Effects of Decentration of Photorefractive Keratectomy on the Induction of Higher Order Wavefront Aberrations

PURPOSE: To evaluate the effects of ablation decentration on the induction of higher order wavefront aberrations (HOAs) in active eye-tracker-assisted myopic photorefractive keratectomy (PRK) using the VISX STAR S4 laser with ActiveTrak (Abbott Medical Optics [AMO]). METHODS: Ninety-four myopic eyes (53 patients) were divided into three groups according to ablation decentration (group 1, <= 0.15 mm, 20 eyes; group 2, >0.15 to <= 0.30 mm, 54 eyes; and group 3, >0.30 mm, 20 eyes). The distances of ablation centers from the centers of the entrance pupils were analyzed using corneal topography. Wavefront errors were measured preoperatively and at 6 months after PRK using a VISX WaveScan aberrometer (AMO). Statistical analysis was performed to assess the influence of ablation decentration on PRK-induced HOAs. RESULTS: The mean decentration was 0.23 +/- 0.10 mm (range: 0.04 to 0.52 mm). The magnitude of all HOAs was significantly increased at 6 months postoperatively (P<.05). Increases in PRK-induced HOAs including total HOA, coma, and spherical aberration were significantly different among the three groups (P<.05). Statistically significant differences were noted between pairs of data in group 1 versus group 3 for total HOA (P=.015), coma (P=.038), and spherical aberration (P=.038), and group 2 versus group 3 for coma (P=.049). CONCLUSIONS: Ablation decentration >0.30 mm from the center of the entrance pupil was associated with greater induction of total HOA, coma, and spherical aberration after PRK, as compared with ablation decentration <0.15 mm. In addition, ablation decentration has a more significant influence on coma-inducing effects. [J Refract Surg. 2010;26(10):731-743.] doi:10.3928/1081597X-20091209-01