New implant for drainage in glaucoma. Clinical trial.

Abstract

The implant described in this communication is the direct descendent of a long series of artificial drainage devices which began when Zorab (I9I2) inserted a silk thread through the limbus in order to drain aqueous into the subconjunctival space in cases of glaucoma (see also Mayou, I9I2). Among the more recently described devices are teflon drainage tubes in man (Richards, I955; Epstein, 1959; Ellis, I960) and gel film strips in rabbits (Laval, I955; Barsky and Schimek, I958). While short-term results with these implants have been promising, long-term results have been uniformly disappointing. The translimbal tubes of Ellis and Epstein have certainly maintained a patent fistula yet drainage has ceased. This failure of drainage has been ascribed to fibrosis in the bleb wall, the fibrosis itself being caused by a hypothetical action of the draining aqueous on the tissues (Stanworth, 1958; Tribin-Piedrahita, I965). To prevent any reduction in area of the bleb by fibrosis, an implant has been designed consisting of a translimbal tube rigidly attached to and opening onto the external surface of a thin acrylic plate. This plate, curved to fit the sclera lies under the conjunctival and episcleral tissues. The tube guarantees patency of the fistula while the plate, sutured to the sclera, forms the floor of a bleb which cannot shrink to an area less than that of the plate. In order to develop a mechanically satisfactory implant experimental work has been carried out on rabbits.