A New Adjustable Glaucoma Drainage Device

PURPOSE. This work is focused on the testing of a new experimental noninvasively adjustable glaucoma drainage device (AGDD) that allows for the control of its outflow resistance to modulate intraocular pressure (IOP) in a customized fashion. METHODS. Six AGDDs were directly connected to a pressure transducer and a perfusion system continuously delivering saline solution at rate of 2 mu L/min. The steady-state pressure was measured and reported as a function of the angular position of the AGDD disk. Ex vivo experiments were conducted on six freshly enucleated rabbit eyes. The IOP was measured, and the flow rate was increased with a syringe pump to simulate elevated IOP associated with glaucoma. After insertion of the implant in the anterior chamber, the position of the disk was sequentially adjusted. RESULTS. The relation between the pressure drop and the angular position of the AGDD disk is nonlinear. The functional range lies between 80 degrees and 130 degrees, which allows for four or five different reproducible adjustment positions. Above 130 degrees the implant is considered to be closed (no outflow), and below 80 degrees it is considered to be open (minimum resistance to flow). CONCLUSIONS. The resistance to outflow of the experimental AGDD can be adjusted to keep IOP in the desired physiological range. This feature could be useful for addressing the risk of hypotony in the early postoperative stages and could provide a means to achieve optimal IOP under a wide range of postoperative conditions.