Failure of ascorbate to protect against broadband blue light-induced retinal damage in rat

Background: Excessive generation of free radicals due to light absorption i s proposed as the most likely mechanism for photochemical retinal damage. T he observed reduction of green light-induced retinal injury after ascorbate treatment is believed to be an antioxidative effect. The aim of the presen t study was to evaluate the possible protection of ascorbate against blue l ight-induced photoreceptor damage. Methods: Cyclic light-reared albino rats were injected intraperitoneally with either ascorbate (1 mg/g body weight) or, as placebo, physiological saline 24 h before and just prior to exposur e to blue light. After 20-22 h of dark adaptation, two groups of the rats w ere exposed in pairs to the blue light (400-480 nm) for 6 h at an average i rradiance of 0.7 W/m(2) in the cage. Six days after light exposure, all rat s were killed and retinal samples were analyzed. Results: Diffuse blue ligh t irradiation resulted in an uneven distribution of damage in the retina. A s judged from the pathological changes in the retina irradiated, no microsc opic difference was observed between the two groups. The preserved thicknes s of the outer nuclear layer was on average 61.3% in the ascorbate-treated and 66.4% in the placebo-treated group. The photoreceptor loss was not sign ificantly different between the two groups. Conclusion: The ascorbate did n ot protect the retina from blue-light induced damage. This favors the assum ption that the mechanisms for blue light-induced retinal damage might diffe r from that for green light.