Aqueous humor dynamics in mice

PURPOSE. To assess aqueous humor dynamics in mouse eyes. METHODS. Aqueous humor dynamics of NIH Swiss White mouse were assessed with an injection and aspiration system, using fine glass microneedles. Intraocular pressure (IOP) was measured by a microneedle connected to a pressure transducer. Episcleral venous pressure (EVP) was measured by gradually lowering intracameral pressure until blood reflux into Schlemm's canal was observed. Outflow facility (C) was determined based on constant pressure perfusion measurements obtained at two different IOPs. Aqueous volume (V-a) was determined by direct measurement of aspirated aqueous humor. Aqueous humor production (F-a) was measured by the dilution method with rhodamine-dextran. Conventional and uveoscleral outflow (F-c and F-u, respectively), as well as the turnover rate of aqueous humor, were also calculated. RESULTS. IOP and EVP were 15.7 +/- 2.0 and 9.5 +/- 1.2 mm Hg, respectively (n = 20). F-a was 0.18 +/- 0.05 muL/min (mean +/- SD; n = 8). C was 0.0051 +/- 0.0006 muL/min per mm Hg (n = 8). Estimated F-c and F-u were 0.032 and 0.148 muL/min, respectively. F-c was 18% of F-a. F-u was 82% of F-a. V-a was 5.9 +/- 0.5 muL (n = 8). The calculated turnover rate of aqueous humor was 2.5%. CONCLUSIONS. The mouse eye has similar aqueous production and aqueous humor turnover rate as the human eye. The presence of both conventional and uveoscleral outflow suggests that the mouse is a useful model system for further investigations of the biology of aqueous dynamics.