purpose. To assess the early effect of latanoprost on outflow facility and aqueous humor dynamics in the mouse.

methods. Aqueous humor dynamics in NIH Swiss White mice were assessed with an injection and aspiration system, using fine glass microneedles. A single 200-ng (4 μL) dose of latanoprost was applied to one eye 2 hours before measurement. The fellow eye served as a control. Intraocular pressure (IOP) was measured by using an established microneedle procedure. Outflow facility (C) was determined by constant-pressure perfusion measurements obtained at two different IOPs. Aqueous humor flow (Fa) was determined by a dilution method using rhodamine-dextran. Conventional and uveoscleral outflow (Fc and Fu) were calculated by the Goldmann equation.

results. Average IOP, Fa, and C of control eyes were 15.7±1.0 mm Hg, 0.144±0.04 μL/min (mean±SD, n= 8), and 0.0053±0.0014 μL/min per mm Hg (n= 21), respectively. Average IOP, Fa, and C of treated eyes were 14.0±0.8 mm Hg, 0.138±0.04 μL/min (n= 8 for each), and 0.0074±0.0016 μL/min per mm Hg (n= 21), respectively. The differences between treated and control eyes were significant for IOP and total outflow facility only.

conclusions. These data indicate that the early hypotensive effect of latanoprost in the mouse eye is associated with a significant increase in total outflow facility. Alterations in the aqueous dynamics induced by latanoprost can be measured reproducibly in the mouse and may provide a useful model for further determining the mechanism by which latanoprost reduces IOP and alters outflow facility.