Clinical Imaging of Macular Surface Macrophages in Retinal Vasculopathies – Automated OCT Cell Density Mapping and Adaptive Optics Microscopy

Abstract

Purpose : To compare macular surface macrophage density and associated capillary density in the vasculopathic and normal retinas using clinical OCT, and to examine microanatomic features of the same cells using adaptive optics SLO.

Methods : 49 patients with diabetic retinopathy (DR) (49 eyes), 12 with Sickle Cell Retinopathy (12 eyes), 10 with Retinal Vein occlusion (10 eyes) and 14 controls (14 eyes) were imaged using clinical SD-OCT (Avanti RTVue-XR; Optovue). Ten 3x3mm foveal centered scans were acquired, averaged and corrected for axial length. FAZ border was outlined manually on the OCT-A scan. Automated surface macrophage cell density measurements within the FAZ were performed on the 3µm OCT-R slab above the ILM surface using MATLAB and cell density maps were generated. OCT-A capillary densities were measured on full vascular slabs, from the ILM to 9µm below the posterior boundary of the OPL. Quad Detection Adaptive Optics SLO imaging was performed to characterize the morphologic features of the cells in select subjects.

Results : Surface macrophage cells were found within the FAZ in 80% of diabetic eyes, 86% of SCR eyes and 90% of RVO eyes, and 31% of controls. Statistically significant differences were observed between vasculopathy groups and controls in surface macrophage cell density (Kruskal-Wallis tests, P= 0.0005) with mean±SDs of 5±5 6±7, 13±10, and 1±1 cells/mm2 in SCR, DR, RVO and control groups, respectively. Linear regression found significant inverse correlation between surface macrophage cell densities within the FAZ and perifoveal perfused capillary densities (R= -0.22, P= 0.037). Adaptive optics imaging revealed delicate microscopic features of cell morphology inaccessible at the resolution of clinical imaging.

Conclusions : Clinical OCT is capable of detecting and mapping the density of macular surface macrophage cells in vasculopathic as well as normal eyes. The association of Increased FAZ cell density with corresponding reduced perifoveal capillary density suggests an ischemic stimulus. Adaptive Optics SLO imaging confirms the character and morphology of these cells and suggests their potential value a clinical biomarker of progressive retinal vascular disease or response to therapy.

This is a 2021 Imaging in the Eye Conference abstract.

 

Macular surface macrophages cells and microvasculature of a control and an RVO patient

 

OCT-R/OCT-A clinical image vs Adaptive optics SLO microscopy