Toshiyuki Oshitari, Sakiko Nonomura, Miyuki Arai, Yoko Takatsuna, Eiju Sato, Takayuki Baba, Shuichi Yamamoto Department of Ophthalmology and Visual Science, Graduate School of Medicine, Chiba University, Chuo-ku, Chiba, Japan Purpose: To compare the effects of sub-Tenon's capsule triamcinolone acetonide (STTA) injection to that of STTA injection combined with microaneurysm photocoagulation (MAPC; STTA + MAPC) on eyes with diabetic macular edema (DME). Patients and methods: The medical records of 138 eyes of 138 patients with DME treated by either STTA or STTA + MAPC were reviewed. The degree of DME was determined by the optical coherence tomographic features: patients with serous retinal detachment (SRD+; 38 eyes) and patients without SRD (non-SRD; 100 eyes). The central macular thickness (CMT) and the best-corrected visual acuity (BCVA) were measured periodically for 6 months after the treatments. Results: The BCVA was significantly improved in the non-SRD group after STTA + MAPC. The CMT was significantly improved in all groups and improved considerably more in the non-SRD group than in the SRD+ group after STTA + MAPC. Conclusion: Our findings indicate that MAPC has an additive effect in the non-SRD type. Keywords: diabetic macular edema, sub-Tenon's triamcinolone acetonide injection, microaneurysm photocoagulation, best-corrected visual acuity, central macular thickness