Aqueous humor nitric oxide levels in patients with central retinal artery occlusion

Background/Purpose: There is increasing evidence suggesting that nitric oxide (NO) is implicated in the pathogenic process of ischemic disease. The purpose of this study was to quantify the aqueous humor NO levels in patients with central retinal artery occlusion (CRAO) and in age-matched controls. Methods: Aqueous humor specimens were obtained from seven patients who had been diagnosed with CRAO; the sampling was done within 12 to 24 hours of diagnosis. All specimens were obtained by paracentesis, which was performed as a therapeutic intervention. Samples of aqueous humor were also collected from 15 age-matched healthy patients undergoing cataract surgery, to be used as controls. For each sample, we assayed the amount of nitrite, which is the stable metabolite of NO, using the spectrophotometric method based on the Griess reaction. Results: There were detectable levels of nitrite in the aqueous humor from five of seven patients with CRAO (mean level, 0.32 +/- 0.08 mu mol/L). The levels in the control group were below the detection limit in all cases (<0.08 <mu>mol/L). There was a statistically significant difference between the aqueous humor nitrite levels in the CRAO group and the controls (P = 0.0008). Conclusions: Our study shows that patients with CRAO present with elevated levels of NO in the aqueous humor. These findings may provide insight into the role that NO plays in CRAO.