PURPOSE. To evaluate relationships among contrast sensitivity function, ocular higher-order aberration, and myopic correction in eyes undergoing overnight orthokeratology for myopia. METHODS. A prospective study was conducted in 46 eyes of 23 patients undergoing orthokeratology. Inclusion criteria were spherical equivalent refraction between –1.00 and –4.00 diopters (D), refractive astigmatism up to 1.00 D, and best-corrected visual acuity of 20/20 or better. Ocular higher-order aberrations and contrast sensitivity function were determined before and 3 months after initiation of the procedure. We measured three indices of contrast sensitivity function: contrast sensitivity, low-contrast visual acuity, and letter contrast sensitivity with the CSV-1000 charts (Vector Vision Co., Greenville, OH). Area under the log contrast sensitivity function (AULCSF) was calculated from the contrast sensitivity data. RESULTS. Orthokeratology significantly improved logMAR uncorrected visual acuity (P � 0.0001; paired t-test) but significantly increased ocular higher-order aberrations (P � 0.0001) and decreased contrast sensitivity function, including AULCSF (P � 0.0001), low-contrast visual acuity (P � 0.0025), and letter contrast sensitivity (P � 0.0001; Wilcoxon signed-rank test). The induced changes in AULCSF, low-contrast visual acuity, and letter contrast sensitivity by orthokeratology showed significant correlation with changes in third-order (Pearson r � –0.430, P � 0.0026; r � 0.423, P � 0.0031; and Spearman rs � –0.351, P � 0.0186, respectively), fourth-orde
