Effect of Ascorbic Acid on Experimental Retinal Vein Occlusion

ABSTRACT

The retinal vein occlusion is one of the most common vision-threatening retinal diseases, and both the hemi-central and central retinal vein occlusion might induce severe visual loss. There have been many studies on the role of abnormally produced oxygen free radicals and excitatory amino acids in the mechanism of ischemic retinal injury. Many free radical scavengers, such as superoxide dismutase (SOD), catalase, and EGB 761 were reported to reduce the extent of ischemic retinal injury in animal experiments. Ascorbic acid is also a well-known free radical scavenger, but its in vivo therapeutic effects on retinal ischemia has not been studied, yet. We induced experimental retinal vein occlusion in 48 albino rat eyes; half of major veins in 24 eyes (group A) and total veins in 24 eyes (group B), with rose bengal dye injection followed by argon-green laser photocoagulation. The occlusion of veins was confirmed with fluorescein angiography. We injected ascorbic acid intraperitoneally just after venous occlusion in 12 eyes for each group. Rats were sacrificed after I week (group A) or 2 weeks (group B) following experiment and histological examination was done. In both groups, inner retina was less damaged than outer retina. The density of retinal ganglion cells was reduced to a less degree in eyes of rats treated with ascorbic acid in group A(P=0.0318). These data support the idea that the reactive free adicals are involved in the mechanism of ischemic retinal injury and thus the ascorbic acid may attenuate the ischemic retinal damage.