DEVELOPMENT OF AN ALGORITHM FOR CORNEAL RESHAPING WITH A SCANNING LASER-BEAM

The corneal-ablation rate, the beam-intensity distribution, and the in itial and the desired corneal topographies are used to calculate a spa tial distribution map of laser pulses. The optimal values of the param eters are determined with a computer model, for a system that produces 213-nm radiation with a Gaussian beam-intensity distribution and a pe ak radiant exposure of 400 mJ/cm(2). The model shows that with a beam diameter of 0.5 mm, an overlap of 80%, and a 5-mm treatment zone, the roughness is less than 6% of the central ablation depth, the refractiv e error after correction is less than 0.1D for corrections of myopia o f 1, 3, and 6 D and less than 0.4 D for a correction of myopia of 10 D , and the number of pulses per diopter of correction is 2500 when the beam-intensity distribution is Gaussian and 580 when it is flat.