Temporal Changes in Autofluorescence Following Retinal Light Damage in Mice

Abstract

Purpose:: To determine the temporal changes in autofluorescence (AF) following light-induced retinal degeneration in mice using in vivo imaging.

Methods:: In this study, we used wild-type mice (mixed C57/Bl6-SV129 background) homozygous for the Rpe65Leu450 variant. Following overnight dark adaptation, animals were exposed to 13 klux for 2 h. Retinal damage and the degree of AF was assessed with SLO imaging (HRA I, Heidelberg Engineering, Germany) using two different wavelengths (488 nm and 795 nm) and respective barrier filters (BF, 500 nm and 800 nm). Initially, a time course was obtained for a postexposure period (PE) of up to 70 days. In a second experiment, additional data was obtained for a PE of 5 and 30 days. The study was performed in accordance with the ARVO Statement for the Use of Animals in Ophthalmic and Visual Research.

Results:: In previous work, we could show that the light exposure protocol used here leads to the degeneration of photoreceptor outer segments already one day following the light insult. The remaining material was found to be initially associated with a high degree of AF in the short wavelength range (SWR, using a BF of 500 nm), which peaks at about PE 5. Over time, AF in the SWR decreased slowly, whereas AF in the long wavelength range (LWR, using a BF of 800 nm) was absent at PE 5, but developed later with a maximum at about PE 30. A second experiment focussing on the PE 5 and PE 30 time points confirmed these findings.

Conclusions:: The temporal changes in autofluorescence following light-induced retinal degeneration were described in mice using SLO in vivo imaging. Whereas SWR AF was almost immediately present after the light exposure, LWR AF developed only slowly. It may thus be hypothesized that the SWR AF originates predominantly from unprocessed photoreceptor debris, whereas the LWR AF may represent rather processed material, in which the (chemical) modification has altered the fluorescence characteristics.

Keywords: retina • imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • photoreceptors