Comparison of intravitreal versus posterior sub-tenon's capsule injection of triamcinolone acetonide for diffuse diabetic macular edema

Purpose: To compare the safety and efficacy of intravitreal versus posterior sub-Tenon's capsule injection of triamcinolone acetonide for diffuse diabetic macular edema. Design: Prospective, double-masked, randomized controlled trial. Participants: Twelve patients (24 eyes) with bilateral diffuse diabetic macular edema. Intervention: 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 acetonicle posterior sub-Tenon's capsule injection. Main Outcome Measures: 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. Results: Both intravitreal and sub-Tenon's capsule injections of triamcinolone acetonicle 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 mu m and 431.5 +/- 165.8 mu m, respectively; P = 0.002) and 3 months (242.3 +/- 93.9 mu m and 364.7 +/- 78.2 mu m, respectively; P = 0.005) after triamcinolone acetonicle 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. Conclusions: 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.