PURPOSE: To evaluate the refractive results and safety of PRK (photorefractive keratectomy) based on the preoperative corneal topography. METHODS: 44 operated eyes, using the photorefractive keratectomy process, and which presented preoperative topographical abnormalities. The control group consisted of 44 eyes with preoperative normal corneal topography. Eighty-eight eyes were submitted to the photorefractive keratectomy process using the Summit Apex plus Excimer Laser. Corneal topographies were accessed by the EyeSys Analysis system; the topographic abnormalities which were considered are the following: apex displacement above 1.5D (AD), asphericity above 0.25D/mm (AS), obliquity above 15 degrees (OB), inferior-superior asymmetry equal to or more than 1.5D (IS), curvature above 47D (CU) and two combined features (CB). Main measured outcome: loss of one or more lines were safety defined for the prognosis. RESULTS: All patients were followed up during 6 months. A significant loss of BCVA occurred in PRK-AD (p<0.001) and PRK-CO (p<0.05). CONCLUSION: These data suggest that patients, who wish to be submitted to the refractive surgery must undergo preoperative corneal topography analysis and if any topographic abnormality is found in these patients, this can indicate the loss of lines of corrected vision after surgery.
Myopia; Laser surgery; Keratectomy; photorefractive; Excimer laser; Cornea topography; Refractive errors; Low vision
