AIM:To retrospectively analyze the therapeutic effects of "C" and ring grid photocoagulation in the treatment of diabetic macular edema(DME).METHODS:A total of 97 eyes with diffuse diabetic macular edema were involved in the present study.All eyes were treated with grid photocoagulation:60 eyes received "C" grid photocoagulation and 37 eyes received ring grid photocoagulation.The visual acuity and the macular edema were followed up for 6 months.RESULTS:After treatment with "C" grid photocoagulation,diabetic macular edema completely disappeared in 14 eyes(23%),partly disappeared in 38 eyes(63%),and remained unchanged in 8 eyes(13%).After treatment with ring grid photocoagulation,diabetic macular edema completely disappeared in 7 eyes(19%),partly disappeared in 26 eyes(70%),and remained unchanged in 4 eyes(11%),which was not significantly different from "C" grid photocoagulation(P=0.852).After treatment with "C" grid photocoagulation,visual acuity(VA) was improved in 13 eyes(22%),maintained unchanged in 41 eyes(68%),and decreased in 6 eyes(10%).After treatment with ring grid photocoagulation,VA was improved in 6 eyes(16%),maintained unchanged in 27 eyes(73%),and decreased in 4 eyes(11%),which was not significantly different from "C" grid photocoagulation(P=0.570).CONCLUSION:There is not significant difference between "C" and ring grid photocoagulation in the treatment of DME."C" grid photocoagulation is appropriate for most DME.But ring grid photocoagulation is necessary if there is edema in macular-disc fiber.