Association of OCT angiography and multifocal electroretinography findings with early anatomical response to intravitreal bevacizumab in diabetic macular oedema

Purpose: To characterise systemic, microvascular and retinal functional features in treatment-naive centre-involving diabetic macular oedema (DME) using optical coherence tomography angiography (OCTA) and multifocal electroretinography (mfERG), and to explore their association with early anatomical response after three monthly intravitreal bevacizumab injections. Methods: In this prospective study, 73 eyes of 73 participants (30 treatment-naive centre-involving DME, 20 diabetes mellitus without diabetic retinopathy (DR), 23 healthy controls) underwent macular OCTA and standardised mfERG at baseline. DME eyes received three monthly bevacizumab injections with repeat OCTA. Anatomical response was defined by central subfield thickness (CST) reduction and functional response by ≥1 Snellen-line gain in best-corrected visual acuity (BCVA). Results: Anatomical non-responders had higher HbA1c and higher baseline parafoveal vessel density (VD) in the deep capillary plexus (DCP) and inner retinal slab (IR slab). After adjustment for HbA1c, baseline BCVA and CST, higher parafoveal IR slab VD remained associated with a smaller percentage CST reduction (B = −1.55; 95% CI, −2.88 to −0.22; p = 0.024), whereas DCP VD did not. Responders showed higher central (0–2°) P1 amplitude and root mean square responses. A higher 0–2° P1/N1 ratio characterised functional responders. Cross-sectionally, DME showed lower VD and choriocapillaris flow; diabetic eyes without DR had preserved OCTA metrics despite mfERG abnormalities. Conclusions: Early anatomical response to bevacizumab in DME was associated with distinct baseline systemic, microvascular and electrophysiological patterns. These exploratory findings require validation in larger independent cohorts and with other anti-vascular endothelial growth factor agents before clinical predictive value can be established.