Assessing the Impact of Stimulus Parameters on the Pupillary Light Response

Abstract

Purpose : Our previous irregular pupillary response in primary open-angle glaucoma (POAG) investigations revealed that the maximum constriction and dilation speeds may be sensitive biomarkers for detecting POAG independent of the age factor. This study aimed to assess the impact of different stimuli parameters such as luminance, stimulus duration, and wavelength on the pupillary response.

Methods : Fifteen healthy participants (15-25 years) without ocular diseases, irrespective of sex were recruited. Informed consent was obtained. Pupillary responses were recorded using an Eye Link 1000 Plus Eye Tracker in trials involving 5 seconds of a dark background, a flash, and another dark background (total 10 seconds). Participants underwent multiple trials with variations in flash duration (1 and 2 seconds), luminance (100 cd/m² and 145 cd/m²), and wavelengths (blue, red, and white at 145 cd/m² with 1-second flash). Each variation comprised three trials, and average constriction/dilation speeds were computed. The Wilcoxon signed-rank test (two-sided p-value) assessed differences, and ANOVA examined variations in speeds associated with different wavelengths.

Results : Constriction and dilation speeds slightly increased at a longer duration (2s) with lower luminance (100 cd/m²) and decreased at 2s with higher luminance (145 cd/m²). Though not statistically significant (Figures 1.a) and 1.b)), changes suggest a potential ipRGCs saturation effect. White and blue (450 nm) wavelengths displayed similar sensitivity at 145 cd/m² with a 1-second duration, while green (545 nm) showed a non-significant increase, and red (620 nm) a non-significant decrease, aligning with ipRGC sensitivity.

Conclusions : While no statistical significance was found in constriction and dilation speeds across luminance, duration, and wavelengths, the white stimulus at 145 cd/m² for one second or 100 cd/m² for two seconds demonstrated superior sensitivity. These configurations will be utilized in future studies comparing healthy subjects and newly diagnosed, pre-medication POAG cases.

This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.

 

Figure 1. Statistical analyses. a) Maximum constriction speed, 1s and 2s white flash, luminance 100 and 145 cd/m². b) Maximum dilation speed, 1s and 2s white flash, luminance 100 and 145 cd/m². c) Maximum constriction speed at different wavelengths (White, Blue, Green, Red), 1s. (d) Maximum dilation speed at different wavelengths (White, Blue, Green, Red), 1s.