A test that was common in the 1960's and was used to detect primary open angle glaucoma was the water drinking test (patients drank 1 quart of water to stress the fluid drainage mechanism of the eyes. Intraocular pressure was then measured over the next hour). Recently this test has been demonstrated as a predictor of peak eye pressure during the day. The purpose of this study is to compare the results of the water drinking test between eyes that have undergone trabeculectomy and eyes that have undergone tube shunt surgery.

Inclusion Criteria:

• prior trabeculectomy or tube shunt for the treatment of glaucoma
• age 21-90 years

Exclusion Criteria:

• inability to give informed consent
• current ocular infection
• more than 1 prior trabeculectomy, or more than 1 prior tube shunt
• previous refractive surgery
• pregnant women
• heart failure
• renal failure or uncontrolled urine retention
• corneal abnormalities preventing reliable IOP measurement

All participants will have open angle glaucoma and have undergone either tube shunt surgery or trabeculectomy. All participants will be matched for range of recent intraocular pressure (average over the prior three visits of <12 mm Hg, 12 to <18 mm Hg, or >18 mm Hg), as well as number of medications (none, 1-2, 3 or more).

A manuscript is currently under development.