Purpose: To investigate aqueous humor nitric oxide (NO) levels in patients with branch retinal vein occlusion (BRVO) and central retinal vein occlusion (CRVO) and to compare these with age-matched controls.

Methods: Eight consecutive patients with BRVO and 16 patients with CRVO were included in this study. Aqueous humor specimens were obtained within 21 days of diagnosis. Samples of aqueous humor were also collected from 20 control patients undergoing cataract surgery. For each sample after reduction of nitrate to nitrite with vanadium chloride (VCL3), we used spectrophotometric method for simultaneous detection of nitrate and nitrite.

Results: Mean level of aqueous humor nitrite and nitrate were 84.08±21.29 μmol/l in BRVO group, 65.40±22.23 μmol/l in CRVO group, and 55.68±11.02 μmol/l in control group. The difference between aqueous humor nitrite and nitrate levels of BRVO group and that of control group was statistically significant (P<0.0001) but not for the difference between those of CRVO and control groups (P=0.10).

Conclusion: The results may support involvement of nitric oxide in the pathogenesis of BRVO.