Characterizing Macrophage-Like Cells in the Living Human Retina using Clinical OCT.

Abstract

Purpose : Retinal macrophages play important roles in immune and defense regulation. Here we examine macrophage-like cells imaged in the living human retina using a clinical OCT system.

Methods : 17 controls and 1 patient each with diabetic retinopathy, retinal vein occlusion, and multiple sclerosis were imaged using a clinical SD-OCT system (Avanti RTVue-XR; Optovue). Ten 3x3mm scans centered at 9° temporal to the fovea and ten 4.5x4.5mm scans at the ONH were obtained and averaged.^a In controls, repeatability and reproducibility were measured by imaging the temporal retina at 3 times (twice in one day and 3 days apart). A 3µm OCT-reflectance (OCT-R) slab located above [CJ1] [N2] the ILM surface was used for macrophage-like cell density and nearest neighbor distance (NND) measurements (Fig.A1 & B1). An OCT-angiography (OCT-A) located between the ILM and 48µm below the ILM was overlaid with the respective OCT-R slab (Fig. A2 & B2). Cell density and NND measurements were performed on a 500x500µm ROI near the center of the temporal retina and at the supero- and infero-temporal of the ONH OCT-R images. Axial length was obtained for ocular magnification correction of each eye.

Results : In controls, ramified macrophage-like cells with uniform spatial distribution were visualized on the OCT-R images. Motility was observed between images collected on the same day and those collected 3 days apart (Fig. C). There was considerable individual variation in cell density and NND. Mean±SD cell densities measured at the temporal and ONH were 81±26 cells/mm² (range: 44-156 cells/mm²) and 59±16 cells/mm² (range: 32-92 cells/mm²), respectively. Similarly, mean±SD NND measured at the temporal and ONH were 71.5±15.6 µm (range: 52.0-108.8 µm) and 89.5±13.0 µm (range: 62.1-130.5 µm), respectively. Non uniform spatial distribution and altered morphology of the macrophage-like cells were identified in patients with retinopathies.

Conclusions : Our findings showed uniform spatial distribution and morphology of macrophage-like cells on the surface of the ILM with apparent motility over time in healthy controls. Their distribution and morphology suggests an origin of macrophage-like cells such as microglia or hyalocytes.^b Further studies should focus on the functions and dynamics of these cells in controls and patients with retinopathies.

This is a 2020 ARVO Annual Meeting abstract.