Increase of free oxygen radicals in aqueous humour induced by selective Nd: YAG laser trabeculoplasty in the rabbit

PURPOSE. To investigate the impact of selective Nd:YAG laser trabeculoplast y on free oxygen radicals and antioxidant enzymes of the aqueous humour in the rabbit. METHODS. One eye of 18 rabbits was subjected to 360 degrees selective laser trabeculoplasty (LT) with a frequency-doubled Nd:YAG laser (532 nm). The a nterior chamber aqueous humour was aspirated 3, 12 hours and 1, 3, 7, 10 da ys after treatment. Lipid peroxide (LPO) and glutathione S transferase (GST ) levels and superoxide dismutase (SOD) activities of aqueous humour were m easured. RESULTS. Concentrations of LPO in the aqueous humour of the treated eyes we re significantly higher than the untreated eyes until the 7th day. Aqueous SOD activity significantly decreased 3 hours after LT and remained low unti l day 7. Aqueous GST levels were significantly decreased between 12 hours a nd 7 days after the LT. CONCLUSIONS. Selective LT was followed by an immediate increase in the aque ous humour LPO concentration and decreases of SOD and GST in the rabbit, pr obably due to photo-vaporization and photodisruption caused by the frequenc y- doubled Nd:YAG laser. The increased aqueous LPO levels suggest that free oxygen radicals are formed in the pigmented trabecular meshwork during LT, and may be responsible for the inflammatory complications of this procedur e.