When treatment with eye drops, pills, laser or prior glaucoma surgery does not lower intraocular pressure to a safe level, your ophthalmologist may determine that glaucoma drainage device surgery may be performed. In some patients, particularly those who have had prior eye surgeries involving the conjunctiva, those with certain types of glaucoma such as aphakic glaucoma, neovascular glaucoma, and uveitic glaucoma are known to be good candidates for tube shunts. It should be noted that the glaucoma implant is not used to improve vision, but rather to lower intraocular pressure and prevent further vision loss from glaucoma. It has no relation to the implants used in cataract surgery.
Glaucoma drainage implants come in different shapes and sizes and all have a tube and plate. The most common type implanted at the Glaucoma Center of Michigan is the Baerveldt Implant. However, regardless of which type of implant is used, a silicone tube is inserted into the front of the eye, usually between the cornea and iris, but other locations are occasionally used. The tube acts like an artificial drain, allowing fluid to pass through it to a plate, which has been placed on the surface of the eye and acts as a reservoir. The fluid then slowly percolates through this reservoir and is absorbed into the body fluids. The implant plate is usually placed in the area underneath the upper eyelid and is not visible unless the lid is pulled back. With the upper lid retracted, a clear or white patch may be noted. This is a patch that covers the tube and prevents irritation.
This is an outpatient procedure performed in an ambulatory surgery center. The surgery is usually done under local anesthesia with IV sedation and usually with a special eye nerve block. Your doctor will want to examine you in the office the following day and you will be prescribed a regimen of postoperative drops. Immediately after the surgery, intraocular pressure may not be lower and depending on how surgery is performed, glaucoma medications may be continued during this period. For several weeks following the surgery, your ophthalmologist will observe your eye closely and examine you frequently.
The tube usually opens and begins to drain fully about 6 weeks after surgery. When this happens, the eye pressure may drop suddenly and you may experience blurry vision, an ache around the eye and/or light sensitivity. This is a common occurrence and if this happens, please contact our office with any questions. In general, it commonly takes several months after your surgery for the healing to be complete and for the implant to mature in your eye. During this time, it is not unusual for your intraocular pressure, as well as your vision, to fluctuate. You will be ready to change your glasses prescription, if needed, approximately 2-3 months after surgery.