Short-term oxidative status of lens and aqueous humor after excimer laser photorefractive keratectomy

PURPOSE: Oxidation in the anterior ocular segment is associated with cataractogenesis and possible complications to corneal endothelium, We investigated whether oxidation occurred in the rabbit anterior ocular segment shortly after excimer laser photorefractive keratectomy (PRK). METHODS: Rabbits were treated unilaterally with PRK, the other eye serving as a control. Aqueous humor sampled shortly after treatment was assayed spectrophotometrically for hydrogen peroxide using ferrous oxidation in xylenol in the presence (group 1; n=10), or absence of oxygen (group 2; n=8). Oxidized glutathione and malondialdehyde levels were measured in lenses by spectrophotometry and HPLC. RESULTS: Hydrogen peroxide concentration of aqueous humor was not different between treated (77 +/- 36 mu M) and control eyes (88 +/- 34 mu M) in the oxygen group or the nonoxygenated group (treated eyes: 6.7 +/- 5.4 mu M and control eyes: 5.5 +/- 4.7 mu M). Peroxide levels did not correspond to endogenous H2O2 but presumably reflected action on ascorbic acid. There was no difference in the percent of oxidized glutathione between experimental and control eyes. Malondialdehyde could not be detected in the lens of treated or control eyes, despite good sensitivity in recovery assays. CONCLUSION: Based on these assays, there is no evidence that PRK oxidizes the aqueous humor or the lens of treated rabbits within 10 minutes of treatment.