Abstract
Purpose: :
Endoillumination for using an operating microscope during ophthalmic surgeries (e.g. vitrectomy) may be responsible for retinal damage. In spite of wide recognition that endogenous antioxidants in the vitreous such as ascorbic acid (vitamin C) are pivotal in protecting the retina from light toxicity, artificial aqueous humors used during ophthalmic surgeries contain only gulthathion as an antioxidant. We hypothesize that induction of vitamin C to the aqueous humors may contribute to preserve retinal integrity. Using isolated rat retinas, we evaluated the effect of vitamin C on acute light toxicity. The retinal damage was assessed by morphological examination and measuring amounts of lactate dehydrogenase (LDH) release from injured cells.
Methods: :
Male Sprague–Dawley rats (PND 30 ± 2) were anesthetized and decapitated for enucleation. After removal of the vitreous the sensory retinal tissue was gently detached from the retinal pigment epithelium. In the presence or absence of vitamin C (1 or 3 mM), the retinas kept in a vial with medium were exposed to UVB (302 nm) for 1 hour and post–incubated at 30ºC. Small amount of medium were sampled from each vial every 1 hour for spectrophotometrical determination of LDH activities. After 5 hour postincubation retinas were homogenized to determine the total LDH activities. Other retinas were fixed for light microscopical analysis.
Results: :
Without vitamin C LDH release was significantly increased after UV exposure if compared with control at any hour after the post–incubation. With 1 mM vitamin C, LDH release after UV exposure was significantly reduced during the post–incubation period. No difference was found between effects of 1mM and 3 mM vitamin C. Microscopical examination revealed that disorganization in the outer nucleous layer after UV exposure was attenuated by administration of 1 mM vitamin C.
Conclusions: :
One mM vitamin C, a concentration found in the anterior chamber in human, prevented phototoxic injury following UV exposure. Addition of vitamin C in artificial aqueous humors may be beneficial to avoid intraoperative light toxicity.
Keywords: retina • oxidation/oxidative or free radical damage • antioxidants