OCT-Angiography and Aqueous Angiography Visualization of Aqueous Humor Outflow in Human Anterior Segment Perfusion Eyes.

Abstract

Purpose : To visualize aqueous humor outflow (AHO) in human anterior segments using optical coherence tomography angiography (OCTA) with lipid emulsion (LE) simultaneous to aqueous angiographic imaging using fluorescein.

Methods : Post-mortem human eyes were acquired from the San Diego Eye Bank under IRB approval (n=4) without known ocular diseases or prior surgery. Anterior segments were dissected, mounted onto a perfusion apparatus, and perfused with DPBS (2.5µl/min) until a stabile baseline outflow facility was achieved. The perfusion setup was flushed with a mixture of fluorescein (2%; Akorn) and LE (10%; Baxter Healthcare) diluted in DPBS with the anterior chamber open to atmospheric pressure. The eye was pressurized again, and fluorescein angiography was performed at set time points to visualize segmental high-AHO (HF) and low-AHO (LF) areas. OCTA was performed using the retinal OCTA function on the Heidelberg Spectralis HRA+OCT on areas of pre-identified aqueous angiography HF and LF regions (A-scan depth of 1.9 mm, a full-width 3.0 mm in tissue and a total 256 B scans). Images were exported in TIFF format and further processed and analyzed using ImageJ/FIJI software. The AHO patterns in aqueous angiographic HF and LF areas were generated by volumetric rendering of selected B-scan stacks.

Results : In all eyes, aqueous angiography demonstrated the presence of focal HF and LF regions. High temporal fluctuation of lipid emulsion-derived OCT signal allowed for OCT angiography of the perfused LE. Distinct superficial OCTA microvasculature was observed in projection-resolved images, and portions of suspected Schlemm’s canals were identified (Fig. 1). LF aqueous angiographic regions were devoid of OCTA signal.

Conclusions : LE-based OCTA may be useful in combination with aqueous angiography to perform a structure:function analysis of AHO pathway structural features that indicate regions of HF and LF AHO.

This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.

 

Fig. 1: Example an anterior segment OCTA image from an aqueous angiography-defined high-flow region from a human eye. Volumetric rendering of a 125 B-scan stack. Suspected Schlemm’s canals (white arrows) and collector channels (white arrowheads)