PURPOSE: The effectiveness of intravitreal triamcinolone acetonide in the treatment of cystoid macular edema from central retinal vein occlusion (CRVO) was investigated. DESIGN: A noncomparative, prospective, interventional case series. METHODS: In a clinical practice, 18 patients were enrolled with nonischemic CRVO and cystoid macular edema. Two milligrams of triamcinolone acetonide were injected into the vitreous of only one eye from each patient. The outcome measures were 1-mm mean central retinal thickness on optical coherence tomography and visual acuity. RESULTS: Mean duration of symptoms before surgery was 2 months (SD, 1.3 months). Ten patients required repeated injections for recurrent cystoidmacular edema (mean,1.8 injections). Mean visual acuity significantly improved from 20/300 to 20/166 (P=.007) at 1 month, 20/100 (P=.0005) at 2 months, 20/130 (P=.007) at 3 months, and 20/150 (P=.02) at 6 months but deteriorated again to 20/270 (not significant) at 12 months. There was a significant improvement in retinal thickness from presentation 518 μm, to 363 μm (P=.03) at 1 month, 304 μm (P=.04) at 2 months, and 353 μm (P=.01) at 3 months but not from presentation at 6 months (mean, 383 μm) and 12 months (mean, 406 μm). Eleven patients suffered intraocular pressure rises requiring intervention. Intravitreal triamcinolone acetonide did not prevent collateral circulation formation, which was seen in 10 patients. CONCLUSION: Intravitreal corticosteroid injection is very effective in reversing cystoid macular edema and improving visual acuity in recent-onset nonischemic CRVO in the first 6 months, but this is unfortunately not sustained at 1 year. METHODS: In a clinical practice, 18 patients were enrolled with nonischemic CRVO and cystoid macular edema. Two milligrams of triamcinolone acetonide were injected into the vitreous of only one eye from each patient. The outcome measures were 1-mm mean central retinal thickness on optical coherence tomography and visual acuity. RESULTS: Mean duration of symptoms before surgery was 2 months (SD, 1.3 months). Ten patients required repeated injections for recurrent cystoid macular edema (mean, 1.8 injections). Mean visual acuity significantly improved from 20/300 to 20/166 (P = .007) at 1 month, 20/100 (P = .0005) at 2 months, 20/130 (P = .007) at 3 months, and 20/150 (P = .02) at 6 months but deteriorated again to 20/270 (not significant) at 12 months. There was a significant improvement in retinal thickness from presentation 518 μm, to 363 μm (P = .03) at 1 month, 304 μm (P = .04) at 2 months, and 353 μm (P = .01) at 3 months but not from Intravitreal triamcinolone acetonide did not prevent collateral circulation, which was seen in 10 patients. CONCLUSION: Intravitreal corticosteroid (mean, 383 μm) and 12 months (mean, 406 μm) injection is very effective in reversing cystoid macular edema and improving visual acuity in recent-onset non-chemical CRVO in the first 6 months, but this is unfortunately not sustained at 1 year.