Electron paramagnetic resonance spectroscopy of free radicals in corneal tissue following excimer laser irradiation

Electron paramagnetic resonance spectroscopy (EPR) has been used to examine free radical formation during corneal tissue photoablation. Bovine corneal strips were frozen in liquid nitrogen, irradiated with excimer laser pulses, and assayed by EPR. Exposure conditions were varied to study radical formation dependence on laser intensity and repetition rate. Results were measured against a quantifiable standard to calculate radical quantum yield. EPR measurements indicate that corneal radical formation is largely a photochemical process driven by the 193 nm laser radiation. Reactive radical species are produced in substantial numbers, and likely have a significant clinical role.