Automated Pupil Perimetry in Amblyopia: Generalized Depression in the Involved Eye

Abstract

This study was designed to determine whether the relative afferent pupillary defects observed commonly in amblyopic eyes are associated with a uniform depression of the pupillary light reflex throughout the visual field or solely by a focal decrease in pupillary response near fixation. The authors used pupil perimetry to evaluate the contraction amplitude of the pupil in response to focal light stimuli at 76 points throughout the 30 degrees field in each eye of 28 patients with amblyopia. The "pupil fields" were recorded using a computerized infrared pupillograph linked to a Humphrey Field Analyzer, so that the pupil contraction could be recorded in response to perimetric light stimuli. Nine patients had strabismic amblyopia, ten had anisometropia, six had a combination of anisometropia and strabismus, and three had deprivation amblyopia due to monocular congenital cataract. Mean pupillary contraction amplitude for the entire field and focal amplitudes at each tested location were compared. Mixed-model analysis of variance was used to assess effects of perimetry location, type of amblyopia, and interaction effects. The overall average of all the pupil contractions throughout the 30 degrees field was less for the amblyopic eye compared with that of the fellow eye. This decrease in focal pupil response for amblyopic eyes was present in each type of amblyopia and was greatest for deprivation amblyopia. The contraction amplitude was depressed diffusely throughout the pupil field and showed neither focal deficits nor a selective depression about fixation. Amblyopia produces a global depression of focal pupillary responses across the entire 30 degrees field.