A possible mechanism for transpupillary thermotherapy: nitric-oxide-related cellular damage.

Background: To determine the oxidative stress markers on rabbit vitreous following transpupillary thermotherapy (TTT) application.

Methods: The pigmented rabbit eyes were divided into 3 groups, each containing 6 eyes. Group 1 was used as a control group. Twelve eyes underwent TTT with a power of 250 mW (group 2) and 800 mW (group 3), with a diameter of 3000 microm and duration of 60 s; 24 h after laser application, vitreous samples were collected. Nitric oxide (NO) and malondialdehyde (MDA) levels and superoxide dismutase (SOD) activities were determined in all groups.

Results: NO levels were statistically significantly higher in all groups when compared with the control group (p < 0.05). MDA levels were higher and SOD activities were lower in all groups when compared with the control group, but the differences were not significant statistically (p > 0.05).

Interpretation: Our results support the hypothesis that TTT application induces NO synthesis, which may lead to occlusion at choroidal neovessels. Because of the nonsignificantly increased levels of MDA and decrease of SOD activities there maybe only a weak relation between lipid peroxidation induced by free oxygen radicals and TTT-induced vascular damage.