Strain and Age Effects on Aqueous Humor Dynamics in the Mouse

We evaluated differences in aqueous humor dynamics (AHD) among several mouse strains within younger and older age groups.

Albino (A/J, BALB/cJ) and pigmented (C3H/HeJ, C57-BL/6J) mice (young [2½-4½ months] and aged [10-12 months]) were studied. Intraocular pressure (IOP) was measured. In cannulated eyes, episcleral venous pressure (Pe) was assessed (blood reflux). Other AHD parameters (outflow facility [C], aqueous humor formation rate [Fin]) were assessed (constant flow infusion). Uveoscleral outflow rate (Fu) was obtained by calculation (Fu(calc)) using the modified Goldmann equation, and in additional eyes (for comparison), by FITC-dextran perfusion (Fu(FITC-dex)).

Intraocular pressure was higher in pigmented strains, but did not exhibit age-dependence, except in the C57-BL/6J strain. Fu(calc) decreased with age in BALB/cJ (↓83.3%), C3H/HeJ (↓78.0%), and C57-BL/6J (↓85.0%) strains. In the A/J strain, Fu(calc) decreased with age (↓70.0%), but not significantly. Fin decreased with age in the C3H/HeJ (↓53.6%) strain. In C57-BL/6J and A/J strains, Fin decreased with age, but not significantly. C in the BALB/cJ strain increased with age (↑62.5%). In C3H/HeJ and C57-BL/6J strains, C increased with age, but not significantly. Episcleral venous pressure ranged from 6.0 to 6.6 mm Hg (albino strains) to 8.5 to 8.9 mm Hg (pigmented strains). Pe was not age dependent, but was higher in pigmented animals.

In mouse, Fu and Fin diminish with age. C tends to increase as animals progress to middle life. There are strain differences in Fu, IOP, C, Fin, and Pe. The current findings provide an important foundation for comparisons among different strains in different study reports.