Greater Outflow Facility Increase After Targeted Trabecular Bypass in Angiographically Determined Low-low Regions

Abstract

To investigate the impact of trabecular bypass surgery targeted to angiographically determined high- vs. low-aqueous humor outflow areas on outflow facility (C) and intraocular pressure (IOP). Exvivo comparative study. Postmortem exvivo porcine and human eyes. Porcine (n=14) and human (n=13) whole globes were acquired. In both species, anterior segments were dissected, mounted onto a perfusion chamber, and perfused using Dulbecco's phosphate buffered solution containing glucose in a constant flow paradigm to achieve a stable baseline. Fluorescein was perfused into the anterior chamber and used to identify baseline segmental high- and low-flow regions of the conventional outflow pathways. The anterior segments were divided into 2 groups, and a 5 mm needle goniotomy was performed in either a high- or low-flow area. Subsequently, C and IOP were quantitatively reassessed and compared between surgery in baseline "high-flow" and "low-flow" region eyes followed by indocyanine green angiography. Outflow facility. In all eyes, high- and low-flow segments could be identified. Performing a 5-mm goniotomy increased outflow facility to a variable extent depending on baseline flow status. In the porcine high-flow group, C increased from 0.31±0.09 to 0.39±0.09 μL/mmHg/min (P=0.12). In the porcine low-flow group, C increased from 0.29±0.03 to 0.56±0.10 μL/mmHg/min (P<0.001). In the human high-flow group, C increased from 0.38±0.20 to 0.41±0.20 μL/mmHg/min (P=0.02). In the human low-flow group, C increased from 0.25±0.11 to 0.32±0.11 μL/mmHg/min (<0.001). There was statistically significant greater increase in C for eyes where surgery was targeted to baseline low-flow regions in both porcine (0.07±0.09 vs. 0.27±0.13, P=0.007 μL/mmHg/min, high vs low flow) and human eyes (0.03±0.03 vs. 0.07±0.02, P=0.03 μL/mmHg/min, high vs. low flow). Targeting surgery to low-flow areas of the trabecular meshwork yields higher overall facility increase and IOP reduction compared to surgery in high-flow areas. Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.