Spectral domain optical coherence tomography analysis of the retina in a rat model: a comparison of transgenic immunodeficient retinal degenerate rat (SD-Foxn1 Tg(S334ter)3Lav) and rats with normal retina

Abstract

Purpose: Retinal degeneration (RD) affects millions of people worldwide, and in vivo monitoring of the progression of this disorder is needed to aid the development of treatments for it, such as retinal sheet transplants. The goal of this study is twofold: to show that retinal degeneration worsens with age, and to demonstrate that Spectral Domain Optical Coherence Tomography (SD-OCT) can track the progression of this condition in a new immunodeficient RD rat model.

Methods: Retinal cross-section SD-OCT scans (Bioptigen Envisu R2200 Spectral Domain Ophthalmic Imaging System) were obtained from male and female rats (n=40) aged between P17-P77, using a group of transgenic SD-Foxn1 Tg(S334ter)3Lav rats (=RD rats) as a model for retinal degeneration, and a normal retinal control group of rats expressing human placental alkaline phosphatase (hPAP). Data analysis was done using the Bioptigen post-scan analysis software InVivoVue Diver Release 2.0 (Bioptigen, Research Triangle Park, NC). Changes in the thickness of the total retina (TR), the outer retina (OR), and the inner nuclear layer (INL) were determined with respect to age. Using SigmaPlot 11.0 (Systat Software, Inc., San Jose, CA; Fisher-corrected multiple comparison tests), layer thicknesses were compared with age group and with rat strain.

Results: P17 was the earliest age in which retinas could be imaged. At this age, there was already a noticeable difference in total retinal (TR) and outer retinal (OR) thickness between hPAP rats and RD rats. In normal rats, TR was decreasing with eye growth between the ages of P17 and P77 by 10.4% (from 260μm to 233μm) whereas TR of RD rats decreased by 32.6% (from 133μm to 95μm). OR was decreasing with eye growth between the ages of P17-P77 by 6.5% (from 141μm to 132μm) whereas OR of RD rats decreased by 28.8% (from 26μm to 20μm). The INL was decreasing with eye growth between the ages of P17-P77 by 32.6% (from 38μm to 25μm) whereas the INL of RD rats decreased by 38.8% (from 34μm to 21μm).

Conclusions: This study has demonstrated that SD-OCT is a viable method of detecting and analyzing retinal degeneration; and consequently, the status of the retina and any occurring changes can be monitored and analyzed over time in vivo. SD-OCT may be useful in the evaluation of treatments for retinal degeneration.