ENERGY FLUCTUATIONS IN AN EXCIMER-LASER DURING PHOTOREFRACTIVE KERATECTOMY

We performed an experiment with the MEL 60 excimer laser (Aesculap Med itec Technology) to demonstrate the variations of energy of the laser beam that could happen during a refractive surgical procedure. In orde r to quantify such variations, we measured the whitening of a photogra phic paper after a series of exposures to the laser beam with the X ri te 400 B/W reflection densitometer. The energy fluctuations noted betw een two series of pulses averaged 11.02% (minimum 0; maximum 46). Thes e fluctuations tended to decrease progressively during the procedure. The energy of the laser beam decreased with time. At the end of the ex periment, the total loss of energy was 45.16%. These results suggest t hat clinically meaningful energy variations could happen during the ph otorefractive keratectomy and reduce refractive predictability.