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Kayla Ficarrotta, Simon Bello, Christopher L Passaglia; Aqueous humor dynamics in the Brown-Norway rat. Invest. Ophthalmol. Vis. Sci. 2016;57(12):6453.
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© ARVO (1962-2015); The Authors (2016-present)
The dynamics of aqueous humor drainage are affected in glaucomatous eyes. The purpose of this study was to quantify the properties of aqueous outflow mechanisms in healthy Brown-Norway rats, a popular animal model for glaucoma research. These properties include IOP, aqueous humor formation rate (Fin), episcleral venous pressure (EVP), conventional outflow facility (C), and unconventional outflow facility (Fun).
The anterior chamber of 17 adult Brown-Norway rat eyes was cannulated with a 33G needle or chronically implanted with a polyimide tube. The cannula was connected to a perfusion pump and pressure transducer for continuous IOP modulation and recording. C was measured in anesthetized animals via a constant-rate perfusion technique or a new modified-constant-pressure perfusion technique. Outflow experiments were then repeated in situ on 6 euthanized animals to derive Fun and the inflow due to EVP and Fin. Additional control experiments were performed to examine hysteresis effects, washout rate, and anatomical changes associated with extended perfusions.
Resting IOP was 14.8 ± 1.6 mmHg. C was measured to be 0.0229 ± 0.0017 µl/min/mmHg and 0.0251 ± 0.0014 µl/min/mmHg for the live and dead eye, respectively. These values are not statistically different. Constant-rate perfusion and modified constant-pressure perfusion methodologies resulted in C of 0.0240 ± 0.0019 µl/min/mmHg and 0.0239 ± 0.0020 µl/min/mmHg, respectively. These values are not statistically different. Fun was derived to be 0.0970 ± 0.0188 µL/min. The inflow resulting from EVP and Fin was 0.4652 ± 0.0487 uL/min. A paired t-test demonstrated that there is no statistically significant difference between C measured by incremented versus decremented IOP or perfusion rates (P=0.808, n=3). The measured washout rate was not statistically different from zero. No anatomical changes of macroscopic aqueous humor outflow structures were observed in hematoxylin and eosin stained histological sections.
We have developed a reliable method for evaluating aqueous humor dynamics and established baseline values in healthy Brown-Norway rats with which to assess effects of glaucoma on aqueous drainage.
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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