Objective To investigate the impact of cystoid macular edema (CME) on visual acuity in patients with uveitis. Design Cross-sectional study. Participants The data from 529 patients (842 eyes) with uveitis were analyzed. Main Outcome Measures We recorded gender and age of the patients, anatomic site and diagnosis of uveitis, associations with systemic diseases, onset and duration of uveitis, presence of CME, best-corrected visual acuity, and the causes of decrease in visual acuity. Results Cystoid macular edema was noted in 175 (33%) of all uveitis patients, of whom 77 (44%) had visual acuity of 20/60 or less in at least 1 eye. The mean visual acuity for eyes with CME was significantly worse than for eyes without CME (0.25 vs. 0.4; P = 0.003). Of all uveitis patients, 185 (35%) had visual acuity of 20/60 or less in at least 1 eye, which was caused by CME in 77 (42%) patients. Poor visual acuity in patients with CME was associated with the advanced age of the patients, chronic inflammation, and various specific uveitis entities. The development of visually impaired or blind eyes in patients with panuveitis and intermediate uveitis was caused in most cases by CME (59% and 85%, respectively). Conclusions Cystoid macular edema was a major cause of visual loss in patients with uveitis. The unsatisfactory visual acuity in patients with uveitis underlines the need for improved management of this complication.