Purpose: To assess the crystalline lens opacity level by measuring ocular light scattering with a double-pass system. Design: Prospective, single-center, cross-sectional study. Methods: Two hundred fifty-three eyes of 135 patients referred for cataract evaluation were enrolled. Patients with corneal or retinal anomalies potentially impairing ocular transparency were excluded. Lens opacification was assessed by the Lens opacities classification system III. Optical Quality Analysis System (Visiometrics SL) measurements provided ocular Modulation Transfer Function cutoff frequency and Objective Scatter Index. Best-corrected visual acuity and Quality of Vision questionnaire scores (Rasch-scaled) were recorded. We analyzed correlations between visual acuity, type and severity of cataract, Optical Quality Analysis System measurements, and discomfort level in each group. Results: In patients with best-corrected visual acuity better than 20/32, we found correlations between Objective Scatter Index, Modulation Transfer Function, and visual acuity (r = 0.4, P <.0001). The Objective Scatter Index, Modulation Transfer Function, and visual acuity were correlated with each type of cataract. In patients with good visual acuity and moderate functional symptoms, the Objective Scatter Index values also were correlated to the severity of posterior subcapsular cataract (r = 0.4, P =.0006). Conclusions: Patients with incipient cataract may report visual discomfort, despite minor lens opacity on slit-lamp examination, minor loss of best-corrected visual acuity, or both. The measurement of ocular scattering with the Optical Quality Analysis System device may be a useful tool in the preoperative evaluation of patients with early cataract.