Erythrocyte Mediated Angiography: Use of a Novel Method to Determine Erythrocyte Dynamics in the Glaucomatous Optic Nerve

Abstract

Purpose : Impaired optic nerve blood flow may play a significant role in the development and progression of open angle glaucoma. Prior work has focused on the relationship between glaucoma and bulk blood flow or blood velocity, which has certain limitations in determining the metabolic activity and oxygenation of a given capillary bed. Erythrocyte Mediated Angiography (EMA) is a novel technique that permits direct visualization of ICG-labelled ghost erythrocytes in vivo, to study ocular blood flow. Prior work shows that Non-Human Primates with experimentally induced glaucoma show impaired vasomotion which manifests as proportionally fewer paused erythrocytes. EMA may prove to be a more sensitive marker of ocular blood flow than prior methodologies, and could potentially become a biomarker for development and progression of glaucoma. We present data on the safety and efficacy of this technique for assessment of erythrocyte pausing in the optic nerve head of glaucoma patients and healthy controls.

Methods : Glaucoma patients were recruited from glaucoma clinic and healthy controls from optometry clinic. EMA was performed using a Heidelberg HRA 2 Scanning Laser Ophthalmoscope (Heidelberg Engineering, Heidelberg Germany). Twelve to fifteen second angiograms of the optic disc of each individual were then graded to assess the presence and degree of erythrocyte pausing in the optic disc.

Results : Twenty-five eyes of fourteen patients underwent Erythrocyte Mediated Angiography, 6 with diagnoses of glaucoma or glaucoma suspect and 8 normal controls. This was followed by conventional ICG Angiography. One patient had a syncopal event associated with the conventional ICG angiography, but otherwise tolerated EMA without complication. Image quality was too poor in two eyes to determine if there was erythrocyte pausing in the optic nerve head. 18 of the remaining 23 eyes showed evidence of erythrocyte pausing in the optic nerve head (Figure 1, Figure 2). All 25 eyes showed evidence of erythrocyte pausing in the peripapillary retina.

Conclusions : Vasomotion is the periodic pausing of erythrocytes in capillaries. Impairment of vasomotion is thought to play a role in the pathogenesis of diabetic macular edema and other retinal vascular diseases. This work is the first to our knowledge to describe this physiologic phenomenon in the human optic nerve head in both patients with glaucoma and controls.

This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.