En face OCT in branch retinal artery occlusion: quantitative assessment of epiretinal macrophage-like cells and optical intensity ratio

PURPOSE: In branch retinal artery occlusion (BRAO), the regional distribution of epiretinal macrophage-like cells (eMLC) and the objective assessment of ischemic tissue alterations using en face optical coherence tomography (OCT) have not been characterized. This study aimed to quantify eMLC and the optical intensity ratio (OIR) on en face OCT in acute BRAO. METHODS: This retrospective study included 17 patients with unilateral acute BRAO. En face OCT was acquired using a 3 × 3 mm scan pattern centered on the fovea. Structural en face images from a 3-µm slab above the inner limiting membrane were used to identify and quantify eMLC, while slabs at the retinal nerve fiber layer, superficial capillary plexus (SCP), and deep capillary plexus (DCP) were used to measure optical intensity and calculate OIR. eMLC density and OIR were compared between affected and unaffected regions. RESULTS: eMLC density was significantly higher in BRAO eyes than in contralateral eyes across all regions, including the global macula, the affected region and the unaffected region (all p ≤ 0.001). Further analysis showed that eMLC density was higher in the affected region than in the unaffected region (p = 0.015). Global SCP OIR in BRAO eyes was comparable to contralateral eyes (p = 0.113), but global DCP OIR was lower (p = 0.001). OIR in the affected region was higher than in the unaffected region for both SCP and DCP (both p < 0.001). Compared with contralateral eyes, DCP OIR was higher in the affected region (p = 0.013) but lower in the unaffected region (p < 0.001). CONCLUSIONS: En face OCT enables simultaneous assessment of cellular and ischemic changes in acute BRAO, revealing presumed eMLC aggregation in the affected region and a paradoxical OIR pattern. This technique offers a noninvasive platform for evaluating ischemic neuroinflammation, though the OIR findings warrant further investigation.