Natural history of corneal topography after excimer laser photorefractive keratectomy

PURPOSE: To investigate the natural history of corneal topography after excimer laser photorefractive keratectomy (PRK). DESIGN: A prospective, single center clinical study. PARTICIPANTS: A total of 40 eyes of 34 patients with myopia were studied. INTERVENTION: Excimer laser photorefractive keratectomy and computer-assisted videokeratography were performed. MAIN OUTCOME MEASURES: Preoperative, 1 week, and 1, 2, and 3 months postoperative topography patterns were compared and changes assessed by averaging defined sectors of the ablation zone in individual maps to produce composite "average" topography maps. RESULTS: Corneal topography was generally not homogeneous at 1 week after PRK. By 3 months, there had been considerable smoothing of corneal contour. A general "central island" effect early in the postoperative period flattened over time. When right and left eyes were evaluated independently, a tendency toward a keyhole-semicircular pattern was seen on average; the maximum flattening was nasal and the least flattening was inferotemporal for both right and left eyes. CONCLUSIONS: A tendency, on average, toward central island and keyhole-semicircular patterns is seen early in the postoperative course after PRK. Central islands tend to evolve into the keyhole-semicircular pattern, and the corneal topography in general after PRK tends to smooth considerably with time.