In one prospective study, 75 eyes (47 children with congenital glaucoma) were treated by trabeculotomy. Intraocular pressures were controlled in 93.4% after one or more trabeculotomy operations. In five eyes the intraocular pressure was not controlled and these had a fibrovascular membrane in the angle, extending over the trabeculum and iris base with finger-like processes over the peripheral iris. The eyes that had successful operations did not have this appearance. In a second study trabeculotomy in adult-onset open-angle glaucoma had a high rate of failure (30%) including the use of postoperative medication. Nineteen eyes (17 patients) were operated on, 13 successfully. Another group of 19 eyes (17 patients) were treated by trabeculectomy, with the same follow-up period. The one failure (5%) occurred in an eye in which the angle appeared to be totally closed on gonioscopic examination. The operation was equally effective in black and white patients.