Purpose: To evaluate refractive outcomes of custom laser in situ keratomileusis (LASIK) based on undilated and pharmacologically dilated wavefront aberrometry with the Visx laser system. Setting: Clinical refractive practice, St. Louis, Missouri, USA. Design: Comparative case series. Methods: Eyes that had LASIK using dilated wavescans (study group) were evaluated for the reason for use of dilated scans; age; preoperative refractive error; preoperative root mean square (RMS), coma, trefoil, and spherical aberration values; postoperative uncorrected distance visual acuity (UDVA); postoperative refractive error; percentage of iris-registration capture; and enhancement rate. The study group was compared with a control group that had LASIK using undilated wavescans. Results: The study group comprised 52 eyes (31 patients) and the control group, 104 eyes (55 patients). At 1 month, the mean postoperative UDVA was 20/21 in the study group and 20/22 in the control group and at 3 months, 20/22 and 20/20, respectively. At 1 month, the mean postoperative spherical equivalent (SE) was +0.07 diopter (D) ± 0.49 (SD) in the study group and +0.14 ± 0.30 D in the control group and at 3 months, -0.01 ± 0.44 D and +0.02 ± 0.23 D, respectively; there was no statistically significant difference between groups at either timepoint. There was no statistically significant difference in preoperative RMS or postoperative coma, trefoil, or spherical aberration between the groups. Although the study group had a slightly higher enhancement rate, the difference was not statistically significant. Conclusion: Compared with custom LASIK based on undilated wavescans, use of dilated wavescans for custom LASIK resulted in comparable postoperative outcomes. Financial Disclosure: No author has a financial or proprietary interest in any material or method mentioned.