METHODS: A total of 30 eyes in 19 patients with diabetic macular edema(DME), who were diagnosed through fundus fluorescein angiography, consecutively recruited from March 2010 to March 2014 and were treated with macular grid pattern photocoagulation. Multifocal electroretinogram(mfERG)system(version 3.15)was performed before and after photocoagulation therapy for 3mo. All data were statistically analyzed.

RESULTS: The amplitude densities of a-ware and b-ware for the fovea increased after macular grid pattern photocoagulation therapy, and there were significantly changes relative to its preoperation(t=-3.7683, P<0.01; t=-3.6570, P<0.01). No remarkable changes in the latency of a-ware and b-ware of fovea were measured before and after photocoagulation(t=1.7103, P>0.05; t=1.5623, P>0.05 ). Compared with pretreatment, the amplitude densities of a-ware and b-ware at macular were statistically larger(t=4.8337, P<0.01; t=-2.0376, P<0.05). The latency of a-wave and b-wave at macular was significant longer after treatment(t=-2.1892, P<0.05; t=-3.5024, P<0.01). There were no significant differences in the amplitude densities of a-ware and b-ware at paramacular after therapy(t=-1.4387, P>0.05; t=-0.1766, P>0.05). It was significant longer in the latency of a-wave and b-wave at paramacular after photocoagulation(t=-2.0905, P<0.05; t=-2.5646, P<0.05).

CONCLUSION: The laser photocoagulation treatment for DME can improve the retinal function at fovea, which benefits the vision acuity. Unfortunately,it induces extensively damaging effects on the macula and paramacular.