Objective Measurement of Local Rod and Cone Function Using Gaze-Controlled Chromatic Pupil Campimetry in Healthy Subjects

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 30° central visual field were analyzed in 14 healthy subjects (4 males, 34 ± 11 years, mean ± 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% ± 6.3%) with a hill-shaped decrease from the fovea to the periphery. For the rod-favoring protocol (RodProt), it was smaller (center, 13.5% ± 4.5%) with a profile lacking the central peak. Mean latency to constriction onset was faster for cones (277 ± 25 ms) than for rods (372 ± 13 ms). Mean intraclass correlation at the different stimulus locations was 0.84 ± 0.08 for RodProt and 0.75 ± 0.11 for ConeProt; mean coefficients of repeatability value of all stimulus locations was 5.9% ± 1.2% and 8.6% ± 1.7%, respectively.

Conclusions: CPC provides an objective evaluation of local rod and cone function within the central 30° 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.