Pattern of peripapillary capillary density loss in ischemic optic neuropathy compared to that in primary open-angle glaucoma

Abstract

Purpose: Both non-arteritic anterior ischemic optic neuropathy (NAION) and primary open-angle glaucoma (POAG) damage retinal ganglion cell axons, which are perfused by the radial peripapillary capillaries. To evaluate the pattern of ischemia, we compared peripapillary capillary density (PCD) in NAION eyes to POAG eyes matched for visual field mean deviation and retinal nerve fiber layer thickness.

Methods: 31 chronic NAION (>6 months after the acute event) and unaffected fellow eyes (31 subjects), 42 moderate and severe POAG eyes (27 subjects), and 77 control eyes (46 healthy subjects) were imaged with a commercial optical coherence tomography angiography system (AngioVue, Avanti RTVue-XR, Optovue, CA) at two academic institutions. Two concentric circles of diameters 1.95mm (inner) and 3.45mm (outer) were manually placed on images centered on the optic nerve head, producing an annular region-of-interest. Image analysis with major vessel removal was performed using a custom program. Whole-image, whole-annulus, and sectoral PCDs were measured.

Results: Whole-image and whole-annulus PCDs in NAION and moderate and severe POAG eyes were significantly decreased compared to unaffected fellow eyes and control eyes (all P<0.001). Superior and temporal PCD values were affected more than other sectors in both NAION and POAG groups compared to control group. Whole-image and whole-annulus PCDs were not statistically different between NAION and POAG eyes (both P = 0.99). However, of all peripapillary sectors, the inferior sector PCD value was less affected in POAG eyes compared to NAION eyes (P = 0.001). Univariate analysis results also revealed a significant positive correlation between superior and inferior PCDs and corresponding RNFL thicknesses. The inferior sector correlation was greater in POAG than NAION eyes.

Conclusion: While the whole PCD values were not different in chronic NAION and POAG, the greater correlation of inferior PCD with corresponding RNFL sectors in POAG compared to NAION suggests greater susceptibility of the inferior radial peripapillary capillary in the pathogenesis of POAG.

Fig 1. Peripapillary capillary density maps.

Comparisons of peripapillary capillary density maps in a normal, an anterior ischemic optic neuropathy (AION) eye with average retinal nerve fiber layer (RNFL) thickness of 54 μm and visual field mean deviation of -20.5 dB, and a severe primary open-angle glaucoma (POAG) eye with average RNFL thickness of 49 μm and mean deviation of -25.2 dB. First column: grayscale OCT-A images with two concentric circles with 1.95-mm (inner) and 3.45-mm (outer) diameters, Second column: Perfused capillary area (in cyan) after the removal of major blood vessels. Third column: corresponding color-coded perfused capillary density maps with numerical capillary density (%) in peripapillary ring in four quadrants.