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

· Background: Excessive generation of free radicals due to light absorption is proposed as the most likely mechanism for photochemical retinal damage. The observed reduction of green light-induced retinal injury after ascorbate treatment is believed to be an antioxidative effect. The aim of the present study was to evaluate the possible protection of ascorbate against blue light-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 exposure to blue light. After 20–22 h of dark adaptation, two groups of the rats were exposed in pairs to the blue light (400–480 nm) for 6 h at an average irradiance of 0.7 W/m² in the cage. Six days after light exposure, all rats were killed and retinal samples were analyzed. · Results: Diffuse blue light irradiation resulted in an uneven distribution of damage in the retina. As judged from the pathological changes in the retina irradiated, no microscopic difference was observed between the two groups. The preserved thickness 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 significantly different between the two groups. · Conclusion: The ascorbate did not protect the retina from blue-light induced damage. This favors the assumption that the mechanisms for blue light-induced retinal damage might differ from that for green light. Received: 13 October 1998 Revised version received: 22 January 1999 Accepted: 18 February 1999