Chromatic Electroretinography in Non-Human Primates using a Novel Algorithm

Abstract

Purpose : To report the development and results of a novel chromatic electroretinography (ERG) algorithm using the RetEvet device (LKC Technologies) on healthy rhesus macaques (Macaca mulatta).

Methods : : An algorithm for chromatic ERG was developed. The general strategy to isolate the short, medium, and long wavelength cone responses was to maximally stimulate each cone cell subtype while suppressing the signal from the other two subtypes. For short wavelength cones, a blue flash on red background was used. Medium wavelength cones were detected by using a green flash on red background. For long wavelength cones, a red flash on blue background was used. Optimization of the suppressing effect of the background light was performed by selecting the background light intensity that maintains b-wave latency near the high-background limit while maximizing the b-wave amplitude. Chromatic ERG was performed on animals with normal eyes confirmed by anterior and posterior segment ophthalmic examination, fundus photography, spectral domain optical coherence tomography, fundus autofluorescence, and standard full-field scotopic and photopic ERG testing. Reported values, after excluding statistical outliers, are averages +/- standard error of the mean.

Results : The algorithm developed for relative isolation of the short, medium and long wavelength cone responses resulted in three unique waveforms. Chromatic ERG was performed on 14 normal animals. The short wavelength cones had an a-wave of -12.2 µV (+/-0.6 µV) at 14.59 ms (+/- 0.28 ms) and b-wave of 45.2 µV (+/-3.0 µV) at 27.1 ms (+/- 0.5 ms). The medium wavelength cones had an a-wave of -9.1 µV (+/- 0.7 µV) at 16.03 ms (+/- 0.26 ms) and b-wave of 37.7 µV (+/- 3.2 µV) at 27.42 ms (+/- 0.35 ms). The long wavelength cones had an a-wave of -9.8 µV (+/- 0.9 µV) at 15.80 ms (+/- 0.29 ms) and b-wave of 44.8 µV (+/- 3.1 µV) at 30.0 ms (+/- 0.6 ms). These cone subtype measurements were statistically significantly different in each parameter except b-wave amplitude (P = 0.002, 0.02, 0.0003, 0.2 for a-wave time, a-wave amplitude, b-wave time, b-wave amplitude, respectively).

Conclusions : Chromatic electroretinography can be performed successfully in non-human primates using a customized algorithm in conjunction with the RETevet device. Applications of this technique include investigation of color vision in non-human primates as well as response to gene therapy targeting cone photoreceptors.

This is a 2020 ARVO Annual Meeting abstract.