- Macular edema is the main cause of visual impairment in diabetic patients. Its treatment is mainly based on laser photocoagulation. Intravitreal triamcinolone acetonide (TA) has recently been proposed as a new treatment for eyes with diabetic macular edema resistant to conventional laser photocoagulation. To evaluate the one year efficacy and safety of a single TA injection administered for diffuse diabetic macular edema unresponsive to prior laser treatment. Interventional case series. Setup: University medical center out-patient clinic. Twenty-one patients with bilateral diffuse diabetic macular edema. A single intravitreal injection of triamcinolone acetonide. Visual acuity measured by ETDRS score, retinal area evaluation clinically and retinal thickness evaluation by Retinal Thickness Analysis (RTA) at 3 and 12 months following injection. Secondary outcomes were intraocular pressure control and cataract progression. Results: Three months following injection, the mean improvement in visual acuity was 4.7 +/- 11.7 letters in the study group as compared to 0.2 +/- 11.4 in the control group (p = 0.18). No difference was noticed one year following injection. Clinical assessment of the retinal area of edema revealed a substantial difference between patients and controls at 3 months (p = 0.0006) and at one year (p = 0.05). RTA evaluation revealed improvement in retinal thickness solely at the 3 months exam. Four eyes developed high intraocular pressure and required treatment (p = 0.054). No difference in cataract progression was noted between the two groups (p = 0.69). Injection of TA may improve visual acuity for a limited time. Increased intraocular pressure is a frequent side effect. During a one year follow-up, no evidence of ocular toxicity was noted in eyes with diffuse diabetic macular edema.