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Lihua Gong, Elliot D K Cha, Haiyan Gong; Hydrodynamic and Morphological Changes along the Trabecular Outflow Pathway in POAG Eyes. Invest. Ophthalmol. Vis. Sci. 2016;57(12):5141.
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© ARVO (1962-2015); The Authors (2016-present)
This study aimed to determine outflow patterns and morphological changes responsible for decreased outflow facility (C) in eyes with primary open angle glaucoma (POAG) compared to normal eyes.
Five POAG and six normal enucleated human eyes were perfused for 30 minutes at 15mmHg to establish a baseline C. The anterior chamber of each eye was exchanged (5ml) and perfused with a fixed volume (200µl) of fluorescent tracer to label outflow patterns. The anterior segment of each eye was obtained, globally imaged and dissected radially into 16 wedges, from which the frontal sections were cut and imaged with confocal microscopy. Percent effective filtration area (EFA) was calculated from the measured lengths of tracer distribution in the trabecular meshwork (TM), episcleral veins (ESV), and along the inner wall (IW) of Schlemm’s canal. TM thickness was measured. Numbers of CCs and percentage of herniation into CC ostia were analyzed. The same sections were further processed for light and electron microscopy. Student’s t-test and correlation analysis were performed.
C was significantly lower in POAG eyes than normal eyes (p<0.01), which was associated with a significant decrease in EFA (p<0.01) in all three regions (TM, IW and ESV). In both POAG and normal eyes, significantly higher EFA was found in the TM than IW and ESV (p<0.01); EFA in the latter two were similar. EFA in ESV was positively correlated with C in all eyes (R=0.629, p<0.05). Mean TM thickness significantly decreased in POAG compared to normal eyes (p<0.01). Nasal quadrants showed preferential outflow in both normal and POAG eyes compared to the other quadrants, which was associated with a greater regional TM thickness. However, the difference in TM thickness reached statistical significance only in normal eyes. Greater percent herniation into CC ostia was found in POAG compared to normal eyes (p<0.05). More TM endothelium loss, extracellular matrix accumulation in the trabecular beams, and beam fusion were observed in POAG eyes.
Preferential outflow found in the nasal quadrants of normal and POAG eyes is associated with increased regional TM thickness. Significant reduction in EFA contributes to decreased C in POAG eyes, which is a result of morphologic changes including more compact TM, more herniation-blocked CCs, and TM beam fusion due to loss of endothelial covering.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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