Central and peripheral residual vision in humans with bilateral deprivation amblyopia.

Abstract

Residual visual capacities were investigated in the central and peripheral visual fields of 13 patients with bilateral deprivation amblyopia secondary to congenital cataracts removed at an early age. In comparison with a control group of normal subjects, spatial modulation sensitivity function of the amblyopes was markedly impaired in each experimental condition, i.e. both when the stimuli were stationary or drifting (8 Hz) gratings and both in central or peripheral visual field, at 10 and 20 degrees eccentricity. The sensitivity drop was observed over the whole spatial frequency range, although it was much more severe at high frequencies. Threshold elevation, with respect to controls, was very similar in conditions using stationary or drifting gratings, suggesting that both sustained and transient mechanisms are affected by stimulus deprivation amblyopia. Temporal modulation sensitivity function was uniformly impaired over the whole temporal frequency range. When compared with other types of amblyopia, this pattern of spatiotemporal sensitivity loss appeared characteristic of deprivation amblyopia. The peripheral deficit was particularly striking by its severity and extent, as ascertained by static perimetry and visual acuity measurements up to 50 degrees eccentricity. This finding emphasizes the susceptibility of peripheral as well as central human vision to early deprivation and suggests that peripheral visual functions are still immature in newborns. Finally, the overall deficit varied with the severity of the deprivation, in that patients with complete neonatal cataract performed much worse than those with incomplete cataract.