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Comparision of multifocal electroretinogram and optical coherence tomography in diabetic retinopathy before and after photocoagulation

Objective　Toinvestigate the influence of photocoagulation on macular function and morphous in patients with diabetic retinopathy (DR).Methods　Forty eyes of thirty patients with severe nonproliferative diabetic retinopathy (NPDR) were examined by multifocal electroretinogram (mfERG) and optical coherence tomography (OCT) before and 2,7, and 14 days after photocoagulation. The results were statistically analyzed by using analysis of variance and t test; the changes of macular function and macular fovea thickness were detected and observed.Results　P1 response densities of ring 1,3,and 5 were 131.79plusmn;50.92，37.50plusmn;17.27，24.07plusmn;11.49，respectively,2 days after photocoagulation; and were 212.96plusmn;53.75，46.70plusmn;15.89，and 30.91plusmn;10.78, respectively, before photocoagulation. The densities before and after photocoagulation differed much（t=7.910, 2.174, 2.205; Plt;0.05）. N1 response density of ring 4 was（60.39plusmn;20.69） and the prephotocoagulation corresponding response density was （107.11plusmn;44.63）; the difference was significant（t=5.375，Plt;0.01）. The latency of P1 of ring 4 was（41.83plusmn;3.41），which had significant statistically difference（t=-2.770，Plt;0.05) with that before photocoagulation（39.52plusmn;2.64); there was no significant changes in the latency of N1 (Pgt;0.05). The most significant changes of P1 and N1 response densities occurred in the central macular 5deg; area. Seven days after photocoagulation, the response density of P1 and N1 in the central macular 5deg; area seemed to be recoverd to some extend and increased to （179.70plusmn;47.10）and (81.11plusmn;34.18) respectively until 14 days after photocoagulation, which was still much lower than that before the photocoagulation（t=3.840, 2.746; P＜0.05）; the response densities of other areas had no significant differences (P＞0.05). Seven days after photocoagulation,the latency of P1 in ring 4 was delayed to（41.78plusmn;3.57）, which had significant difference（t=-3.144，P＜0.01）with that before the photocoagulation（39.52plusmn;2.64) ; but there was no significant difference between 14 days after photocoagulation and prephotocoagulation (t=-1.809，P＞0.05). The latency of N1 in ring 1 was（20.67plusmn;3.85）at seven days after photocoagulation, It had no significant difference (t=-1.171,P＞0.05) with that before the phtocoaguation（18.78plusmn;3.29）. Before and 2 days after photocoagulation, the macular fovea thickness were（224.42plusmn;122.88）and（274.85plusmn;108.20）respectively, and the difference was statistically significant（t=-2.420，P＜0.05）. Forteen days after photocoagulation，the macular fovea thickness was（236.29plusmn;70.45），It had no significant difference with that before the photocoagulation（t=-0.578，P＞0.05）. Before and seven days after photocoagulation, P1 response density had obvious negative correlation with corresponding macular fovea thickness（r=-0.755，Plt;0.01; r=-0.594，Plt;0.05）. Conclusions 　After photocoagulation in patients with DR，the macular function decreased in a certain degree，and the relationship of macular retinal function and macular morphology changes was close; combination of mfERG and OCT can evaluate macular function and macular morphology structure comprehensively and objectively.