Investigation of Laser-Induced Retinal Damage.
Annual rept. 1 Apr 91-31 Mar 92,
TEXAS UNIV HEALTH SCIENCE CENTER AT SAN ANTONIO
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Laser-induced, photooxidative damage in ocular tissue was studied with a quantitative assay using high performance liquid chromatography HPLC to separate oxidized and reduced ascorbic acid in exposed tissue components. We demonstrated that ascorbic acid, incubated with whole, bovine retinal pigment epithelial RPE cells, was oxidized when the reaction mixture was exposed to the output of an argon-ion continuous wave laser The amount of ascorbic acid oxidized was proportional to the irradiance of the sample, and the reaction was wavelength-dependent, with short-wavelength visible light more effective than long-wavelengths in driving the, reaction. The photosensitizing activity was associated with the RPE melanin pigment granules, and was not lost after disrupting or heating the RPE cells. Because melanin was known to form free radicals when illuminated, we hypothesized that ascorbic acid detoxified the light-activated melanin free radicals while being itself oxidized in process. If the supply of reduced ascorbic acid were exhausted, however, the activated melanin could have been source of tissue-damaging radicals. This model was consistent with a photochemical damage mechanism involving light-activated melanin.
- Medicine and Medical Research
- Physical Chemistry