Effects of ascorbic acid on UV light-mediated photoreceptor damage in isolated rat retina

Concerns have been raised about whether operating microscopes and endoillumination used during ophthalmic surgeries contribute to retinal damage. Despite the recognition that ascorbic acid (vitamin C) helps to protect the eye from light and the abundance of vitamin C in the retina, artificial aqueous humors used during surgery only contain the antioxidant glutathione. To test whether inclusion of antioxidants other than glutathione in surgical solutions might help to preserve retinal integrity, we studied the effects of vitamin C on acute toxicity in isolated rat retinas. Male Sprague-Dawley rats (PND 30 ± 2) were sacrificed for retinal isolation. In the presence or absence of vitamin C (1 or 3 mM), retinas were exposed to 302 nm ultraviolet B (UVB) light for 1 h and were incubated for a total of 5 h at 30 °C. Retinal damage was assessed by morphological examination and biochemical assay measuring the amount of lactate dehydrogenase (LDH) released from injured cells. In control retinas, LDH release was significantly increased after UVB exposure. The presence of 1 mM vitamin C in the incubation media significantly reduced LDH release during the post-incubation period following UV exposure. No difference was found between 1 and 3 mM vitamin C. Microscopic examination revealed that disorganization in the outer nuclear layer after UVB exposure was markedly attenuated by administration of 1 mM vitamin C. Vitamin C (1 mM), a concentration found in the anterior chamber in humans, but not glutathione, prevented phototoxic injury following UV exposure. Although vitamin C itself cannot be used in intraocular irrigating solutions because of adverse interactions with iron released during bleeding, inclusion of antioxidants equivalent to vitamin C should be considered to help protect the retina from intraoperative light toxicity.