Because the course of ocular inflammatory disease can be variable, a double-masked, randomized, crossover trial was designed to test the efficacy of acetazolamide compared with a placebo for the treatment of uveitis-associated cystoid macular edema. Randomized adult patients received either oral acetazolamide sodium 500 mg or a matched placebo every 12 hours for the first 4 weeks of the study. Children 8 years of age or older received a lesser dose based on body weight. Following a 4-week period, during which no medication was given, patients then received a 4-week course of the opposite medication. Primary end points included reduction in cystoid macular edema (graded on fluorescein angiography) and improvement in visual acuity (measured on standardized Early Treatment Diabetic Retinopathy Study [ETDRS] charts). Laser acuity was also assessed as a secondary outcome variable. Adverse effects of the acetazolamide therapy were monitored by clinical and laboratory examinations.