PURPOSE: To compare the postoperative outcomes of aspheric or prolate LASIK for myopia and myopic astigmatism. METHODS: In this double-blind, bilateral, randomized trial, 40 patients (80 eyes) with -0.75 to -7.00 diopters (D) of manifest refraction spherical equivalent (MRSE) underwent optimized aspheric treatment zone ablation (OATz group) in 1 eye and optimized prolate ablation (OPA group) in the fellow eye. Six-month postoperative outcomes were compared for MRSE and visual acuity, contrast sensitivity, patient satisfaction, ocular higher order aberrations (HOAs), and spherical aberration. The Wilcoxon signed rank test, Mann-Whitney U test, and paired t test were used for testing differences between groups. P<.05 was statistically significant. Main outcome measures included HOAs, spherical aberration, visual and refractive outcomes, and contrast sensitivity. RESULTS: Postoperatively, 36 patients (72 eyes) were evaluated. The MRSE was -0.07 +/- 0.23 D for the OPA group and +0.02 +/- 0.24 D for the OATz group (P>.05). Two (5%) eyes in the OPA group and 1 (3%) eye in the OATz group (P=.114) lost 1 line of corrected distance visual acuity. Postoperative visual acuity was not statistically different between groups (P>.05). Statistically lower change was noted in spherical aberration (0.011 mu m) in the OPA group versus the OATz group (0.099 mu m) (P<.001). Statistically higher induction of coma was noted in the OPA group (P=.035). No statistically significant differences were noted in photopic, mesopic, or glare contrast sensitivity and patient satisfaction between groups (P>.05, for all comparisons). CONCLUSIONS: The refractive and visual outcomes of OPA and OATz were equivalent. However, the postoperative optical quality of OPA-treated eyes was better. [J Refract Surg. 2012;28(2):112-119.] doi:10.3928/1081597X-20111219-01