Aqueous Angiography in Normal Canine Eyes

Abstract

Purpose To conduct aqueous angiography (AA) using a clinically applicable technique in normal dogs and to compare findings to intravenous scleral angiography (SA). Methods We examined 10 canine cadaver eyes and 12 eyes from live normal dogs. A gravity-fed trocar system delivered 2% sodium fluorescein and 0.25% indocyanine green (ICG) intracamerally (IC) in cadaver eyes. In vivo AA was subsequently performed in one eye of each of the 12 dogs via IC bolus of ICG under sedation. The same 12 dogs received SA via intravenous ICG (mean ± SD) 10.7 ± 3.3 days later. Identical scleral sectors were imaged using a Spectralis confocal scanning laser ophthalmoscope. Results The gravity-fed trocar system permitted visualization of the conventional aqueous humor outflow (CAHO) pathways in cadaver eyes, but not in vivo. Fluorescence was observed superonasally in four of the 10 cadaver eyes within 24.0 ± 3.6 seconds. A single IC bolus of ICG showed CAHO pathways in vivo, demonstrating sectoral outflow patterns in the superotemporal sclera in 10 of the 12 eyes within 35.0 ± 4.3 seconds; four of the 12 eyes exhibited pulsatile aqueous movement. SA exhibited fluorescence patterns comparable to AA with weak pulsatile aqueous humor outflow. Conclusions Angiography (AA or SA) in dogs permits visualization of the CAHO pathway and its vascular components in vivo. AA may be a more useful modality to assess aqueous humor outflow. Translational Relevance Intracameral AA has potential utility for evaluating CAHO in vivo in dogs, an important animal model species .

Development and validation of methods to visualize conventional aqueous outflow pathways in canine primary angle closure glaucoma

“…Enhanced visualization and understanding of distal aqueous humor outflow pathways in at‐risk patients may enable improved treatment planning, tailored to the individual patient. A recent study, published after the present study was completed, presents the use of intracameral injection of fluorescent tracer in normal canine eyes in vivo 30 . Here, we present findings of AA and OCT performed within a controlled range of IOP in normal and PACG‐affected canine eyes, ex vivo, with histologic validation.…”

“…Notably, a recent report of AA in normal canine eyes in vivo, published after the current study was completed, presented inconsistent results in vivo using the cannulation method we used in the current study, but was able to acquire similar delineation of the distal outflow pathway by direct intracameral injection of fluorescent tracer in normal living canine eyes. 30 In contrast to that prior report, 30 in which IOP was not maintained in a consistent range during imaging which limited ability to draw comparisons between eyes and sessions, care was taken in the current study to maintain consistent IOP during imaging by perfusion of BSS or tracer using gravity assisted perfusion from a reservoir. However, this cannot be considered maintenance of true physiological IOP conditions, as there is no venous pressure component in this ex vivo model, and this likely impacts both proximal and distal structures involved in aqueous outflow, including scleral lumens.…”

“…A recent study, published after the present study was completed, presents the use of intracameral injection of fluorescent tracer in normal canine eyes in vivo. 30 Here, we present findings of AA and OCT performed within a controlled range of IOP in normal and PACG-affected canine eyes, ex vivo, with histologic validation.…”

Aqueous angiography in pre‐glaucomatous and glaucomatous ADAMTS10‐mutant canine eyes: A pilot study

“…In this study, pulsatile movement of ICG dye was a frequent observation within intrascleral vessels of ADAMTS10 ‐mutant eyes (7/10; 70% eyes) imaged with AA, as compared to a previous study of normal dogs (4/12; 33%) 4 (Video ). This observation, given 4/7 eyes were hypertensive, could be the direct effect of increasing IOP, creating a surge to drive the choroid piston effect 14…”

Anterior Segment Optical Coherence Tomography Angiography Following Trabecular Bypass Minimally Invasive Glaucoma Surgery

“…When evaluating trabecular bypass MIGS devices, imaging the aqueous outflow tracts may be useful in understanding its efficacy. Aqueous angiography is a functional imaging technique utilising an ab interno approach with fluorescein or indocyanine green (ICG) as tracers, demonstrated in enucleated animal eyes ( 11 , 12 ) and in vivo animal studies ( 13 ). However, aqueous angiography has limited clinical application as it is an invasive procedure that requires intraocular injection of dye, and is associated with potential complications such as infection and anaphylaxis ( 14 ).…”