OBJECTIVES: To determine the effects of contact lens (CL) wear on biometry measurements for cataract surgery and whether a CL hiatus can reduce the prediction error of intraocular lens (IOL) calculations. METHODS: Retrospective, interventional case series of eyes that received repeat biometry measurements for IOL calculations after discontinuing hard or soft CLs for at least 14 days. PRIMARY OUTCOME MEASURES: intersession change in axial length, average keratometry, astigmatism, and axis. SECONDARY OUTCOME MEASURES: change in recommended IOL power and toricity, postoperative refraction prediction error. RESULTS: Thirty-two eyes of 16 patients had a mean duration of CL wear (12 hard and 20 soft) of 39.5 years (range, 29-55 years) and mean CL hiatus duration of 25 days (range, 14-56 days). Mean absolute intersession change in axial length was 0.016 mm (range, 0-0.05 mm), average keratometry 0.31 D (range, 0.02-1.01 D), astigmatism 0.41 D (range, 0.01-1.10 D), and axis 6.3° (range, 0-28°). The IOL power predicting the lowest postoperative spherical equivalent changed for 17 of 32 eyes (by 0.5 D for 12 eyes and 1.0 D for five eyes). Recommended IOL toricity changed for nine of 14 eyes (by 0.75 D for six eyes and 1.50 D for three eyes). The median absolute prediction error of IOL calculations was 0.69 D (range, 0.19-2.93 D) before and 0.57 D (range, 0.01-2.82 D) after the CL hiatus (P=0.16). CONCLUSIONS: Contact lens wear may affect biometry measurements and subsequent IOL power and toricity selection. For some eyes, repeating biometry measurements after a CL hiatus may improve the accuracy of IOL calculations.