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Christopher L Passaglia, Kayla Ficarrotta; Effect of continuous eye perfusion on rat aqueous humor dynamics. Invest. Ophthalmol. Vis. Sci. 2017;58(8):3478.
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© ARVO (1962-2015); The Authors (2016-present)
Current methods for inducing glaucoma in animals rely on altering the trabecular meshwork to elevate IOP. We have developed an in-vivo eye perfusion technique for chronically elevating IOP, which causes glaucomatous patterns of retinal ganglion cell loss without experimentally targeting the trabecular meshwork. The aim of this study was to characterize the long-term effects of perfusion-induced ocular hypertension on aqueous humor dynamics.
A fine polyimide tube was implanted in the anterior chamber of one eye of Brown-Norway rats and passed subdermally to a skull mount, which was connected via a tether system to an external reservoir filled with artificial aqueous humor. IOP was continuously measured with an in-line pressure transducer and checked by tonometry. IOP was elevated by 10 mmHg for 9 weeks in six implanted animals. At two-week intervals, the animals were anesthetized with isoflurane and the conventional outflow facility of the implanted eye was measured using a modified constant-pressure perfusion technique with the tethered cannula line connected to a perfusion pump. At the end of the 9-week period, the animal was anesthetized and a 33G needle was inserted into each eye. The cannula line was cut and sealed to prevent leakage, and conventional outflow facility was measured for both eyes using the modified constant-pressure perfusion technique.
Conventional outflow facility did not significantly change in the implanted eye over the 9-week period of IOP elevation. At experiment end, the outflow facility of implanted and control eyes was 0.022 ± 0.002 and 0.024 ± 0.001 µl/min/mmHg, which was not statistically different (p=0.094). Baseline IOP at the start and end of the experiment was not measurably different for implanted and control eyes, further attesting to a lack of permanent or significant damage to the trabecular meshwork.
While chronic IOP elevation can cause glaucomatous damage to the retina, it alone does not appear to impact aqueous outflow pathways. For the conditions tested in rats, no signs of pressure- or flow-induced changes in the biomechanical properties of trabecular meshwork were detected.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
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