A glaucoma drainage tube or “shunt” is a specialized glaucoma drainage device that allows fluid from inside the eye to bypass the eye’s own drainage pathway to lower eye pressure. A glaucoma tube shunt has two main parts. A silicone tube which usually is implanted in the front compartment of the eye (anterior chamber) and a “plate” which is usually implanted between or under the eye muscles.
When a glaucoma drainage tube is implanted, internal eye fluid or aqueous humor flows through the tube and drains into a capsule or pocket that forms over the plate of the glaucoma implant. Drainage of internal eye fluid through this tube will lower eye pressure.
Glaucoma tube surgery only lowers eye pressure. It will not make you see better and cannot reverse existing damage to the optic nerve. However, lowering eye pressure to a desired level or range will help lower the risk of further glaucoma damage to the optic nerve and therefore lowers the risk of progressive loss of vision or blindness due to glaucoma.
What is the success of glaucoma tube shunt surgery?
On the average, after 1 year 90%, and after 3 years 60% of operated eyes achieve significantly improved eye pressure control after glaucoma drainage tube implantation with or without the need for medication (eye drops). A comparative trial evaluating the success between different types of glaucoma drainage tubes is underway. Currently, your doctor, on an individual basis will determine the type of glaucoma drainage tube that will be selected. However, since many patients who require glaucoma drainage tubes for eye pressure control often have other complicated eye problems (such as advanced diabetic eye disease or poor circulation due to blockage of blood vessels inside the eye) the overall health of the eye will also depend upon successful management of the other problems affecting the eye in addition to glaucoma. Even after successful control of eye pressure some patients experience a continued loss of vision due to worsening of the other co-existing problems in the eye like diabetes or poor eye circulation.
Will I still need glaucoma drops after drainage tube surgery?
Most patients who have successful implantation of a glaucoma drainage tube will require significantly fewer glaucoma medications to maintain eye pressure in a desirable range. Some patients may be successfully weaned off all glaucoma medications.
Will I be able to see the tube after surgery?
The tube itself in most cases is not visible inside the eye to the casual observer. A square or rectangular patch graft made of processed human tissue is usually placed over the tube to protect the tube from extruding or eroding through the eye. This patch graft is usually visible as a whitish square or rectangle when the upper or lower lid is pulled away from the eye.
Will I feel the drainage tube after surgery?
A sandy or gritty feeling after surgery is normal and this is usually due to the stitches on the surface of the eye. This sensation will usually disappear when the stitches dissolve after several weeks. Tenderness of the eye to touch is common after any invasive eye surgery and is not usually caused by the presence of the tube shunt itself. The discomfort usually fades and disappears when the eye is completely healed.
What are the complications and risks of glaucoma drainage tube surgery?
Although most patients will benefit from improved eye pressure control after drainage tube surgery, as with all surgical procedures there are potential risks in addition to benefits. Most problems following surgery can be successfully treated in the office. However, occasionally, additional surgery may be necessary for persistent post-operative problems or new problems that may develop later. Mild visual loss that is not reversible occurs on the average in about 5% of patients and severe visual loss including total and irreversible visual loss as a result of a tube shunt related complication occurs in less than 1% of operated eyes. However, depending upon the cause of the glaucoma, some patients will continue to suffer a decline in vision even after successful glaucoma drainage tube surgery. This is usually due to the presence of a co-existing eye disease that caused the glaucoma such as for example; advanced diabetic eye disease. Therefore, the health and survival of the eye in some patients is not related to the outcome of glaucoma drainage tube surgery.
Complications that may occur during or following glaucoma drainage tube surgery include but are not limited to; infection, choroidal hemorrhage (sudden bleeding behind the retina), choroidal effusion (fluid accumulation behind the retina), macular edema (swelling in the central part of the retina), low eye pressure, corneal swelling, bleeding in the front compartment of the eye, chronic inflammation, erosion of the tube or drainage plate, double vision, tube migration or malposition, cataract development or worsening of an existing cataract, chronic inflammation, chronic eye discomfort, blind painful eye, and droopy lid.
- Glaucoma medications need to be instilled in the eye up to the morning of glaucoma surgery. Patients who are taking glaucoma pills (diamox/acetazolamide or neptazane/methazolamide), unless instructed otherwise should take the morning dose with a small sip of water.
- Scrub lashes with baby shampoo mixed with water (1 part shampoo 3 parts water) using a cotton swab and then rinse with warm water beginning 5 days prior to surgery. Alternatively, an over the counter eyewash such may be used instead of baby shampoo. Your doctor may suggest different eyewash brands.
- You may need antibiotics pills, drops, or ointment before surgery. You doctor will advise you if these are necessary.
- Food and drink are permitted only until midnight the day before surgery. Afterwards you must not eat or drink anything except for your heart and blood pressure medications. They should be taken the morning of surgery with a small sip of water. If you are taking blood thinners such as aspirin, plavix, or coumadin only your family physician or cardiologist can tell you if it is safe to stop them prior to surgery. Your family physician will instruct you regarding the use of your non-eye medications prior to surgery.
Post-Operative Instructions and Expectations
Expect to be seen the first day after surgery and on the average weekly for the first month. Close follow-up is extremely important in order to observe and control the healing response and increase the likelihood of surgical success.
A separate handout with detailed post-operative instructions will be given to you at the time of surgery.