A randomized double-blind study of aqueous humor flow and intraocular pressure measurements before and four hours after instillation of placebo and beta-blocker eyedrops, was carried out in 40 hypertensive patients. The treated and non-treated patients either did or didn't show an optic disc excavation and a visual field defect. Hypertensive patients with a previous tension treatment will stop therapy on a 3-week period up to an increase of their own ocular tension value greater than or equal to 3 mmHg. The intraocular pressure statistically decreased of 20.8% four hours after topical placebo, the aqueous humor flow remaining unchanged. In this study, timolol eyedrops induced a greater decrease of the aqueous humor flow (39%), followed equally by betaxolol (23.8%) and carteolol (20.42%). Timolol and betaxolol eyedrops equally induced a significant decrease of the intraocular pressure. There was no effect of carteolol on the intraocular pressure. The outflow facility was independent of the instilled beta-blocker eyedrop.