Assessing peripapillary surface macrophage density in eyes with glaucomatous damage using enface OCT

Abstract

Purpose : To detect and quantify peripapillary surface macrophage density changes in patients with open angle glaucoma (OAG) using enface OCT-reflectance (OCT-R) images.

Methods : 27 controls and 12 moderate to severe OAG patients were imaged using a clinical SDOCT system (Avanti RTVue-XR; Optovue). Ten 4.5x4.5mm scans centered at the optic nerve head (ONH) were obtained and averaged (PMID: 32574351). Seven eyes of 6 OAG patients were imaged at two visits 11-29 months apart. Semi-automated macrophage cell identification was performed on a 3 µm OCT-R slab located between 3 and 6 µm above the ILM using MATLAB (PMID: 32574351). An annular ROI with 0.75mm in width centered at the ONH was created on the OCT-R image (PMID: 29795576) (Fig). This annular ROI was then divided into four quadrants (temporal, nasal, superior and inferior) for macrophage density measurements. Cell density maps were also generated for each subject to allow rapid visualization of cell distribution across the ONH area. Axial length was obtained for ocular magnification correction of each image.

Results : In control eyes, the highest cell density was found in the temporal quadrant with mean±SD of 35.7±12.6 cells/mm² followed by the nasal (23.4±7.3 cells/mm²), inferior (23.1±7.6 cells/mm²), and superior (22.9±9.4 cells/mm²). In the OAG eyes, the highest cell density was found in the temporal quadrant with mean±SD of 16.6±13.2 cells/mm² followed by the nasal (15.6±8.3 cells/mm²), superior (12.6±4.8 cells/mm²), and inferior (9.9±6.3 cells/mm²). Cell densities measured at 4 quadrants were significantly reduced in eyes with OAG (Mann-Whitney rank tests, P values <0.05). Focal loss of surface macrophages was observed at regions with retinal nerve fiber bundle (RNFB) defect progression in OAG eyes (Fig). Density mapping of peripapillary surface macrophages enabled us to quantitatively and visually identify this novel feature of progressive RNFB defects.

Conclusions : Clinical OCT is capable of imaging surface macrophages on the ILM in control and glaucoma eyes. Density of these cells appeared reduced in regions with glaucomatous damage. Characterizing the relationship between surface macrophage density and the underlying retinal nerve fiber integrity may be a useful biomarker for active disease progression, and possibly response to treatment.

This is a 2021 ARVO Annual Meeting abstract.