Glaucoma is caused by the build-up of fluid in the eye (called aqueous humour, or just aqueous). This causes pressure in the eye (called intraocular pressure or IOP) to increase, which damages the optic nerve and leads to vision loss. An aqueous shunt is a device which is implanted into the eye and improves the drainage of the fluid out of the eye. This page describes how the shunt works to treat glaucoma and the surgery involved.
An aqueous shunt is a device which drains aqueous humour out of the eye to a small blister (called a bleb) under the surface of the eye (the conjunctiva). It bypasses the normal drainage channels in the eye, and drainage of the aqueous out of the eye is improved, reducing IOP.
Different types of shunt are available. The two most common types are the Ahmed Glaucoma Valve or the Baerveldt Glaucoma Implant. Other common names for this type of device are tube implant, glaucoma drainage implant or glaucoma tube shunts.
The shunt has two parts: a small silicon tube and a plate. The aqueous drains down the tube to the plate, which sits in the conjunctiva.
By improving the flow of aqueous out of the eye, the IOP will decrease. This reduces pressure on the optic nerve, which means vision loss is less likely. However, any vision already lost to glaucoma can’t be recovered, and the glaucoma is not cured.
This type of treatment is for people with moderate to advanced glaucoma, particularly where eye drops aren’t working very well.
The surgery is usually done under local anaesthetic, which means you will be awake but the eye will be numb. It usually lasts one to two hours, and you will probably be able to go home the same day or the next day.
The shunt will not normally be permanently visible after surgery. While the eye is healing from the surgery, it will probably be red and swollen.
You will be seen by your ophthalmologist the day after the surgery, and will be given antibiotic and steroid eye drops to improve recovery. You must continue to take all eye drops as directed, including for your other eye if you have glaucoma in both eyes. You’ll be asked to attend several follow-up appointments after the surgery to check the eye is healing well and the device is working. It is very important to attend all these appointments.
It will take your eye several weeks to recover from the surgery, so you’ll need to take some time off work and avoid some types of physical activity.
Aqueous shunt surgery is a safe procedure, although as with all operations there is some risk, for example of infection. For most people with glaucoma, the surgery reduces IOP well. This means fewer eye drops and a better chance of protecting vision.
If you would like to know more about aqueous shunts, download or order our free information leaflet.