Corneal Topography Six Years After Photorefractive Keratectomy for Myopia and Myopic Astigmatism
J Refract Surg. 2009 May;25(5):451-8.
To analyze the 6-year response of corneal topography to photorefractive keratectomy (PRK) for myopia and myopic astigmatism.
Twenty patients (40 eyes) who had PRK using the Technolas Keracor 217C excimer laser platform were followed up to 6 years after surgery. The eyes were subdivided into three groups according to the preoperative spherical equivalent refraction and astigmatism component. Corneal topographic maps were obtained with a Placido disk topographer (Keratron Scout). The pre- and postoperative topographical data were imported into custom software, which computed the average composite corneal map and average difference map for each study group to quantify the anterior corneal changes following laser ablation. The software defined three concentric zones of the surface topography, allowing characterization of the regional corneal response following surgery.
At 6 years, no changes in the surface topographic configuration of the central cornea were assessed following spherical myopic ablations in comparison with 1 year postoperatively. A slight peripheral flattening of approximately 0.60 diopters (D) (P < .001) was measured following the higher myopic ablations at 6 years compared with 1 year postoperatively. Minimal changes, of approximately 0.30 D (P < .001), in the anterior central cornea were observed following astigmatic correction during follow-up.
Photorefractive keratectomy for the correction of myopia provides stable comeal topography, with no clinically significant changes in the curvature profile at 6 years after surgery.