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Ocular ischemia and the effects of allopurinol on functional recovery in the retina of the arterially perfused cat eye.

PURPOSE
This study sought to examine the acute effects of ocular ischemia and reperfusion on retinal function and determine the extent to which recovery during reperfusion is improved by allopurinol (AP), a blocker of xanthine oxidase (XO). The latter is presumed to be a major factor in the formation of free radicals associated with reperfusion of ischemic tissue.


METHODS
Electroretinographic (ERG) responses were recorded simultaneously from the two isolated, arterially perfused eyes obtained from the same cat. One eye served as the control and received only the standard perfusate; the other eye was infused with AP before and after a 3 hr period of total ischemia.


RESULTS
After the prolonged period of nonperfusion, recovery of the electroretinographic components was incomplete to varying degrees. Maximum b-wave amplitudes recovered only to 17 +/- 5% (mean +/- SEM) of baseline, whereas the a-wave grew to 60 +/- 10% of its baseline value. For both measures, the recovery of electroretinographic amplitude was significantly greater in AP-treated eyes than in the control eyes.


CONCLUSION
Generation of free radicals by XO contributes to the retinal damage and loss of function that occurs after a period of ischemia and subsequent reperfusion.