Pupil campimetry: An objective measurement of local rod and/or cone function by pupillary response

Abstract

Purpose : In clinical routine and therapy trials an objective measure of local photoreceptor function is still a challenge. We present a new method of gaze-controlled pupil campimetry designed to measure specific local function of rods and cones.

Methods : The gaze-controlled pupil campimetry with rod-specific and cone-specific protocols was performed in 10 (age=35±9; M=3; F=7) healthy subjects. The stimuli are presented on an OLED monitor with the following parameters: A) cones: red 3 degree stimuli of 620 nm ± 30 nm, 60 cd/m2, 1 sec, 1.7x10^-5 Watt and B) rods: blue 5 degrees stimuli of 460 nm ± 30 nm, 0,01 cd/m², 100ms, 2.1x10^-8 Watt after 20 minutes of dark adaptation. The stimuli were present in the central 30 degrees of the visual field at 41 positions for cones and 33 positions for rods. The measurements in all subjects were performed twice to evaluate the reliability of the method.

Results : In the cone-specific protocol, the pupil responses show a high level of eccentricity modulation with a peak at the fovea. The peripheral pupil responses were reduced around four times in comparison to the central responses. In the rod-specific protocol, the slope of eccentricity was much smaller (Fig. 1). Interclass correlation (ICC) was used as the test of reproducibility between the two measurements. In both, cone and rod-specific protocols, the ICC showed a good reproducibility between the repeated measurements. The maximal ICC was at the fovea in the cone protocol (ICC=0.81) and minimum at 30° (ICC=0.72). For rods, the maximal ICC = 0.8 was at the eccentricity of 12° and the minimum at 30° (ICC=0.69).

Conclusions : Our results are consistent with the morphological distribution of photoreceptor types and demonstrate a reasonable reliability of the method in healthy individuals. The method presents an objective and reliable test of local retinal function for different photoreceptors and due to the gaze-controlled and short duration it is easily applicable in clinical trials.

This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.

 

Topographical maps of the relative pupil responses in the cone-specific protocol (left) and rod-specific protocol (right) averaged across the subjects (n=10).