The effect of pilocarpine on the visual field in normals

Despite generalized consensus that pilocarpine-induced miosis results in some degree of visual field constriction, studies describing the predictability of this occurrence, as well as the nature of the field defects that may be seen, have not been undertaken. We studied 20 normal subjects, ranging in age from 24 to 57 years. Baseline refraction, pupillary measurements, and visual fields were performed in both eyes on a standardized Goldmann perimeter with the I-2e, I-3e, and I-4e test objects. Pilocarpine 2% was then instilled into the study eye and the field repeated at 30 and 120 minutes. An IBM PC computer program, designed by the authors, was used to calculate the area contained within each isopter. The probability of visual field constriction at 30 and 120 minutes after instillation of pilocarpine was found to be significant, especially with pupillary diameters of 2 mm or less. The I-2e isopter was most sensitive to miosis. Visual field constriction persisted with correction of ciliary spasm induced myopia, suggesting that miosis, especially when marked, can independently alter the visual field. The clinician, then, should make every effort to control visual field testing conditions in glaucoma patients on miotics to allow reliable serial comparisons.