• Factors affecting the progression of visual field loss were examined in 57 patients with bilateral open angle glaucoma. Patients who already had marked visual field loss experienced further field loss at a greatly accelerated rate. Family history of glaucoma, sex, and initial registration intraocular pressure were also important prognostic factors for progressive visual field loss, whereas age and systemic blood pressure were not found to affect rate of visual field loss. Followup data from these patients were drawn from a computer-based clinic record system that may serve as a prototype for the collection of information on the natural history of ophthalmic diseases.