Glaucoma drainage devices (GDD)/drainage implants/aqueous shunts/tube shunts are small devices placed on the eye to treat glaucoma.
When glaucoma occurs, the aqueous humor cannot drain properly through the front of the eye, resulting in increased intraocular pressure and damage to the optic nerve head as well as the retinal nerve fibers at the back. If left untreated, glaucoma can lead to permanent blindness.
The drainage device creates a new drainage pathway for the eye through the device’s tube, helping to reduce intraocular pressure. After surgery, the device is positioned on the sclera, attached and curved along the eyeball with conjunctiva covering it, and the tube’s tip is placed in the anterior chamber without interfering with vision.
When to perform glaucoma surgery with drainage device implantation
Generally, tube drainage devices are used in cases where previous trabeculectomy surgery (creating a filtration bleb on the eye surface) has failed and cannot control intraocular pressure to a safe or target level.
However, this method may be used as the first-line surgery for certain types of glaucoma without creating a filtration bleb, such as neovascular glaucoma and uveitic glaucoma.
Tube drainage device implantation surgery for glaucoma
This surgery can be performed on an outpatient basis using local anesthesia and takes about one hour. General anesthesia is reserved for special cases, such as patients who cannot communicate, have hearing impairment, claustrophobia, or altered mental status.
Types of tube drainage devices for glaucoma
- Non-valved GDD, such as ClearPath implant, Baerveldt implant, Molteno implant
- Valved GDD, such as Ahmed implant
Each type of tube device is made from specific materials and techniques. Additionally, each type is subdivided into various sizes. The choice of device depends on the suitability and the surgeon’s consideration. In cases where patients cannot consistently use eye drops after surgery or have difficulty attending follow-up appointments, the surgeon may prefer to use a valved tube device first.
Risks and complications after glaucoma surgery with tube drainage device implantation
As with other surgeries, tube drainage device implantation carries risks and potential postoperative complications.
In the early postoperative period, complications similar to trabeculectomy may occur, such as flat anterior chamber, hypotony (low intraocular pressure), and suprachoroidal hemorrhage.
Other possible complications include intraocular bleeding, eye infection, scarring on the eye surface, malfunction or poor function of the device valve, cataract formation, double vision, strabismus, vision loss, and the need for repeat surgery to correct issues. Additional glaucoma surgeries may be required, such as removing the old device or implanting a new drainage device.
Preoperative and postoperative care for glaucoma surgery with drainage device implantation
Before surgery, patients with underlying conditions who take blood thinners or have anemia should inform their doctor to prevent possible complications. Eye drops and/or oral glaucoma medications should be used as usual until the day of surgery.
After surgery, glaucoma medications will be stopped. Patients will receive eye drops and ointments to reduce inflammation and prevent infection, which will be used continuously for several weeks and then gradually tapered off.
Some patients may experience temporary elevated intraocular pressure within 1-6 weeks after surgery. The doctor will prescribe eye drops to lower the pressure. Once the drainage device functions properly and intraocular pressure decreases, the doctor will consider stopping the pressure-lowering medications.
Even if the surgery is successful, postoperative follow-up remains important and affects long-term surgical outcomes. Patients should use medications as prescribed, follow medical advice, and attend scheduled appointments regularly. If any abnormalities occur in the operated eye, such as redness, severe pain, discharge, or decreased vision, patients should inform their doctor immediately as these may be early signs of infection.
