The effect of ketorolac tromethamine 0.5% ophthalmic solution (a new nonsteroidal anti-inflammatory agent) treatment was compared to placebo treatment in patients with chronic, angiographically proven aphakic or pseudophakic cystoid macular edema (visual acuity less than or equal to 20/40 for six months) during a three- to four-month double-masked, randomized study. Twenty-six patients completed this study without significant ocular or systemic toxicity. The improved distance visual acuity observed in the ketorolac treatment group (8/13 patients) was statistically different from the improved vision observed in the placebo treated group (1/13 patients) (P = .005). No patient on a regimen of ketorolac therapy had a significant decrease in Snellen distance visual acuity while on treatment, but two patients in the placebo group demonstrated a decrease in visual acuity of two lines or more. Fluorescein angiography was consistent with changes in visual acuity.