@article {Loewen044503, author = {Ralitsa T. Loewen and Eric N. Brown and Gordon Scott and Hardik Parikh and Joel S. Schuman and Nils A. Loewen}, title = {Quantification of Focal Outflow Enhancement using Differential Canalograms}, elocation-id = {044503}, year = {2016}, doi = {10.1101/044503}, publisher = {Cold Spring Harbor Laboratory}, abstract = {Purpose: To quantify regional changes of conventional outflow caused by ab interno trabeculectomy (AIT).Methods: Gonioscopic, plasma-mediated ab interno trabeculectomy (AIT; Trabectome, Neomedix, Tustin, CA) was established in enucleated pig eyes. We developed a program to automatically quantify outflow changes (R, package eye-canalogram, github.com) using a fluorescent tracer reperfusion technique. Trabecular meshwork (TM) ablation was demonstrated with fluorescent spheres in 6 eyes before formal outflow quantification with two dye reperfusion canalograms in 6 further eyes. Eyes were perfused with a central, intracameral needle at 15 mmHg. Canalograms and histology were correlated for each eye.Results: The pig eye provided a model with high similarity to AIT in human patients. Histology indicated ablation of TM and unroofing of most Schlemm{\textquoteright}s canal segments. Spheres highlighted additional circumferential and radial outflow beyond the immediate area of ablation. Differential canalograms showed that AIT caused an increase of outflow of 17{\textpm}5 fold inferonasally (IN), 14{\textpm}3 fold superonasally (SN) and also an increase in the opposite quadrants with a 2{\textpm}1 fold increase superotemporally (ST) and 3{\textpm}3 inferotemporally (IT). Perilimbal specific flow image analysis showed an accelerated nasal filling with an additional perilimbal flow direction into adjacent quadrants.Conclusion: A quantitative, differential canalography technique was developed that allows to quantify supraphysiological outflow enhancement by AIT.}, URL = {https://www.biorxiv.org/content/early/2016/03/18/044503}, eprint = {https://www.biorxiv.org/content/early/2016/03/18/044503.full.pdf}, journal = {bioRxiv} }