Transient Pupillary Light Reflex in Relation to Fundus Autofluorescence and Dark-Adapted Perimetry in Typical Retinitis Pigmentosa

Abstract

Purpose: To determine whether the pupillary light reflex (PLR) can serve as an indicator of photoreceptor function in patients with advanced typical retinitis pigmentosa (RP). Methods: Dark-adapted transient PLRs elicited by blue or white light over a luminance range of 4 log units were recorded from 27 eyes of 19 patients with advanced RP. Retinas were characterized according to fundus autofluorescence (AF) and dark-adapted perimetry. We qualitatively analyzed whether PLR thresholds were correlated with AF patterns or scotopic sensitivity. Quantitative analysis included correlations between relative pupillary constrictions (RPCs) elicited by blue light (≤–1 log cd/m²) and the area of abnormal ring or central AF, and between RPCs elicited by white light and perimetric mean sensitivity. Results: The PLRs of all patients showed varying degrees of threshold elevation and relative afferent pupil defects. We classified three types of abnormal fundus AF: abnormal ring AF, abnormal central AF, and fragmentary AF. PLR thresholds were largely consistent with the patterns of AF and scotopic sensitivity. Rod-mediated RPCs were not correlated with the area of the abnormal ring AF (p > 0.05), but were correlated with the area of abnormal central AF (p < 0.05). RPCs elicited with a white stimulus (–0.3 or 0.7 log cd/m²) were significantly correlated with the mean sensitivity of the dark-adapted perimetry. Conclusions: PLR testing is a powerful technique for assessing photoreceptor dysfunction. The high correlation with AF and dark-adapted perimetry suggests that the key to quantifying photoreceptor function using the transient PLR is to optimize the luminance of the stimulus.