Figure 1  .

(A) Single plate Molteno implant (scale bar = 1 cm). (B) Dual chamber double plate Molteno implant (scale bar = 1 cm). (C) Schematic drawing of the resistance mechanism of a dual chamber single plate Molteno implant. The thin V-shaped ridge (see B) has the same height as the circumferential rim of the polypropylene plate. The top surface of the plate is divided into one smaller and one larger chamber by the apposition of the overlying conjunctival and Tenon's layers (dotted line). Aqueous flows (black arrow) into the smaller proximal chamber until sufficient pressure is achieved within the chamber to lift (white arrow) the overlying conjunctival layer to allow free drainage.