Retinal Cell Damage by Exposure to Short-wavelength Light

Abstract

Purpose: : Excessive light causes retinal cell death by apoptosis. Because of the difference in light energy level, the severity of retinal damage may be altered by the wavelength involved in the exposed light. However, the details are not fully understood. In this study, we analyzed the levels of the retinal light damage caused by each wavelength using the filters that block either ultraviolet (UV) light, or UV and blue light.

Methods: : BALB/c male mice (6 to 8 weeks old) were purchased and kept under dim cyclic light (5 lux, 12 h on/off). The mice were dark-adapted by keeping them in complete darkness for 12 hours, before exposure to a white fluorescence lamp for 3 hours (5000 lux). The mice were separated into 3 groups, and exposed to the light through different characteristic filters; control filter, UV light filter, UV-and-blue light filter. The intensity of the light through the filters was confirmed to be equal in each group. The retinal cell damage was evaluated by analyzing the apoptosis with TUNEL assay (2 days after light exposure).

Results: : The number of TUNEL positive cells was significantly decreased both in the UV light filter group and the UV-and-blue light filter group compared to control group. Interestingly, UV-and-blue light filter group showed significantly smaller number of apoptotic cells than UV light filter group.

Conclusions: : Blue light itself, not only UV light, caused significant retinal cell damage by inducing apoptosis. Blocking blue light in addition to UV light was more effective to protect retinal tissue against apoptosis.

Keywords: photoreceptors • retinal degenerations: cell biology • retina: distal (photoreceptors, horizontal cells, bipolar cells)