Differences in epiretinal macrophage-like cells and associated retinochoroidal changes between multifocal choroiditis...

To investigate the features of epiretinal macrophage-like cells (eMLC) and retinochoroidal parameters in multifocal choroiditis (MFC) and punctate inner choroidopathy (PIC) by using widefield optical coherence tomography angiography (WF-OCTA).

This retrospective cross-sectional study included 16 eyes from 11 patients with MFC, 16 eyes from 13 patients with PIC, and 16 eyes from 16 matched healthy controls. The eMLC was semi-automatically segmented and quantified on en face optical coherence tomography (OCT) images, derived from a 3-μm slab on the inner limiting membrane. From the corresponding 24 × 20 mm retina scan area, retinochoroidal parameters were measured using WF-OCTA.

Eyes with MFC exhibited a significantly greater number and density of eMLC compared with both eyes with PIC and healthy control eyes (all P < 0.05). Furthermore, compared to the PIC eyes, the MFC eyes demonstrated significantly greater thickness of the inner retinal layer, outer retinal layer, total retina, and choroid (all P < 0.05). Choroidal structural analysis revealed that both choroidal capillary density (CCD) and choroidal vessel volume (CVV) were also significantly higher in MFC eyes than in PIC and control eyes (all P < 0.05). In contrast, no significant differences were observed in any of the measured retinochoroidal parameters between the PIC and control eyes. While there was no significant difference in retinal thickness of typical lesion between the MFC and PIC groups, the choroidal thickness of typical lesion was markedly greater in patients with MFC (P < 0.05). Furthermore, a significant positive correlation was identified between eMLC density and RT within the MFC group. A subgroup analysis focusing on disease activity demonstrated that MFC eyes with active leakage on fundus fluorescein angiography (FFA) had significantly higher eMLC density, inner retinal thickness, total retinal thickness, choroidal thickness, and CVV than eyes without FFA leakage (P < 0.05 for all).

The MFC group demonstrated a significantly greater eMLC density, increased retinochoroidal thickness, and higher density of the choroidal vasculature compared to both the PIC and control groups, between which there were no significant differences. These findings indicate that MFC represents a diffuse, full-thickness retinochoroidal inflammatory process, in contrast to the more localized inflammation characteristic of PIC. Besides, the eMLC may serve as a non-invasive indicator for assessing the severity of fluorescein leakage and retinal inflammation in MFC, offering an objective tool for longitudinal monitoring.