A Baerveldt shunt is a medical device used in ophthalmology, specifically designed to manage glaucoma. It functions as a type of glaucoma drainage device, also known as an “aqueous shunt,” that lowers the elevated pressure inside the eye. This small implant consists of two main components: a thin silicone tube and a flat plate. The tube directs fluid, while the plate acts as a collection area for this drained fluid.
Purpose of a Baerveldt Shunt
Glaucoma is an eye disease characterized by high intraocular pressure (IOP), which can damage the optic nerve and potentially lead to vision loss. The eye constantly produces a fluid called aqueous humor, which normally drains through a natural system. When this drainage pathway is blocked or not functioning properly, fluid builds up, causing pressure to rise within the eye. A Baerveldt shunt is considered when other treatments, such as eye drops, laser therapy, or other surgical procedures, have not successfully reduced this elevated eye pressure.
The function of a Baerveldt shunt is to create an alternative pathway for the aqueous humor to drain from the eye. The silicone tube is placed inside the eye, allowing fluid to flow out to the plate, positioned on the outer surface of the eye, usually hidden under the eyelid. This fluid then collects in a small fibrous capsule, often called a bleb, where it is absorbed by surrounding tissues and blood vessels, thereby reducing the intraocular pressure. Baerveldt shunts are used for complex forms of glaucoma, including neovascular glaucoma, uveitic glaucoma, or when previous glaucoma surgeries have not achieved adequate pressure control.
The Surgical Implantation Procedure
Implanting a Baerveldt shunt is an outpatient surgical procedure performed under local anesthesia for patient comfort. The surgeon begins by making a small incision in the conjunctiva, the clear membrane covering the white part of the eye, to access the underlying sclera. The flat plate of the shunt is then positioned on the surface of the eye, often anchored with sutures to the sclera beneath the eye muscles.
Once the plate is secured, the tiny silicone tube is inserted into the front chamber of the eye. To prevent the eye pressure from dropping too low immediately after surgery, a dissolvable stitch, often called a Supramid stent stitch, is placed either through or around the tube to temporarily restrict fluid flow. A tissue patch graft, such as donor sclera or pericardium, is used to cover the portion of the tube resting on the sclera, protecting it from exposure. The conjunctival incision is then closed with sutures.
Recovery and Postoperative Care
Following Baerveldt shunt surgery, patients wear an eye shield or patch for the immediate post-operative period, often for the first night. Patients may experience some redness, swelling, and a gritty sensation in the eye, and the eyelid may droop temporarily, which resolves within a few weeks to months. Strict adherence to a regimen of prescribed eye drops, consisting of antibiotics and anti-inflammatory steroids, is necessary to prevent infection and control inflammation; these are used multiple times daily for several weeks.
Patients are advised to avoid activities that could increase eye pressure, such as bending over, heavy lifting, or strenuous exercise. Activities like swimming and contact sports should be avoided for a period. Regular follow-up appointments, often weekly for the first month, are scheduled to monitor eye pressure and overall healing. A temporary spike in eye pressure can occur a few weeks after surgery as the dissolvable stitch releases and the shunt begins to function fully, a phase that ophthalmologists closely manage with medication if needed.
Potential Complications
While Baerveldt shunt surgery is successful in controlling eye pressure, complications can arise. One concern is hypotony, where the eye pressure drops too low (below approximately 5 mmHg), which can compromise vision. Conversely, a pressure spike, or hypertension, can occur, particularly before the temporary stitch releases and the shunt fully engages. Both low and high pressure require monitoring and management by the ophthalmologist.
Other issues include infection, which, though rare, can be serious. Double vision, known as diplopia, may occur due to the implant’s placement beneath eye muscles, although lower incidences are reported. Mechanical problems are possible, such as the tube becoming blocked by scar tissue or migrating from its intended position within the eye. While these complications can occur, ophthalmologists monitor for them during follow-up visits for timely intervention if needed.