Figure 3. Chronic and acute retinal photodamage in Rdh8^−/−Abca4^−/−mice.

Rdh8^−/−Abca4^−/−mice exhibit severe retinal photodamage due to excess accumulation of all-trans-RAL. Epon-embedded retina cross-section images (A) and in vivo high-definition spectral-domain optical coherent tomography images (B) were obtained from Rdh8^−/−Abca4^−/−mice with chronic and acute photodamage. The disruption of the outer nuclear layer (ONL) with a decreasing number of photoreceptor cells was manifested compared to age-matched Rdh8^+/+Abca4^+/+ mouse retina (A left and middle panels) under regular cyclic light at 4 months of age. In vivo retinal image was obtained from these mice by spectral domain optical coherent tomography (SD-OCT). In Rdh8^−/−Abca4^−/−mice, disruption of ONL was demonstrated in the inferior retina (B upper panel) although Rdh8^+/+Abca4^+/+ retina maintained normal structure (B lower panel). Acute retinal photodamage was induced in Rdh8^−/−Abca4^−/−mice (6 weeks old) by intense light exposure (10,000 lux for 30 min) and retinal cross section images were obtained at 14 days after light exposure. Most of photoreceptors were disappeared and only debris of dead photoreceptor cells were accumulated in the subretinal space (A right panel). SD-OCT image showed only residual ONL layer and debris accumulation as well (white arrows in B middle panel). INL, inner nuclear layer; IS, inner segment; ONL, outer nuclear layer; OS, outer segment. Scale bar in A indicates 40 μm.