AIM:To compare the changes of macular microcirculation in eyes with idiopathic and diabetic macular epiretinal membrane(ERM)before and after pars plana vitrectomy(PPV), and to evaluate the prognosis of the two types of ERM.METHODS:We conducted a retrospective study on 24 patients(24 eyes), 12 patients(12 eyes)with idiopathic macular epiretinal membrane(iERM)and 12 patients(12 eyes)with diabetic macular epiretinal membrane(dERM)who underwent PPV combined with ERM and internal limiting membrane(ILM)peeling from April 2020 to July 2020. In addition, 16 contralateral healthy eyes of iERM patients who underwent PPV combined with ERM and ILM removal from September 2019 to July 2020 were selected as the normal control group. All patients were followed up for more than 3mo. The area of foveal avascular zone(FAZ)and the macular vascular density(MVD), including superficial macular vascular density(SVD)and deep macular vascular density(DVD)were compared before and after surgery. And the prognosis was also analysed.RESULTS: The area of FAZ in the iERM group and dERM group before surgery were significantly smaller than that in the control group(P<0.05); The total SVD in the iERM and dERM groups were lower than that in the control group, and the dERM group was lower than that in the iERM group, but no statistically significant difference was found. The total DVD in the iERM and dERM groups was significantly lower than that in the control group(P<0.05). The foveal SVD in the iERM was significantly higher than that in the dERM and control groups, and the foveal DVD in the iERM was significantly higher than that in the control group(P<0.05). The parafoveal SVD in the iERM and dERM groups were lower than that in the control group, but only the difference was obvious between the dERM and the control group(P<0.05). The parafoveal DVD in the iERM and dERM groups were significantly lower than that in the control group(P<0.05). Postoperative visual acuity was significantly improved in the iERM group and dERM group(P<0.05), but the SVD was barely changed. The total and parafoveal DVD in the iERM group were statistically higher than those before surgery(P<0.05). DVD in the dERM group was higher than it was before surgery, but with no statistically difference. There were no differences in the visual acuity, SVD and DVD between the iERM and dERM groups after operation.CONCLUSION: The changes of macular microcirculation in dERM were more obvious than those in iERM. DVD in the iERM patients was improved at the early stage after operation, while the improvement was not obvious in the dERM patients.