Abstract
Purpose :
The Royal College of Surgeons (RCS) rat is a prominent photoreceptor degeneration model that is often used to determine the safety and efficacy of prospective age-related macular degeneration and retinitis pigmentosa therapies. We aim to characterize retinal structural and vascular pathologies in RCS rat using visible-light optical coherence tomography (vis-OCT).
Methods :
The retinas of pigmented RCS rats (9 animals) were scanned by a fiber-based vis-OCT system with a 1.7 µm axial resolution, 70 kHz A-scan rate, 100 nm-bandwidth wavelengths centered at 560 nm. The animals were anesthetized with ketamine (80 mg/kg) / xylazine (5 mg/kg) cocktail. Volumetric raster scans were acquired near optic disc at the age of 1 month, 3 months, and 8 months. Each scan contains 256 A-lines in each B-scan, 2 repeated B-scans at each Y-location, and 256 Y-locations in 2×2-mm or 1×1-mm regions. Retinal layers were segmented, and the retinal thickness maps and en face angiograms of inner retina were generated.
Results :
At the age of 1 month, the RCS rats demonstrated normal retinal structure and vasculature. The outer plexiform layer (OPL) and outer nuclear layer (ONL) are clearly visualized from the OCT B-scans (Fig. 1). Nerve fiber bundles and inner retinal vessels with normal densities are demonstrated by their en face images. At the age of 3 months, the ONL disappears indicating the photoreceptor loss. However, the retinal vasculature and nerve fiber bundles appear not be affected by the thinning of retinal tissue. At the age of 8 months, the pathologies progress more dramatically - inner nuclear layer (INL) and OPL also vanish. At this stage, we can see damaged nerve fiber bundles and poor retinal perfusion.
Conclusions :
High resolution OCT and OCTA at visible light band can be used to characterize retinal dystrophy in RCS rats. This preliminary study suggests retinal vasculature could be impaired as a consequence of neuronal cell death.
This is a 2021 ARVO Annual Meeting abstract.