Comparison of Intravitreal versus Posterior Sub–Tenon’s Capsule Injection of Triamcinolone Acetonide for Diffuse Diabetic Macular Edema

Abstract

To compare the safety and efficacy of intravitreal versus posterior Sub-Tenon's capsule injection of triamcinolone acetonide for diffuse diabetic macular edema. Prospective, double-masked, randomized controlled trial. Twelve patients (24 eyes) with bilateral diffuse diabetic macular edema. One eye of each patient was randomly assigned to receive a single 4-mg triamcinolone acetonide intravitreal injection and the fellow eye to receive a 40-mg triamcinolone acetonide posterior Sub-Tenon's capsule injection. Changes in visual acuity and central macular thickness obtained using optical coherence tomography were measured during a 6-month follow-up. Potential treatment complications were monitored, including increases in intraocular pressure (IOP) and cataract progression. Both intravitreal and Sub-Tenon's capsule injections of triamcinolone acetonide resulted in significant but transient improvements in central macular thickness. The mean (+/-standard deviation [SD]) central macular thickness in eyes with intravitreal injection was significantly thinner than in the Sub-Tenon's capsule-injected eyes at 1 month (226.8+/-41.7 microm and 431.5+/-165.8 microm, respectively; P = 0.002) and 3 months (242.3 +/- 93.9 microm and 364.7+/-78.2 microm, respectively; P = 0.005) after triamcinolone acetonide injection. The mean visual acuity (logarithm of the minimum angle of resolution) in the intravitreally injected eyes was significantly better than in the Sub-Tenon's capsule-injected eyes at 3 months post injection (0.832+/-0.293 and 1.107+/-0.339, respectively; P = 0.004). Intraocular pressure did not show any significant difference between the 2 forms of triamcinolone acetonide delivery at any follow-up visit, and no eyes had IOPs >25 mmHg. The findings from our study neither advocate nor support the use of corticosteroids for the treatment of diabetic macular edema, but do imply that both intravitreal and Sub-Tenon's capsule injections of triamcinolone acetonide may be equally tolerated, with short-term performance clearly favoring the intravitreal (4 mg) more than the SBT capsule (40 mg) route for the anatomic and functional aspects of improvement tested in this investigation.