Aqueous humor dynamics in ocular hypertensive patients.
OBJECTIVE
To evaluate the mechanism of the intraocular pressure (IOP) elevation in ocular hypertension (OHT), aqueous humor dynamics were compared in patients with OHT versus age-matched ocular normotensive (NT) volunteers.


METHODS
In this retrospective study, one group included patients diagnosed with OHT (IOPs > 21 mm Hg, n = 55) for at least six months. All eye medications were discontinued for at least three weeks before the study visit. A second group included age-matched NT subjects (n = 55) with no eye diseases. The study visit included measurements of IOP by pneumatonometry, aqueous flow and outflow facility by fluorophotometry, anterior chamber depth and corneal thickness by pachymetry and episcleral venous pressure by venomanometry. Uveoscleral outflow and anterior chamber volume were calculated mathematically.


RESULTS
Significant differences in the OHT versus the NT groups were as follows: increased IOP (21.4 +/- 0.6 versus 14.9 +/- 0.3 mm Hg, respectively; P < 0.0001), reduced uveoscleral outflow (0.66 +/- 0.11 versus 1.09 +/- 0.11 microL/min; P = 0.005) and reduced fluorophotometric outflow facility (0.17 +/- 0.01 versus 0.27 +/- 0.02 microL/min/mm Hg; P < 0.0001). With respect to age, anterior chamber volume decreased in both groups at a rate of 2.4 +/- 0.3 microL/year (r(2) = 0.5, P <.001) and aqueous flow decreased at a rate of 0.013 +/- 0.005 microL/min/year (r(2) = 0.07, P = 0.005).


CONCLUSIONS
The increased IOP in ocular hypertensive patients is caused by a reduction in trabecular outflow facility and uveoscleral outflow. Aqueous flow remains normal. When both ocular normotensive and hypertensive groups are combined, aqueous flow and anterior chamber volume decrease slightly with age.
Toris
Carol B
CB
Department of Ophthalmology, University of Nebraska Medical Center, Omaha, Nebraska 68198-5540, USA. ctoris@unmc.edu
Koepsell
Scott A
SA
Yablonski
Michael E
ME
Camras
Carl B
CB
D000328:Adult; D000368:Aged; D001082:Aqueous Humor / Q000378:metabolism*; D005260:Female; D015590:Fluorophotometry; D006801:Humans; D007429:Intraocular Pressure; D008297:Male; D008875:Middle Aged; D009798:Ocular Hypertension / Q000378:metabolism*; D012189:Retrospective Studies; D012590:Sclera / Q000378:metabolism; D014129:Trabecular Meshwork / Q000378:metabolism; D014602:Uvea / Q000378:metabolism; D014690:Venous Pressure