Induction of oxidative stress in human aqueous and vitreous humors by Nd:YAG laser posterior capsulotomy.

ABSTRACT

AIM: To evaluate whether the Q-switched NdYAG laser treatment applied in routine capsulotomy elicits oxidative stress in aqueous and vitreous humors. METHODS: Thirty-six patients who had to undergo a 25 gauge pars plana vitrectomy due to vitreoretinal disorders were enrolled, 15 of them underwent a Q-switched NdYAG laser capsulotomy 7d before vitrectomy due to posterior capsule opacification (PCO) (NdYAG laser group) while the remaining 21 patients were not laser treated before vitrectomy (no NdYAG laser group). Samples of the aqueous and vitreous humors were collected during vitrectomy from all patients for the assessment of oxidative parameters which were compared between the NdYAG laser group and no NdYAG laser group. Thiobarbituric acid reactive substances (TBARS), a product of membrane lipid peroxidation, nitrite levels, the antioxidative activities of SOD and catalase, the 4-HNE-protein conjugate formation, indicating structural modifications in proteins due to lipoperoxidation, were assessed in aqueous and vitreous samples. RESULTS: In the human vitreous humor TBARS levels are significantly higher in the NdYAG laser group compared to the no NdYAG laser group and importantly, there is a significant correlation between the TBARS levels and the total energy of NdYAG laser used during capsulotomy. Moreover the anti-oxidative activities of SOD and catalase were significantly decreased by NdYAG laser treatment, both in aqueous and vitreous humors. In accordance with the TBARS data and anti-oxidative enzyme activities, significantly higher levels of proteins were conjugated with the lipoperoxidation product 4-HNE in the aqueous and vitreous humors in the NdYAG laser-treated group in comparison to no NdYAG laser group. CONCLUSION: These data, clearly suggest that any change that Q-switched NdYAG photo disruption may cause in the aqueous and vitreous compartments, resulting in a higher level of oxidative damage might be of considerable clinical significance particularly by accelerating the aging of the anterior and posterior segments of the eye and by worsening the intraocular pressure, the uveal, the retinal (especially macular) pathologies.