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Masahiko Ayaki, Yoshimi Niwano, Taro Kanno, Kazuo Tsubota; Blue light induces oxidative damage in human ocular surface cells in culture. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):5613.
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Timeless exposure to blue light (visible light with wave length from 400 to 500nm) in modern society raises concern about potential hazard on eye and systemic health since blue light is associated with retinal damage and circadian rhythm disorder in experimental settings. We previously reported phototoxicity of blue light in cultured rabbit corneoconjunctival cells (Br J Ophthalmol 2014). The purpose of this study was to examine phototoxicity and oxidative stress with blue light irradiation of human ocular surface cells.
Primary cell lines of ocular cells were established from eye bank eyes. An aliquot (100 μl) of medium containing approximately 2 x 104 cells was seeded to each well of 96 well-culture plate and incubated for 26-28 hours and 2 days for sub-confluent (20-40%) and 90-100% confluent condition, respectively. After blue light irradiation (405 nm with irradiance of 930 mW/cm2) of these cells for designated time period, the cells were further incubated for 24 hours to determine survived viable cells by the MTT assay. Cell viability was also measured in the wells covered with blue light or UV filters. Intracellular reactive oxygen species (ROS) in 90-100% confluent cells was measured by a DCF assay after 6 minutes irradiation.
In sub-confluent condition, cell viability of central corneal epithelial, peripheral corneal epitheliall, and conjunctival cells significantly decreased after exposure to blue light for 3 minutes compared with control without blue light exposure (P<0.01, Dunnett test). Irradiation time dependency of phototoxicity was confirmed with statistical significance (P<0.05, Dunnett test) using corneal epithelial cells. Blue light and UV filters were effective in protecting the cells from blue light-induced damage. Intracellular ROS was significantly higher in the irradiated cells than in control cells (P<0.01, Student’s t test).
Our results indicated that blue light injured human ocular surface cells with time dependency by inducing oxidative stress and the cells were protected from damage by blue light filter. We speculate that long term exposure to blue light from portable devices hand held in a short distance may cause potential burden on ocular health especially for high risk population such as contact lens user, dry eye, malnutrition, or aging.
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