Analysis of Changes in Retinal Photoreceptors Using Optical Coherence Tomography in a Feline Model of Iodoacetic Acid-induced Retinal Degeneration

Abstract

PurposeWe investigated structural changes in the retina by using optical coherence tomography (OCT) in a feline model of retinal degeneration using iodoacetic acid (IAA).MethodsWe examined 22 eyes of 11 felines over 2 years of age. The felines had fasted for 12 hours and were intravenously injected with IAA 20 mg/kg of body weight. OCT (Spectralis OCT) was performed at the point where the ends of the retinal vessels collected in the lateral direction from the optic nerve head and area centralis. Similarly, OCT was performed four times at 1-week intervals following injections, at which point the felines were sacrificed and histologic examinations were performed. Using OCT, the thickness of each layer of the retina was measured.ResultsThe average body weight of the three male and eight female felines investigated in this study was 1.61 ± 0.19 kg. The mean total retinal thickness of the felines before injection was 221.32 ± 9.82 µm, with a significant decrease in the retinal thickness at 2, 3, and 4 weeks following injections of 186.41 ± 35.42, 174.56 ± 31.94, and 175.35 ± 33.84 µm, respectively (p = 0.028, 0.027, and 0.027, respectively). The thickness of the outer nuclear layer was 57.49 ± 8.03 µm before injection and 29.26 ± 17.87, 25.62 ± 13.88, and 31.60 ± 18.38 µm at 2, 3, and 4 weeks, respectively, after injection (p = 0.028, 0.028, 0.046, respectively).ConclusionsIn a feline model of retinal degeneration using IAA, the total retinal thickness and the thickness of the outer nuclear layer were shown to decrease significantly on OCT.

Chemically induced cone degeneration in the 13-lined ground squirrel

“…Transient increases in choroidal thickness were also observed in the IAA, ATP, and SNP groups, although fluctuation in thickness was present within all groups. Variation in the response to chemical administration and the extent of the damage have also been observed in other models of chemically induced degeneration, including IAA and ATP studies in felines (Aplin et al, 2014;Myeong Noh et al, 2019), IAA studies in 13-LGS (Farber et al, 1983), ATP studies in rats (Vessey et al, 2014), SNP studies in rabbits (Li et al, 2018), and Tm studies in guinea pigs and ground squirrels (California and 13-LGS) (Anderson et al, 1988;Spencer et al, 2020). While the variability was not always directly referenced, studies that did highlight variable observations speculate these discrepancies arose from a range of sources, such as differences in injection procedure, differences in intraretinal diffusion, and insensitive assessments (Anderson et al, 1988;Li et al, 2018).…”