Glaucoma is a condition in which fluid in the eye, also known as the aqueous humor, accumulates, which causes a gradual increase in eye pressure. This increased pressure can lead to nerve damage, resulting in loss of vision. Glaucoma is treated using medications or surgery which attempt to lower the pressure in the eye. Sometimes small shunts are implanted to drain the aqueous humor.
Purpose
Glaucoma can often be treated by making small holes that can allow excess fluid to drain out of the eye, a procedure which is known as a trabeculectomy. These surgically-created holes may need a small device, known as a shunt, which can be placed in the opening to help with the drainage. These devices also will keep the drainage holes from closing or healing over. Most of these implanted shunts, according to the Glaucoma Research Foundation, are tubes that are hollow in the middle, which allows the aqueous humor to drain through the shunt. Some shunts have valves that can help control the flow of liquid.
Indications
Glaucoma shunts are typically used for cases of glaucoma that are considered to be "complicated," the Massachusetts Eye and Ear Infirmary explains. Complicated glaucoma does not respond well to medications or laser surgery. The use of tube shunts may be necessary if a previous trabeculectomy has failed, or in certain types of glaucoma where traditional trabeculectomy surgery would almost certainly fail, which can occur in patients who have had corneal transplants or who have a type of glaucoma known as neovascular glaucoma.
Procedure
Tube shunts for glaucoma are installed into the top of the eye. The device sits underneath the outer covering of the eye, also known as the conjunctiva, which also helps conceal the device. Eye shunts are installed in an operating room under local anesthesia. The eye is be treated with some eye drops to facilitate the procedure and the eyelids themselves are held open with a device called a speculum to prevent blinking. After the procedure, the patient needs to wear a patch over the treated eye, which is removed the day after the procedure during the first post-operative visit.
Risks
There are a few risks associated with installing a tube shunt for glaucoma, All About Vision notes. Sometimes, the shunt can lower the pressure in the eye too much, which causes a condition known as hypotonia. The shunt can also be placed too close to the surface of the eye, which can cause the cornea to erode. Sometimes, the shunts can also wear down the surrounding tissue of the eye, which can also cause tissue damage.
Benefits
The goal of installing a tube shunt, the Massachusetts Eye and Ear Infirmary explains, is to slow or halt the progression of glaucoma, preventing additional loss of vision. Any vision that has already been lost does not return. Patients also need to continue utilizing any eye drops or other medications for their glaucoma until they have been told by their physician that they no longer need to use them. This surgery can, however, be very effective at treating glaucoma for patients who have not had their condition controlled by other approaches.
