Glaucoma valve Glaucoma valve A glaucoma valve is a medical shunt used in the treatment of glaucoma to reduce the eye's intraocular pressure (IOP). The device works by bypassing the trabecular meshwork and redirecting the outflow of aqueous humour through a small tube into an outlet chamber or bleb. The IOP generally decreases from around 33 to 10 mmHg by removing aqueous on average 2.75 microliters/min. Professor Anthony Molteno developed the first glaucoma drainage implant, in Cape Town in 1966. Following on the success of the Molteno implant, several varieties of device have been developed from the original, the Baerveldt tube shunt,
Glaucoma valve drainage, such as iStent, CyPass, or Hydrus. A Cochrane Review of various aqueous shunts and modifications found that the Baerveldt implant may result in lower IOP than the Ahmed implant, but it was unclear if the difference in IOP reduction was clinically significant. The review suggests that practitioners should operate with the devices that they are most comfortable with, and have the most experience using. The glaucoma valve implant is indicated for glaucoma patients not responding to maximal medical therapy, with previous failed guarded filtering surgery (trabeculectomy) or in cases where conventional drainage surgery is unlikely to succeed. Common situations