Refractive Results for the Nidek EC-5000 Excimer Laser Using a New Algorithmic Correction in 482 Eyes

Abstract

The goals of this study are to assess the results of photorefractive keratectomy (PRK) using a new algorithmic correction for the Nidek EC-5000 excimer laser. A modified algorithm was obtained from the manufacturer after data previously presented indicated that the existing algorithm tended to overcorrect the spherical error and undercorrect the astigmatism. In the new algorithm the spherical component was undercorrected as the associated cylinder increased and the cylinder was overtreated by a similar amount. In this study, 482 consecutive patients undergoing PRK & photoastigmatic refractive keratectomy were evaluated. The spherical corrections performed were between 0.00 D and — 10.75 D and the astigmatic corrections between −0.00 D and −3.50 D. Postoperative results at six months of follow-up showed a mean spherical equivalent of −0.05 ± 0.78 diopters, a mean spherical correction of +0.18 ± 0.77 D and mean astigmatism of −0.45 D ± 0.40 D. Vector analysis showed that mean surgically induced astigmatism was +0.29 D ± 1.02 D. When compared with results obtained using the original algorithm these patients achieved improved spherical corrections although their astigmatic results were similar. It is recommended that manufacturer’s algorithms are regularly updated on the basis of the actual patient results.