Measuring electroretinograms in tree shrews with a portable electrophysiology device.

PURPOSE: The RETeval portable flash electrophysiology device is extensively used for assessing retinal function in humans. However, its utility in measuring electroretinograms in preclinical studies has been less explored. Tree shrews (small diurnal mammals closely related to primates) are a well-established animal model of emmetropization known to exhibit robust responses to visual cues and mimic human juvenile-onset myopia. This study aimed to evaluate the intra- and inter-session repeatability of full-field photopic electroretinograms (ERGs) recorded using the RETeval system in tree shrews.

METHODS

At 24 ± 1 days of visual experience (DVE), twelve juvenile tree shrews housed in broadband colony light (100-300 lx) underwent electrophysiology testing of the normally developing eye using the RETeval system (LKC Technologies, MD, USA). Measurements were repeated twice in each session, as well as at 30 and 35 DVE. The amplitudes and peak times of the flash, flicker, photopic negative response, S-cone, and On-Off ERGs were analyzed. The intra- and inter-session repeatability was assessed using the coefficient of variation (CoV), intra-class correlation coefficient (ICC), mean bias (%), paired t-test, and Bland-Altman analysis.

RESULTS

Tree shrew ERGs exhibited well-defined and robust waveforms comparable to those of human ERGs. Flash and flicker ERGs showed excellent intra-session repeatability for both amplitudes and peak times (CoV < 5%, mean bias ≤ 5%, and ICC ≥ 0.98). While the ERGs were also repeatable across different sessions, the repeatability metrics were comparatively better for peak times (CoV: < 10%, mean bias: < 15%) than for amplitudes (CoV: 13.36-29.35%, mean bias: 18.89-41.51%) with ICC values between 0.4 and 0.86 for inter-session ERGs, indicating modest repeatability.

CONCLUSIONS

The RETeval measurements of full-field photopic ERGs in tree shrews were robust and reliable, with waveforms morphologically similar to human ERGs, demonstrating the utility of the RETeval system in measuring retinal function in this species. The photopic ERGs were repeatable across sessions on different days, indicating the feasibility of using this device in longitudinal studies of retinal function in tree shrews, for example, in studying the neural basis of emmetropization.