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Sri Meghana Konda, Julie A Kiland, Jared McDonald, Murray A Johnstone, Paul L Kaufman; Real-time optical imaging of Schlemm’s canal and distal outflow structures in live monkeys. Invest. Ophthalmol. Vis. Sci. 2020;61(7):3428.
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© ARVO (1962-2015); The Authors (2016-present)
We describe an accurate, dynamic real-time imaging technique to characterize behavior of the distal outflow structures in non-human primates (NHPs) in response to changes in intraocular pressure (IOP). This may enhance our understanding of human glaucoma pathophysiology and help evaluate therapeutics.
1. A needle, connected to a pressure transducer and computer, is placed into the anterior chamber of an anesthetized monkey to continuously record and control IOP. Concurrently, SC is imaged using a non-invasive, non-contact endoscope attached to a digital camera that is connected to a computer. The images obtained are time-synchronized with the collection of IOP data, so that the corresponding IOP is known for every frame of the video as it displays outflow pathway (OP) configuration and coloration.2. To characterize the changes in SC, we picked ten images at equal intervals and different IOPs from the video (five at increasing pressure points and five at decreasing pressure points). Using ImageJ, we selected a Region of Interest (ROI), which was applied to all ten images. We chose a particular color threshold to highlight just the SC in the ROI. We measured the percent area of SC (PAS) highlighted in the total ROI, as IOP was altered.
1. As IOP is lowered, SC fills with venous blood and is visible as a red band. When IOP is raised, SC narrows and blanches. These changes occur at a wider and greater IOP range than predicted (~5-22mmHg). A sausage-like appearance of the blood column within SC is observed, which may indicate segmental/regional differences or confluence with collector channels (CC). With image processing, CCs and intrascleral vessels are visible. Blood-tinged aqueous is seen passing through the distal connections between SC and CC in synchrony with the ocular pulse. The dimensions of the CCs are notably IOP-dependent. At low IOP, CCs are distended and visible but at high IOP are seen to undergo collapse. Subtle circumferential flow of the blood column within SC is may be seen.2. As IOP is increased PAS decreases. Furthermore, an inverted bell-shaped curve is seen indicating the decrease and increase in PAS as we increase and decrease IOP, respectively.
Our video recording of OP morphology while digitally recording IOP provides synchronized time stamping and a useful description of pressure-related pathway dynamics.
This is a 2020 ARVO Annual Meeting abstract.
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