Mass screening of the optic disc for glaucoma: a follow-up study.

Because of the high false positive and negative rates for detection of suspects when screening for glaucoma by tonometry, we screened 12 156 subjects over the age of 40 years or with a stated family history of glaucoma by examining the optic discs. This was followed by Schiotz tonometry. Eight hundred and twelve (6.7%) suspects were referred to their primary physician for investigation by an ophthalmologists. A database program was used to send out follow-up letters to both suspects and ophthalmologists. Three hundred and seventy-nine replies were received from ophthalmologists: 100 (26.4%) of these suspects had ocular hypertension and 68 (17.9%) had glaucoma. Of these 68, 60 (15.8%) had chronic simple glaucoma, five (1.3%) had secondary open-angle glaucoma, and three (0.79%) had primary closed-angle glaucoma. The prevalence of all types of glaucoma in this group for which follow-up was obtained was at least 0.56% of the total number screened. Assuming that the prevalence was similar for the group for whom no replies were obtained, the prevalence of glaucoma in this population is approximately 1.19%. Screening by optic disc examination is therefore likely to detect most cases of glaucoma.