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Purpose: The study aimed to provide a quantitative description of aqueous humor dynamics in healthy rat eyes.

Methods: One eye of 26 anesthetized adult Brown-Norway rats was cannulated with a needle connected to a perfusion pump and pressure transducer. Pressure-flow data were measured in live and dead eyes by varying pump rate (constant-flow technique) or by modulating pump duty cycle to hold intraocular pressure (IOP) at set levels (modified constant-pressure technique). Data were fit by the Goldmann equation to estimate conventional outflow facility and unconventional outflow rate. Parameter estimates were respectively checked by inserting a shunt of similar conductance into the eye and by varying eye hydration methodology.

Results: Rat IOP averaged 14.6 ± 1.9 mm Hg at rest. Pressure-flow data were repeatable and indistinguishable for the two perfusion techniques, yielding 0.096 ± 0.024 μL/min. was similar for live and dead eyes and increased upon shunt insertion by an amount equal to shunt conductance, validating measurement accuracy. At 100% humidity, and trabecular anatomy looked normal.

Conclusions: Rat aqueous humor dynamics are intermediate in magnitude compared to those in mice and humans, consistent with species differences in eye size even when eyes are not enucleated. Absence of washout is a notable finding seen only in mouse and human eyes to date.

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Investigative Ophthalmology & Visual Science, v. 59, issue 6, p. 2529-2537