Quantification of focal outflow enhancement using differential canalograms

Ralitsa T. Loewen, Eric N. Brown, Gordon Scott, Hardik Parikh, Joel S. Schuman, Nils A. Loewen

    Research output: Contribution to journalArticlepeer-review

    Abstract

    Purpose: To quantify regional changes of conventional outflow caused by ab interno trabeculectomy (AIT). Methods: Gonioscopic, plasma-mediated AIT 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 six eyes before formal outflow quantification with two-dye reperfusion canalograms in six additional eyes. Eyes were perfused with a central, intracameral needle at 15 mm Hg. 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'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 ± 5-fold inferonasally, 14 ± 3-fold superonasally, and also an increase in the opposite quadrants with a 2 ± 1-fold increase superotemporally, and 3 ± 3 inferotemporally. Perilimbal specific flow image analysis showed an accelerated nasal filling with an additional perilimbal flow direction into adjacent quadrants. Conclusions: A quantitative, differential canalography technique was developed that allows us to quantify supraphysiological outflow enhancement by AIT.

    Original languageEnglish (US)
    Pages (from-to)2831-2838
    Number of pages8
    JournalInvestigative Ophthalmology and Visual Science
    Volume57
    Issue number6
    DOIs
    StatePublished - May 1 2016

    Keywords

    • Canalogram
    • Glaucoma
    • Porcine eyes
    • Segmental outflow
    • Trabecular meshwork

    ASJC Scopus subject areas

    • Ophthalmology
    • Sensory Systems
    • Cellular and Molecular Neuroscience

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