Temporal sensitivity in amblyopia: an explanation of conflicting reports

Although the spatial characteristics of contrast sensitivity in amblyopia are well established, it is still not clear how temporal vision is affected. A wide range of spatial stimuli have been used to measure flicker sensitivity in amblyopia and we have considered the possibility that reported inconsistancies in results are due to a confounding of spatial and temporal stimulus parameters. To address this question we have measured contrast sensitivity from a sample of eight strabismic/anisometropic amblyopes using (1) stationary sinusoidal gratings, (2) uniform field flicker and (3) counterphased flickering gratings. In each case the contrast sensitivity deficits were predictably determined by the spatial properties of the stimulus (spot size or spatial frequency), and the spatial characteristics of the amblyopia. Results are nearly independent of the temporal properties of the stimulus. Specifically, when the stimulus is sufficiently large, or consists of low spatial frequencies, no temporal deficits are found. We conclude that conflicts between previous reports are attributable primarily to differences in spatial characteristics of the stimuli used.