Tube shunt surgery is a surgical procedure done to manage glaucoma. Glaucoma is an eye condition caused by higher than normal intraocular pressure (IOP). Elevated IOP arises when there is a blockage within one of the eye's passages, causing the accumulation of aqueous humour.
The tube shunt device is a flexible, plastic tube attached to a plate (which acts as a drainage pouch), and is put under the conjunctiva. The aqueous humor is diverted and moves through the tube to the plate's end, where it is collected and drained through the eye's natural drainage system. This results in lower IOP, thus helping control glaucoma.
This procedure has been proven to help manage several types of glaucoma, such as neovascular glaucoma, traumatic glaucoma, and pediatric glaucoma. The surgery does not assist with regaining lost vision. It only helps to stop or slow down vision loss. The surgery can also help the patient to stop or reduce the amount of glaucoma eye drops they are using.
Tube shunt surgery is easily comparable to trabeculectomy as they both result in better drainage of aqueous humor. Even though trabeculectomy is seen as more effective than tube shunt surgery, it has greater risks. Tube shunt surgery results in less severe scarring, which can block the drainage opening.
The surgery is not usually used as the first treatment option for glaucoma. It is often used when patients have previously undergone failed trabeculectomy or laser surgeries. It is also a good option when the patient has experienced trauma that caused conjunctival scarring. If the patient is likely to form scar tissue, tube shunt surgery may be performed first.
Also Known As
- Trabecular tube shunt
- Glaucoma tube shunt surgery
There are two types of shunts that the surgeon may opt to use:
- Ahmed valve - The full effects can be seen immediately
- Baerveldt shunt - The full effects are seen after 4 -6 weeks
Before the Procedure
The eye specialist will give the patient instructions to follow before the day of the procedure.
The patient is typically allowed to leave after the procedure. Since sedation is used, patients are advised not to drive themselves home. In some unique instances, such as with children, they may have to stay at the hospital overnight.
The surgeon begins the procedure by administering anesthesia. Usually, local anesthesia is used, however, if the patient is anxious or a child, it is done under general anesthesia. Sometimes pain medication is administered intravenously to some children during the surgery. After the eye is numbed, it is cleaned and a sterile drape is placed over the face, only exposing the eye. Retractors are used to hold the eye in place.
The surgeon then makes an incision on the conjunctiva. An implant plate is put under the conjunctiva and attached to the white of the eye (sclera). This is done while avoiding causing damage to the recti muscles.
The tube can either be placed in the anterior or posterior chamber. When inserted into the posterior chamber, the vitreous is entirely or partially removed. If placed in the anterior, that part of the eye is drained of excess fluid. Where the cornea and sclera meet, a needle puncture is made. The tube passes through this hole and enters either the anterior or posterior chamber.
After the tube has been inserted, the hole is sealed with an autologous scleral patch. If the surgeon has implanted a free-flow implant, the tubing is tied with a disposable suture or the ligature is put in a position that allows the surgeon to remove it easily after a few weeks.
The surgeon injects antibiotics into the conjunctiva and tapes the eye shut. S/he then places a clear plastic eye shield or patch over the eye.
Risks & Complications
Although the surgery is considered considerably safe, it is still associated with some risks and complications, even with the best surgical practices. It shares similar pre and post-operative experiences as trabeculectomy.
After surgery, the eyes may also be sore and have a gritty and burning sensation. These side effects are mild and last for a maximum of 2 days. The patient's vision may worsen. However, this improves in two weeks.
Some complications include:
- Infection - Although the patient is required to use antibiotics after the surgery, there is a rare chance that the eye may still be infected. Lack of immediate attention can lead to vision loss. Sometimes, an infection may require removal of the shunt.
- Surgery failure - As time passes, the eye starts to heal and slowly rejects the shunt as it is a foreign object. This means that the patient has to resume their glaucoma medication or undergo further operation.
- Choroidal detachment
- Double vision
- Movement the tube
- Eye muscle imbalance
- Droopy eyelid
If the patient experiences sudden and severe pain or vision loss, they should immediately seek medical attention.
Aftercare & Recovery
After surgery, the patient will be required to use a corticosteroid medicine to help control inflammation, and antibiotics to lower the risk of infection for several weeks postoperatively. If the patient experiences any constipation, they will be given laxatives to avoid straining their eye while trying to pass stool. Straining the eye can cause increased pressure in the eye. The patient may also be required to keep using their glaucoma medicine due to possible spikes in the IOP.
A plastic shield should be worn for a week. It should also be worn when the patient is sleeping to avoid unintentionally rubbing the eye. When outside during the day, sunglasses should be worn. The patient will also be required to avoid any activities that can cause the eye to jar. These activities include bending, running and lifting items more than 5 kilograms. They can use screens as usual, although they'll find that their eyes tire easily. The patient can resume work after a few days.
The patient sees the doctor a day after the surgery, once a week during the first month, twice during the second month and once during the third month. Depending on how the eye heals, more or fewer visits may be required. During the follow-ups, the specialist monitors for signs of hypotony/dangerously low intraocular pressure and ensures the chamber has not shallowed too much.
After about two weeks of the tube placement, the IOP significantly lowers. In two months, the pressure should stabilize at between 16-18 mm/hg.
About 50% of tube shunt surgeries are successful. However, when it fails, the surgeon may opt to implant a second tube or perform a cyclodestructive laser procedure.