Perfusion Density Changes After Epiretinal Membrane Surgery Predominantly Reflect Topographic Redistribution of Macular Vasculature

PURPOSE: To evaluate changes in optical coherence tomography angiography (OCTA) flow parameters and its clinical aspects in idiopathic epiretinal membrane (iERM). METHODS: Thirty-seven unilateral iERM patients who were followed up at least 6 months after iERM surgery were retrospectively reviewed. All eyes were imaged using a 6x6 mm volume scan of the swept source OCTA. The best corrected visual acuity, the foveal avascular zone (FAZ) area, perfusion density (PD) within 1-, 3-mm circle (PD1 and PD3), and the distance between the fovea and vascular arcades (FV) were assessed. RESULTS: The FAZ areas increased and PD1s decreased in the superficial and deep capillary plexus (SCP and DCP) (P < 0.05 in all). In SCP, the FAZ area showed an inverse correlation with PD1. The association was observed between changes in FV and PD1 in SCP and DCP (r =0.364, 0.412, p =0.044, 0.021). The changes in the PD3s were not correlated with the changes in FV. The change in BCVA was significantly correlated with the changes in FAZ area (r = -0.514, p < 0.05), PD1 (r = 0.325, p < 0.05), and PD3 (r = 0.424, p < 0.05). CONCLUSIONS: In iERM, greater FAZ enlargement correlated with greater visual improvement despite a reduction in central PD. The significant relationship between changes in FV and PD suggests that changes in OCTA flow parameters after iERM surgery predominantly reflect topographic redistribution of macular vasculature rather than a true loss of perfusion, although a concurrent perfusion change cannot be entirely excluded.