Comparison of Combination Posterior Sub-Tenon Triamcinolone and Modified Grid Laser Treatment with Intravitreal Triamcinolone Treatment in Patients with Diffuse Diabetic Macular Edema

PURPOSE: To compare the efficacy of posterior sub-Tenon's capsule triamcinolone acetonide injection combined with modified grid macular photocoagulation (PSTI + MP) with intravitreal triamcinolone acetonide (IVTA) injection in the treatment of diffuse diabetic macular edema (DME). MATERIALS AND METHODS: Forty eyes of 33 patients with diffuse DME were randomly allocated into either PSTI + MP (20 eyes) or IVTA (20 eyes). Best corrected visual acuity (VA) and foveal thickness were measured. RESULTS: The ETDRS scores at baseline were 25.2 ± 13.6 (mean ± SD) letters in the PSTI + MP group, whereas 21.7 ± 16.3 letters in the IVTA group. The ETDRS scores improved by 33.2 ± 15.9, 34.7 ± 16.6 and 30.9 ± 19.0 letters in the PSTI + MP group whereas by 30.9 ± 15.4, 30.1 ± 17.9 and 31.5 ± 15.0 letters in the IVTA group at 1, 3, and 6 months after the treatments, respectively. The VA improved significantly at 1 month and 3 months after both treatments (all p < 0.02, paired t-test). The VA improvements were no longer significant at 6 months in either group. There were no statistically significant differences at any time points between the 2 groups (all p > 0.05, Student's t-test). The foveal thicknesses at baseline and 1, 3, and 6 months after the treatments were 382.8 ± 148.3, 309.1 ± 131.3, 319.3 ± 93.3, 340.4 ± 123.5 µm (mean ± SD) in the PSTI + MP group vs. 369.1 ± 123.1, 241.4 ± 52.3, 277.5 ± 137.4, 290.2 ± 127.9 µm in the IVTA group, respectively. Pairwise comparisons revealed significant decrease in foveal thickness at 1 month (p = 0.01, paired t-test) for the PSTI + MP group, and at both 1 month (p < 0.001) and 3 months (p = 0.016) for the IVTA group. There were no statistically significant differences at any time points between the 2 groups (all p > 0.05, Student's t-test). In contrast to the PSTI + MP group, where no complications were noted, the elevation of intra-ocular pressure in 3 of 20 eyes (15%) and a significant increase in average cataract grading were observed in the IVTA group. CONCLUSION: PSTI + MP treatment provides significant improvement of vision in patients with diffuse DME over 3 months, and achieves outcomes comparable to those after IVTA treatment, however, with fewer complications.