Topographical evaluation of centration of excimer laser myopic photorefractive keratectomy

We evaluated the centration of excimer laser myopic photorefractive keratectomy by analyzing the corneal topography in 60 eyes of 37 patients. Computer-assisted analysis of corneal topography was performed preoperatively and one week postoperatively. The distance and the direction from the center of the entrance pupil to the center of the ablation was calculated using a personal computer. Downward displacement of the ablation relative to the center of the entrance pupil was observed in 51 eyes (85%). The mean distance of the center of the ablation from the center of the entrance pupil was 0.51 +/- 0.31 mm (range 0.06 mm to 1.64 mm). To achieve more precise centration, we recommend applying an eye-movement tracking system to photorefractive keratectomy.