We have reviously described surgical techni ues for draining severe cases of secondary glaucoma by means of% artificial implant Wherever posshe these implants have been inserted in two stagesThe modern microsurgical operation of trabeculectomy gives excellent results in selected cases of primary glaucoma. However, where glaucoma develops in young patients or is associated with trauma, aphakia, chronic uveitis, anterior segment neovascularisation or failure of a previous drainage operation, results are generally poor. In the latter group, we use a draining implant consisting of a thin silicone tube connected to drain on to the upper surface of one or two rigid circular episcleral plates. These implants are placed with the silicone tube lying in the angle of the anterior chamber and the plate or plates firmly sutured to the sclera and covered by a thick flap of Tenon's tissue and conjunctiva.The aqueous that is drained by these implants passes through the tube to enter a cleft between the episcleral plate and the overlying tissues. From this cavity it escapes freely in the first seven to ten days after operation. During this time the intraocular pressure (IOP) is very low, ranging between 0 and 5 mmHg. This period of hypotension ceases when the tissue reaction to the presence of the implant and to the aqueous