Computer-assisted analysis of corneal topography, using an EyeSys Corneal Analysis System instrument, was performed on 20 normally sighted human eyes that underwent excimer laser photorefractive keratectomy (PRK) to correct high myopia from 6.00 to 17.00 D (mean 10.90 +/- .SD 2.90 D). Ablations utilized one or two zones, at a single time, with an ExciMed UV200 193-nanometer excimer laser (Summit Technology, Inc, Waltham, Mass). Mean follow up was 28.9 weeks (+/- 13). Decentered treatment caused an average error of 1.06 D in the attempted refractive result.