PRK and LASIK - Their potential risk of cataractogenesis: Lipid peroxidation changes in the aqueous humor and crystalline lens of rabbits

Purpose. There are insufficient data on the possible cataractogenic side ef fects of excimer laser corneal surgery. Higher malondialdehyde (MDA) levels could indicate oxidative events related to the cataractogenic process. We therefore examined MDA levels after refractive laser surgery, Methods. Six white Russian rabbits received laser in situ keratomileusis (LASIK) (Schwin d keratome) in the right eye and a 250-mu m-deep microkeratome cut (Schwind microkeratome) in the left eye. Six others underwent photorefractive kerat ectomy (PRK) in the right eye; the left eye remained untreated. The 180 mJ/ cm(2) fluence applied at a rate of 10 Hz with an optical zone diameter of 5 mm in all rabbits (438 pulses) resulted in an estimated central photoablat ion depth of 116 mu m. Two weeks later, lenses and aqueous were taken immed iately after death. MDA was detected in aqueous and homogenate of lenses af ter reacting with thiobarbituric acid (TBA), MDA bound to TBA (MDA-TBA) was specifically analyzed by high-performance liquid chromatography (HPLC) (ex citation, 525 nm; emission, 551 nm) using phosphate-buffered methanol as el uent. Results. No significant laser-induced MDA alteration was found in eit her the aqueous or the lens. The microkeratome group, however, had two to t hree times higher MDA levels in the lenses than the control group (p = 0.12 ) or the PRK (p = 0.03) group. Conclusion, Elevation of MDA in the lens of the microkeratome group indicates that LASIK, but not PRK, may be a risk fa ctor in cataractogenesis. The increased MDA levels in the LASIK group are p robably caused by the microkeratome incision rather than the secondary radi ation of the excimer laser. Postoperative inflammation may explain the surp rising results.