Glaucoma is a chronic eye disease with raised intraocular pressure (on most occasions) and is potentially blinding if left untreated or if treatment is delayed. Glaucoma could be managed by various means, including eye drops, tablets, lasers and various drainage surgeries. This information is designed to help you not only to decide about this surgery but also make you aware what to expect.

 Who would benefit from a glaucoma tube shunt implant?

Glaucoma tube-shunt implant surgery is a complex glaucoma procedure that is normally reserved for patients with complex secondary glaucoma, advanced glaucoma and refractory glaucoma with uncontrolled eye pressures even on maximum glaucoma medications. This is also indicated when conventionalglaucoma filtration surgery (trabeculectomy) is unlikely to be successful. This is essentially to better manage a difficult and uncontrollable glaucoma and not to improve vision. In glaucoma, already lost vision or lost visual field cannot be recovered or restored.

Vision once lost from glaucoma can not be regained. All treatment/operation for glaucoma is aimed at slowing down the rate of progression of glaucoma so that the risk of complete blindness in one's lifetime may be reduced.

How the glaucoma tube shunt implants work?

The tube shunt is a silicon tube and has an external diameter of 0.64 mm. One end of the tube is securely inserted into the eye (anterior chamber) and the other end is connected to a white silicon plate resting on the surface of the eye (sclera) acting like a reservoir for the water from inside the eye (aqueous) to be drained away and to be absorbed by the conjunctiva which is covering the silicon plate.

What is a donor sclera patch graft?

The glaucoma tube-shunt is going to stay in the eye for the lifetime, we use a piece of donor sclera (the white tissue of the eye) to cover the portion of the tube outside the eye to prevent exposure and displacement of the tube-shunt. The scleral tissues are obtained from deceased persons who donated their organs to be donated for medical use after death. They are sourced from the Human Tissue Bank in UK. The donors have been screened for any transmissible diseases except for prion infection, which could cause Creutzfeldt-Jackob disease [CJD] or spongiform encephalopathy, this is undetectable in the normal screening procedures. However, there in only a very remote chance for patients to acquire prion infection from receiving a donor tissue. Please discuss this with our glaucoma team if you have any concern about this.

The operation

This is usually performed under general anaesthesia (you are put to sleep during the surgery). The operation usually takes about 2- 2.5 hours to perform. After the operation and once you have completely recovered, you may go home. You will be given all the required medications and the team will make an appointment for you to be reviewed the next morning in the glaucoma clinic. If you are taking any blood thinning tablets (Warfarin or Aspirin), they might increase risk of bleeding during the operation. It might be advisable to stop them for a very short period before surgery provided this does not affect your general health. Please discuss this with the glaucoma team.

Do the tube-shunt implants work immediately after the operation?

The tube-shunt will not work immediately after the operation. We normally tie off the tube with a dissolvable suture to allow tissue to heal before the tube-shunt starts to work. It takes about 6 to 8 weeks for the suture to dissolve, during this time; patients should continue their glaucoma medications as instructed by the glaucoma team. In 6 weeks time, patients should stop using all the glaucoma medications and return to clinic as scheduled for check up. However, if the tube-shunt wasn’t tied due to some clinical circumstances, patients should stop all glaucoma medications immediately after the operation.

How successful is the tube-shunt implant surgery?

The tube shunt operation is generally a very successful operation for refractory glaucoma. The success rate is about 85% in 3 years in terms of successfully controlling the eye pressure. However, some patients may need to return to use one or more glaucoma eye drops to maintain a satisfactory eye pressure level. Further surgical or laser procedures may be required if a tube surgery fails.

What are the risks of the tube-shunt operation?

For some patients, the eye pressure could become too low (hypotony) when the tube-shunt starts working. Injection of some ‘jelly like’ substance (viscoelastics) into the front part of the eye may be necessary to maintain the eye pressure until it is stabilised. If the eye pressures remain too low, patients may need to undergo partial or total ligature of the tube-shunt to prevent complications from low eye pressure. Other risks of the operation include infection, reduced or loss of sight, bleeding inside the eye, cataract, double vision, droopy eyelid, pain, corneal haziness (decompensation), and very rarely retinal detachment.

What happen if the eye pressure elevates again after the tube-shunt operation?

The tube shunt is partially blocked by the supramid stent suture which reduces the tube function to only 10-20% to prevent low pressure. If the eye pressure starts to elevate again, the stent suture could be removed under local anaesthetics to allow the tube to function 100%. If the eye pressure is still too high due to excessive scar tissues forming over the tube-shunt drainage foot-plate, a needling procedure could be perform to perforate the scar tissues with injection of some anti-scarring agents, or laser treatment could be performed to aid the function of the tube-shunt.

Do I need to return to the glaucoma clinics if my eye pressure has become stabilised after a tube-shunt surgery?

Patients are still required to return to clinic for regular monitoring. The eye pressure could elevate again in the future or the tube position will need to be adjusted if it moves and becomes too close to the cornea. A cataract may also form earlier than usual, which may require a cataract operation.  

What to expect after tube surgery?

You will have an eye pad & shield which will be taken off in the clinic the next morning. You will have to take steroid tablets for 3 weeks on tapering doses and a few eye drops. If you feel you cannot take steroid tablet for any reason, talk with your glaucoma team. Your eye will be a bit gritty and sore for days to weeks. After your eye has settled down, the tube is usually not visible. You may however, feel the device under your upper eyelid. You will require close follow ups in the glaucoma clinic in the first 3 months after the surgery and therefore it is advisable not to be away or outside the country during this critical period. As the tube remains inside your eye, it is also advisable not to rub your eyes as this might cause potential contact and damage to other parts of the eye.

If you have any of the following after a tube implant surgery:

·        Sudden loss of vision

·        Severe and unrelenting pain

·        Any abnormal and increasing discharges

Please contact your local eye emergency service.

Further information:

http://www.amo-inc.com/products/cataract/glaucoma-implants/baerveldt-bg-103-250-glaucoma-implant