A prospective study of 161 consecutive glaucoma patients conducted from June 1983 to May 1984 showed that 81 (50.3%) had unilateral glaucoma. The causes of the unilateral disease were primary open-angle glaucoma (38.3%) and secondary glaucoma (61.7%). During this year long study primary angle-closure glaucoma was not observed. The relatively frequent occurrence of unilateral primary open-angle glaucoma poses a riddle for which I have no explanation to offer.
