Contrast sensitivity as a function of exposure duration in the amblyopic visual system.

The spatiotemporal differences between the normal and amblyopic visual systems were investigated by measuring contrast sensitivity as a function of exposure duration for specific spatial frequencies of a sine-wave grating. At threshold, normal subjects had contrast-time reciprocity curves with slopes of approximately 0.7, indicating less than perfect temporal summation. The integration time (critical duration) varied as a function of spatial frequency with longer integration times for higher spatial frequencies (in agreement with previous studies). Amblyopic subjects had integration times and reciprocity slopes that were similar to the normals for low spatial frequencies; however, at high spatial frequencies there were significant differences. These results show that an amblyopic eye may either lack sustained neurons or alternately have sustained neurons with abnormal response characteristics.