The first type of surgery for glaucoma that is attempted is trabeculectomy. When trabeculectomy surgery is not successful and your glaucoma worsens, the next step is to implant a drainage device or shunt.
Glaucoma Drainage DevicesGlaucoma drainage devices (GDDs) are tiny tubes made of silicone or polypropylene. These tubes are attached to a plate that is then attached to the surface of your eye. The plate is held in place by donor tissue or your own tissue. The tube allows an escape route for fluid to exit the eye, reducing the intraocular eye pressure to a safe level where no more progression of glaucoma occurs.
Some glaucoma drainage devices contain a valve. These devices are set so that a certain pressure is required before the valve opens and fluid is allowed to flow. When using devices with no valve, your surgeon will place a dissolvable suture. As the suture dissolves over about six weeks, scar tissue will form that will prevent too much fluid from leaving the eye.
Care After Placement of Glaucoma Drainage DevicesAfter receiving a GDD, you will probably be treated with topical antibiotic and steroid eye drops. Your doctor may also prescribe a cycloplegic eye drop to keep you more comfortable and also to keep the anterior chamber (the front part of your eye) well formed. Depending on the type of implant used, you may or may not be asked to continue using your topical glaucoma medications. You will be asked to avoid strenuous activity, heavy lifting and bending over. You will also be given a protective shield to wear while sleeping.
Complications of Drainage DevicesThe following complications may occur after receiving a glaucoma drainage device to control eye pressure:
- Hypotony: Hypotony is a condition in which the eye pressure may actually be too low. Low eye pressure is unhealthy for the eye and can cause choriodal effusion or retinal detachment.
- Tube obstruction: Occasionally, fibers or blood can plug up the tube, preventing proper outflow. Surgeons can correct this by injecting a certain chemical to dissolve obstructions.
- Double vision: Because drainage devices are implanted close to the eye muscles, double vision can be a complication. Surgeons can sometimes manipulate the implant through massage or other procedures to minimize double vision. In some cases, the device must be removed. Double vision occurs because there may not be enough room for the eye muscles to move and contract properly because the device gets in the way. The eye muscles may be unable to fuse the image seen with each eye.
Success Rate of Drainage DevicesThe success rate of glaucoma drainage devices is 75% after one to two years, depending on the type of device implant. Some people may still receive the benefits of lower eye pressure, but not enough to discontinue topical or oral glaucoma medications.
Kwon, Young, John H Fingert, and Emily C Greenlee. A Patient's Guide to Glaucoma. Illustrated and copy edited by Trish Duffel, RPh, MA, The University of Iowa, April 2008.