Typical pathomorphologic changes were observed in the retinas of light-exposed rats (
Fig. 1A). Control retinas had a uniform appearance with intact, evenly spaced RPE and well-aligned, compact photoreceptor outer segments, and all photoreceptor cell bodies exhibited uniformly stained chromatin occupying the entire soma. At varying times after light exposure, normal RPE thickness (
X̄ = 2.8 μm ± 0.1 μm [SEM]), ONL thickness (
X̄ = 34 μm ± 0.8 μm [SEM]), or photoreceptor segment length (
X̄ = 23 μm ± 0.5 μm [SEM]) measured in control rats was reduced in rats exposed to blue light (
Fig. 1B). After this light exposure, damage occurred primarily to the superior-temporal retina. Blue light exposure resulted immediately in vacuolization in the RPE, pyknotic cells with condensed chromatin in the ONL, and swelling of the ONL and photoreceptor inner segments (
Fig. 1A). By 24 hours after light exposure, at least 40% of the cells in the ONL were pyknotic, necrotic, or both; in addition, IOS were disorganized, and IOS length was significantly reduced (
P < 0.05) by 21% compared with IOS thickness in control rats not exposed to blue light (
Fig. 1B). Forty-eight hours after light exposure, RPE thickness was reduced 26%, ONL thickness was reduced 27%, and IOS length was significantly reduced by 38%. By 7 days after blue light exposure, patchy loss of RPE cells was observed, ONL thickness was significantly reduced by 35%, and IOS length was reduced by 60% compared with normal. No significant INL lesions were detected in rats receiving 6-hour blue light exposure at any postexposure times evaluated.