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 photorefractivekeratectomy (PRK) using a new algorithmic correction for the NidekEC-5000 excimer laser. A modified algorithm was obtained from themanufacturer after data previously presented indicated that the existingalgorithm tended to overcorrect the spherical error and undercorrect theastigmatism. In the new algorithm the spherical component wasundercorrected as the associated cylinder increased and the cylinder wasovertreated by a similar amount. In this study, 482 consecutive patientsundergoing PRK & photoastigmatic refractive keratectomy were evaluated.The spherical corrections performed were between 0.00 D and 10.75 D andthe astigmatic corrections between -0.00 D and -3.50 D. Postoperativeresults 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 Dand mean astigmatism of -0.45 D +/- 0.40 D. Vector analysis showed thatmean surgically induced astigmatism was +0.29 D +/- 1.02 D. Whencompared with results obtained using the original algorithm thesepatients achieved improved spherical corrections although theirastigmatic results were similar. It is recommended that manufacturer'salgorithms are regularly updated on the basis of the actual patientresults.