Aqueous humor dynamics in the aging human eye

PURPOSE: Healthy subjects were recruited to identify normal, age-associated changes in intraocular pressure and aqueous humor dynamics, METHODS: Normal healthy subjects from two age groups were enrolled in the s tudy: (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 pneumatonomet ry, tonographic outflow facility by pneumatonography, and episcleral venous pressure by venomanometry, Aqueous flow and outflow facility were determin ed by a fluorophotometric technique. Uveoscleral outflow and anterior chamb er volume were calculated, Results from the older group were compared with those from the younger group by means of unpaired, two-tailed t tests. RESULTS: Compared with the younger group, the older group showed significan t differences as follows: smaller anterior chamber volume (160 +/- 39 vs 24 7 +/- 39 mu l; mean +/- SD; P <.00001), reduced aqueous flow (2.4 +/- 0.6 v s 2.8 +/- 0.8 mu l/minute; P = .002), and reduced uveoscleral outflow (1.10 +/- 0.81 vs 1.52 +/- 0.81 mu l/minute; P = .009), CONCLUSIONS: In the healthy aging eye, there is a reduction in the producti on of aqueous humor and a reduction in its drainage through the uveoscleral outflow pathway, (Am J Ophthalmol 1999;127:407-412, (C) 1999 by Elsevier S cience Inc. All rights reserved.).