Altered retinal responses in chicken myopia model using image-guided global flash multifocal electroretinogram

Abstract

Purpose : Myopic humans and chickens showed abnormal electroretinogram (ERG), but the contribution of individual retinal regions to this change remains unclear. This study aimed to test a global flash multi-focal ERG (MOFO mfERG) protocol intended to differentiate the inner and outer retinal contributions using an image-guided approach in chicks developing high myopia.

Methods : Twenty White Leghorn chicks (Gallus gallus domesticus) were randomly assigned to wear spherical lenses (-10DS, “LIM”, n=10) monocularly or left untreated (“control”, n=10) from post-hatching day 5 (P5) to day 12 (P12). Refraction, A-scan ultrasonography, and MOFO mfERG were performed at P12. While chicks were anesthetized, retinal responses were recorded using the MOFO mfERG protocol with the aids of a scanning laser ophthalmoscope (RETIscan, Germany). This protocol allowed real-time monitoring of visual stimuli delivered to target retinal region. The visual stimulus matrix consisted of 61 unscaled hexagons covering a total of ~30° visual angle. As a first approach, MOFO responses were grouped into central, mid-peripheral and peripheral regions for analysis. The amplitudes and implicit times of the direct (DC) and indirect components (IC) were compared between treatment and control group.

Results : One week of -10D lens wear in the treatment group induced significantly high magnitudes of myopia than the control group (LIM= -9.07±0.45D, control= +0.04±0.14 D; two sample t-test, p<0.001). Compared to control group, the treatment group showed significant reductions in IC component in both central (LIM= 3.38±0.52 nV/deg², Control= 6.22±0.82 nV/deg²; two sample t-test,p=0.01) and mid-peripheral retinal regions (LIM= 2.01±0.27 nV/deg², Control= 3.49±0.36 nV/deg²; two sample t-test, p<0.01). No other differences were found in the amplitude of DC and implicit times of DC or IC components between the two groups (p>0.05). Pearson’s correlation analysis revealed significant correlations between the spherical equivalent and IC amplitudes in central (r=0.60, p<0.01) and mid-peripheral regions (r=0.61, p<0.01).

Conclusions : Our results show, for the first time, that lens-induced myopia is associated with a reduction of inner retinal component at specific retinal regions in chicks. Further studies are needed to determine the origin of these altered retinal responses.

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