The effect of experimental strabismus on the development of vernier acuity and grating acuity was studied in Macaca nemestrina monkeys. Six monkeys were studied longitudinally beginning near 10 days after birth. Four of the six monkeys developed amblyopia. As is true for human strabismic amblyopes, the deficit in vernier acuity was larger than the deficit in grating acuity in the amblyopic monkeys. The developmental data reveal that this differential disruption of vernier acuity can be understood as a result of a slowed developmental process associated with amblyopia.

The developmental time courses for vernier acuity and grating acuity were measured longitudinally in infant Macaca nemestrina monkeys. Behavioral measurements of vernier and grating acuity were made at regular intervals during development. Near birth, grating acuity is relatively more mature than vernier acuity. The proportional rate of vernier acuity development is faster than that for grating acuity. During the course of development, grating acuity improves approximately 15-fold whereas vernier acuity improves about 60-fold. Both visual functions approach adult levels at about the same age, around 40 weeks postnatally. Although grating acuity develops about four times faster in monkeys than in humans, vernier acuity development in monkeys and humans does not appear to reflect the same relationship. Adult levels of vernier acuity for the monkeys are about a factor of 2 poorer than are typically reported for humans. The differential development of vernier acuity and grating acuity does not necessarily reflect development at different levels of the visual system.