The effects of physostigmine sulphate eyedrops on human visual function

Instillation of 0.25% physostigmine sulphate eyedrops in twelve subjects caused a sustained miosis, a transient reduction in near-point and a transient increase in the amplitude of accommodation. The latter had a peak at 30 min and had recovered by 90 min, though its amplitude varied widely between subjects. Contrast sensitivity to stationary grating patterns of 3-30 cycles/deg and phase-reversed grating patterns of 0.5-3 cycles/deg was reduced transiently with a time course similar to that of the increase in accommodation. The peak reduction in contrast sensitivity was correlated significantly with the peak amplitude of accommodation. Contrast sensitivity to laser interference fringes, observed in Maxwellian view where the effects of defocus are bypassed, was also reduced, indicating that physostigmine also had a direct deleterious action on the visual system.