Objective measurement of local rod and cone function using gaze-controlled chromatic pupil campimetry in healthy subjects

Abstract

Purpose: We introduce a new approach for functional mapping of rod and cone activity by measuring pupillary responses to local stimulation via gaze-controlled chromatic pupil campimetry (CPC). Methods: Pupillary constriction amplitude and latency to constriction onset to local photopic and scotopic light stimuli at different locations within the 308 central visual field were analyzed in 14 healthy subjects (4 males, 34 6 11 years, mean 6 standard deviation [SD]). All subjects were measured twice for evaluating the test–retest variability and reproducibility of the method. Results: For the cone-favoring protocol (ConeProt), the relative maximal constriction amplitude was most pronounced in the center (26.8% 6 6.3%) with a hill-shaped decrease from the fovea to the periphery. For the rod-favoring protocol (RodProt), it was smaller (center, 13.5% 6 4.5%) with a profile lacking the central peak. Mean latency to constriction onset was faster for cones (277 6 25 ms) than for rods (372 6 13 ms). Mean intraclass correlation at the different stimulus locations was 0.84 6 0.08 for RodProt and 0.75 6 0.11 for ConeProt; mean coefficients of repeatability value of all stimulus locations was 5.9% 6 1.2% and 8.6% 6 1.7%, respectively. Conclusions: CPC provides an objective evaluation of local rod and cone function within the central 308 visual field. It shows a photoreceptor-specific profile in healthy subjects. Due to its easy, noncontact, gaze-controlled character, it is a clinically applicable method and may fill the gap of functional diagnostics of rods and cones of the human retina. Translational Relevance: Chromatic pupil campimetry provides information about the local rod and cone function of the human retina with distinct pattern of distributions in an objective manner.