[Influence of 460-480 nm wavelength light at three different irradiance on retina tissue of SD rats]

Abstract

Objective: To investigate the survival of SD rat retinal cells after irradiated with 460-480 nm wavelength blue light at three different irradiance.

Methods: Experimental study. Seventy-six SD rats six weeks old were divided into control group (4 animals) and experimental groups (18 different subgroups) with 4 animals for each group. Healthy SD rats were exposed to the 460-480 nm blue light for 3 or 12 hours on three different irradiance of 0.6, 1.5 and 10.0 W/m(2) respectively. After recovery in darkness for 4 hours, 24 hours or 3 days, retinal tissue was collected after the eyes were enucleated. Hematoxylin-eosin staining was performed to evaluate the general anatomical changes of the rat retinal layers. TdT-mediated dUTP nick-end labeling was performed to detect apoptotic cells and immunofluorescence staining was conducted to illustrate the expression and location of related proteins in Müller cells. The number of ganglion cells was analyzed by one-way ANOVA.

Results: No injury was observed in SD rat retina at the irradiance of 0.6 W/m(2). Retinal cells were damaged with irradiance at 10.0 W/m(2), which mainly affected photoreceptors and retinal pigment epithelial cells, while Müller cells of retinal inner nuclear layer were also involved. Apoptosis began after 4 hours of exposure and peaked at 24 hours. Moderate damage of retina was observed at the irradiance of 1.5 W/m(2) after 12 hours rather than 3 hours exposure. The number of ganglion cells was significantly different among the different groups 3 days after exposure. When the exposure time was 3 hours, the number of retinal ganglion cells under different irradiance at 0.0, 0.6, 1.5 and 10.0 W/m(2) was respectively 41.42 ± 0.17, 40.58 ± 0.50, 40.92 ± 0.32 and 22.83 ± 0.79 (F = 1305.86, P = 0.000). When the exposure time was 12 hours, the number of retinal ganglion cells under different irradiance at 0.0, 0.6, 1.5 and 10.0 W/m(2) was respectively 41.42 ± 0.17, 40.83 ± 0.69, 41.08 ± 0.17 and 22.75 ± 0.83 (F = 1095.78, P = 0.000). The number of retinal ganglion cells showed significant decrease 3 days after exposure at the irradiance 10.0 W/m(2) (exposure time 3 h:t = 52.32, P = 0.000; exposure time 12 h:t = 47.58, P = 0.000).

Conclusions: The safe exposure time to SD rat retina layers is 12 hours for the blue light with wavelength 460-480 nm at the irradiance 0.6 W/m(2). And the safe exposure time descends to 3 hours at the irradiance 1.5 W/m(2).