that all visual experience was obtained while looking through a cylindrical lens. When tested at older ages, these monkeys were found to have meridional differences in acuity and contrast sensitivity. The direction of the differences were predictable on the basis of the defocus produced by the rearing condition. The data support the theory, previously suggested on the basis of clinical and correlational studies, that astigmatism is a major cause factor in the occurrence of meridional amblyopia.