Imaging Canine Post-Trabecular Aqueous Outflow Pathways: Effect of Acute Intraocular Pressure Elevation in Normal Eyes.

Acute IOP elevation causes structural collapse of canine post-trabecular outflow vessels.

This ex vivo study examined how acute intraocular pressure (IOP) elevation affects the post-trabecular aqueous outflow pathway structure in normal canine eyes using advanced imaging techniques. Nineteen eyes were evaluated using aqueous angiography (AA) and anterior segment optical coherence tomography (OCT) at physiologic IOP (10-25 mmHg) and elevated IOP (55-68 mmHg) for 30-120 minutes. Researchers measured scleral lumen heights (SLH) of vascular profiles and characterized outflow regions as high-flow or low-flow based on angiographic signal intensity. Key findings demonstrated that segmental AA outflow correlated with lumens visible on OCT scans at normal pressure. However, acute IOP elevation caused significant scleral lumen collapse, with large vessels collapsing more than small vessels. Statistical analysis confirmed significantly reduced SLH after both 30 and 120 minutes of IOP elevation (p < 0.0001), and high-flow regions determined by AA were substantially reduced. These findings suggest pressure-dependent structural changes in the post-trabecular outflow pathway, with potential implications for understanding glaucomatous disease progression and developing novel diagnostic and therapeutic approaches in canine glaucoma.

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