Healthy subjects were recruited to identify normal, age-associated changes in intraocular pressure and aqueous humor dynamics.

Normal healthy subjects from two age groups were enrolled in the study: (1) those from 20 to 30 years of age (n = 51) and (2) those 60 years of age and older (n = 53). Intraocular pressure was measured by pneumatonometry, tonographic outflow facility by pneumatonography, and episcleral venous pressure by venomanometry. Aqueous flow and outflow facility were determined by a fluorophotometric technique. Uveoscleral outflow and anterior chamber volume were calculated. Results from the older group were compared with those from the younger group by means of unpaired, two-tailed t tests.

Compared with the younger group, the older group showed significant differences as follows: smaller anterior chamber volume (160 ± 39 vs 247 ± 39 μl; mean ± SD; P < .00001), reduced aqueous flow (2.4 ± 0.6 vs 2.8 ± 0.8 μl/minute; P = .002), and reduced uveoscleral outflow (1.10 ± 0.81 vs 1.52 ± 0.81 μl/minute; P = .009).

In the healthy aging eye, there is a reduction in the production of aqueous humor and a reduction in its drainage through the uveoscleral outflow pathway.