Association of flickering chromatic pupillometry with functional and structural tests in patients at risk for open-angle glaucoma

Abstract

Purpose: Chromatic pupillometry assesses human retinal function by measuring pupil responses to different colored light stimuli. This technique allows the study of retinal and optic nerve diseases, such as open-angle glaucoma (OAG). However, the diagnosis of early OAG remains a challenge. We hypothesize that flickering chromatic pupil responses are associated with pattern electroretinography (PERG) and optical coherence tomography (OCT) parameters in patients at risk for OAG. Methods: Twenty OAG-risk patients participated in this study, characterized by clinical and risk factors indicating an increased likelihood of developing OAG. Pupillary recordings were obtained using a lab-made photostimulator-pupillometer system with monochromatic stimuli of blue (468 nm), green (516 nm), and red (632 nm). Sinusoidal stimuli (frequency=1Hz, duration=10s) were presented monocularly at two modulation levels: 100% and 70%. Amplitude and phase were assessed in the frequency domain. The PERG recordings were obtained following a contrast sensitivity protocol, black-white alternating bars stimuli (reversal frequency=15Hz, duration=25s) at two contrasts:100% and 85%. Magnitude (M), MagnitudeD (MD), and MagnitudeD/Magnitude ratio (MD/M) were analyzed. Spectral-domain optical coherence tomography (OCT) scans were performed to obtain retinal nerve fiber layer thickness (RNFL), ganglion cell complex thickness (GCC), and optic nerve head parameters. Results: Blue pupil amplitude was significantly associated with MD (r=0.55; p<0.05). Red pupil amplitude was correlated with MD/M (r=0.51; p<0,05). The GCC thickness was associated with the green pupil amplitude (r=0.47; p<0.05). The RNFL thickness was correlated with red pupil amplitude (70%: r=0.53; p<0.05; 100%: r=0.50; p<0.05). The red pupil phase was associated with the cup area (70%: r=0.52; p<0.05. 100%: r=0.74; p<0.01) and with the cup-disc area (70%: r=0.56; p<0.05. 100%: r=0.65; p<0.01). Conclusions: Pupillary responses were associated with PERG and OCT parameters in patients at risk for OAG. These results suggest that pupillary amplitude decreases with decreasing ganglion cell activity and RNFL thickness. Our study suggests the ability of chromatic pupillometry to assess early OAG changes. A longitudinal study would allow us to identify the parameters that detect these changes earlier.