Aqueous Angiography: Real-time, Live Human and Non-Human Primate Aqueous Humor Outflow Imaging

Abstract

Purpose : To evaluate aqueous humor outflow (AHO) in intact eyes of living humans and non-human primates (NHP) using aqueous angiography

Methods : Aqueous angiography was performed for the first time in intact eyes of living subjects (6 NHP and one living human [73 yo male during cataract surgery]). After anesthesia, an anterior chamber (AC) maintainer was placed through a temporal 1 mm side-port wound. Indocyanine green (ICG; 0.4%) or 2.5% fluorescein was introduced (individually or in sequence) into the eye with a gravity-driven constant-pressure system. Aqueous angiography images were obtained with a Heidelberg Spectralis HRA+OCT suspended over the eye using a custom designed surgical boom arm (FLEX module). For NHPs, anterior segment optical coherence tomography (OCT) images were taken comparing angiographically positive and negative regions.

Results : In NHP, aqueous angiography positive signal co-localized with episcleral veins as identified by infrared imaging (Fig. 1). Areas with aqueous angiography signal also showed intrascleral lumens using anterior segment OCT. Sequential aqueous angiography in individual eyes with ICG followed by fluorescein showed similar, segmental, and mostly stable patterns. A pulsatile nature of angiographic AHO was sometimes seen. Aqueous angiographic patterns could also sometimes dynamically change. In some cases, regions without aqueous angiography signal could develop signal. Alternatively, angiographic signal could also suddenly disappear from regions in which angiographic signal was initially documented. In the living human subject, aqueous angiography was successfully performed with demonstrating segmental patterns with no adverse sequelae

Conclusions : Aqueous angiography was conducted for the first time in intact eyes of living NHPs and one human subject demonstrating segmental and pulsatile patterns. The ability for angiographic AHO patterns to dynamically shift and move in the intact eye of a living NHP was a new discovery. Real-time imaging of AHO improves our understanding of the eye and may have surgical glaucoma treatment implications.

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

 

Figure 1. A) Infrared reflectance image of a NHP right eye shows episcleral veins (black arrows). B) Aqueous Angiography signal from the same eye (white arrows). C) Image overlap shows good correspondence between aqueous angiography signal and episcleral veins.