Collagen cross-linking with administration of riboflavin and UV radiation may delay or halt the progression of keratoconus. This study examines the effects of the treatment on the corneal wavefront error.Twenty eyes of 20 patients with keratoconus received collagen cross-linking with riboflavin administration and 30 min of UV radiation at a wavelength of 365 nm. Preoperatively as well as 1 and 6 months postoperatively, the corneal wavefront error was computed from axial keratometric topography data by Zernike decomposition over a pupil diameter of 6 mm.Preoperative mean keratometric astigmatism was 5.37 +/- 2.36 D. Six months postoperatively it was 5.29 +/- 2.73 D (p = 0.35). Total higher order aberrations were preoperatively 3.35 +/- 1.65 microm and after 6 months 3.31 +/- 1.79 microm (p = 0.116). Coma's root mean square was 2.94 +/- 1.47 microm preoperatively and 2.75 +/- 1.38 microm after 6 months (p = 0.047).Within the first 6 postoperative months, collagen cross-linking with riboflavin administration and UVA irradiation does not significantly increase or decrease corneal wavefront aberrations.