Diurnal variation of intraocular pressure in primary open-angle glaucoma.

Intraocular pressure was measured with a Goldmann applanation tonometer in 12 normal individuals (24 eyes), 14 ocular hypertensives (28 eyes), and 14 patients (27 eyes) with primary open-angle glaucoma every hour for 24 hours. In most subjects, pressure was highest sometime during the day and pressure elevation before rising was not demonstrated. The lowest intraocular pressure was most frequently observed early in the morning, whether the patient was normotensive or hypertensive. Fourteen of 27 glaucomatous eyes had intraocular pressure below 20 mm Hg early in the morning.