Elevated Retinal Thresholds With a Subretinal Microelectrode Array in a Rabbit Model of Photoreceptor Degeneration

Abstract

Purpose: : To study the electrophysiological changes in the neurosensory retina (NSR) and the response in the visual cortex of rabbits following iodoacetic acid (IAA) injection causing photoreceptor degeneration.

Methods: : Adult Dutch–belted rabbits were injected intravenously with IAA (20 mg/kg body weight). The electrodes for visual evoked potentials (VEP) and electrical evoked potentials (EEP) were placed on the dura mater overlying the visual cortex. A stroboscope generated the stimulation for the VEP and a 5x5 microelectrode array (MEA), placed in the subretinal space, provided the stimulus for the EEP. Both VEP and EEP were recorded 14 days, 1 month, 3 months and 6 months after IAA injection. Normal rabbits were used as controls.

Results: : The VEP amplitude was significantly diminished after IAA injection compared to control eyes (normal = 260.5 ± 75.1 µV). The lowest amplitude was observed at 14 days (49.7 ± 21.5 µV); however, a statistically significant recovery was observed at 1 month (204.3 ± 127.8 µV), 3 months (179.7 ± 101.0 µV), and 6 months (203.1 ± 41.1 µV). The EEP threshold significantly increased over time after IAA injection (e.g., at 1 month = 53.1 ± 17.9 nC) compared to controls (9.2 ± 2.9 nC) but recovered over time (e.g., at 6 months = 37.5 ± 19.1 nC). Likewise, the VEP amplitude in these eyes showed recovery over the 6 months time interval (control = 345.2 ± 46.1 µV; 1 month = 138 ± 46.7 µV; 6 months = 355 ± 151.9 µV).

Conclusions: : IAA significantly elevated the retinal threshold in a rabbit model of photoreceptor degeneration using a subretinal MEA to elicit an EEP. However, the electrophysiological changes caused by IAA at the dosage used appear to be transient and reversible.

Keywords: electrophysiology: non-clinical • photoreceptors • retinal degenerations: cell biology