Macular microvasculature features before and after vitrectomy in idiopathic macular epiretinal membrane: an OCT angiography analysis

To evaluate pre-operative and post-operative morphologic characteristics in idiopathic macular epiretinal membrane (ERM) by optical coherence tomography angiography (OCTA). Thirty-three subjects with unilateral idiopathic ERM were enrolled and the contralateral eyes served as controls. Vascular parameters including superficial capillary plexus (SCP), deep capillary plexus (DCP), outer capillary plexus (OCP), and choroidal capillary plexus (CCP) were evaluated by OCTA. The superficial foveal avascular zone (FAZ) was significantly smaller in eyes with ERM (P < 0.0001). The vessel densities (VDs) were significantly increased in the fovea but dramatically decreased in the parafovea in SCP and DCP of ERM eyes (all P < 0.0001), in contrast to those in OCP and CCP. The blood flow was augmented in OCP but declined in choroid compared with the controls. In CCP, the mean foveal VD in ERM was significantly smaller (P = 0.023), whereas parafoveal VD did not significantly change (P = 0.66). At 6 months after surgery, flow area was decreased in OCP (P = 0.0007), and foveal and parafoveal VDs were significantly altered in all layers except the foveal VD in OCP and the choroid (all P < 0.05). The total and inner retinal thickness of the fovea and parafovea were correlated with pre-operative and post-operative visual outcomes, respectively. Smaller FAZ and greater interocular differences between post-operative and fellow eyes in FAZ were associated with worse post-operative visual outcomes. OCTA provides a better display of the vascular network of the retina and choroid to evaluate the severity and surgical prognosis of ERM patients.