Abstract
PurposeTo evaluate the correlation between optical coherence tomography (OCT) and the histological, ultrastructural and electroretinography (ERG) findings of retinal degeneration in Royal College of Surgeons (RCS-/-) rats.Materials and MethodsUsing OCT, we qualitatively and quantitatively observed the continual retinal degeneration in RCS-/- rats, from postnatal (PN) day 17 until PN day 111. These findings were compared with the corresponding histological, electron microscopic, and ERG findings. We also compared them to OCT findings in wild type RCS+/+ rats, which were used as controls.ResultsAfter PN day 17, the hyperreflective band at the apical side of the photoreceptor layer became blurred. The inner segment (IS) ellipsoid zone then became obscured, and the photoreceptor IS and outer segment (OS) layers became diffusely hyperreflective after PN day 21. These changes correlated with histological and electron microscopic findings showing extracellular lamellar material that accumulated in the photoreceptor OS layer. After PN day 26, the outer nuclear layer became significantly thinner (P < 0.01) and hyperreflective compared with that in the controls; conversely, the photoreceptor IS and OS layers, as well as the inner retinal layers, became significantly thicker (P < 0.001 and P = 0.05, respectively). The apical hyperreflective band, as well as the IS ellipsoid zone, gradually disappeared between PN day 20 and PN day 30; concurrently, the ERG a- and b-wave amplitudes deteriorated. In contrast, the thicknesses of the combined retinal pigment epithelium and choroid did not differ significantly between RCS-/- and RCS+/+ rats.ConclusionOur results suggest that OCT demonstrates histologically validated photoreceptor degeneration in RCS rats, and that OCT findings partly correlate with ERG findings. We propose that OCT is a less invasive and useful method for evaluating photoreceptor degeneration in animal models of retinitis pigmentosa.
Highlights
Retinitis pigmentosa (RP) is the most common hereditary retinal photoreceptor degenerative disease; more than 60 mutated genes have been identified that can cause RP (RetNetTM, Retinal Information Network: https://sph.uth.edu/retnet/home.htm)
Because of its similarity to previously reported histological and ultrastructural findings [4], as well as the absence of the interdigitation structure in the Royal College Surgeons (RCS)-/- rats (Fig 6) [4], we concluded that this apical hyperreflective band was different from the interdigitation zone, and that it corresponded to the accumulated extracellular lamellar material
We reasoned that the basally located band corresponded to the inner segment (IS) ellipsoid zone, because it was similar to the bands observed in the wild type rats and because it corresponded with histological findings that showed an intact ellipsoid zone (Fig 3)
Summary
Using OCT, we qualitatively and quantitatively observed the continual retinal degeneration in RCS-/- rats, from postnatal (PN) day 17 until PN day 111. These findings were compared with the corresponding histological, electron microscopic, and ERG findings. We compared them to OCT findings in wild type RCS+/+ rats, which were used as controls. Data Availability Statement: All relevant data are within the paper and its Supporting Information files. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript
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