Little is known about the relation between diurnal variations of intraocular pressure (IOP) and prognosis for glaucomatous visual field damage. The association between apparent progressive loss of visual field and the occurrence of IOP peaks was studied. Pressure peaks were detected by a self-tonometer in the natural environment of patients with glaucoma. The study groups consisted of patients with and without a strong indication of progressive visual field losses, all with IOPs of 22 mm Hg or less obtained in the ophthalmologist's office. Patients apparently undergoing progressive visual field loss were found to have significantly more frequent IOP peaks than patients with stable visual fields. A statistical evaluation indicated that, in a population with a 30% prevalence of progressive loss of visual field, 75% of the patients with peaks have progressive loss and 75% of those without peaks do not have visual field progression. Intraocular pressure peaks were thus shown to have an association with the apparent progression of vision loss independent of the mean IOP. Home tonometry appeared to be a promising tool for identifying patients at increased risk of developing visual field loss who may require intensified follow-up and an alteration in clinical management. However, the present study must be complemented by a prospective study.