Relationship between postural change of the intraocular pressure and visual field loss in primary open-angle glaucoma

To determine the relationship between the postural changes of the intraocular pressure and the visual field loss in patients with primary open-angle glaucoma.

Eleven normal subjects and 11 patients with primary open-angle glaucoma were studied. Intraocular pressure was measured in both the sitting and the supine positions. Visual fields were measured with automated perimetry.

When patients moved from a sitting to supine position, the intraocular pressure increased by an average of 3.1 +/- 0.4 mm Hg (mean +/- SEM) in normal subjects and 4.0 +/- 0.2 mm Hg in patients with primary open-angle glaucoma. There was a significant difference between the normal subjects and patients with primary open-angle glaucoma (P = 0.049). Intraocular pressure increased by 4.4 +/- 0.3 mm Hg (P = 0.02) in the worse eye for mean deviation and 3.6 +/- 0.3 mm Hg (P = 0.38) in the better eye for mean deviation. There was no significant difference in intraocular pressure in the sitting position between both groups.

The greatest difference in intraocular pressure between the sitting and supine positions was observed in the worse eye of patients with primary open-angle glaucoma. This result suggests that damage to the optic nerve in primary open-angle glaucoma might occur when patients are asleep in the supine position.