Why have I been offered glaucoma surgery (trabeculectomy)?
Glaucoma is usually treated successfully with medication to lower the pressure in the eye. However, if medication is not effective, not tolerated (causing you side effects) and/or your glaucoma is getting worse, then trabeculectomy is usually required to lower/control the eye pressure (known as the intraocular pressure). Therefore, the aim of the operation is to lower/control your eye pressure to reduce your risk of visual loss. It will NOT improve your vision or reverse the damage which already been caused by glaucoma.
What is a trabeculectomy?
Trabeculectomy is a surgical operation which lowers the eye or intra ocular pressure (IOP) within the eye to help preserve vision. Any vision lost to glaucoma cannot be restored. The operation involves opening the skin of the eye (conjunctiva) under the upper lid to expose the wall of the eye (sclera). Atrap-door is made in the sclera and then a small hole is made in the remaining sclera beneath. The trap-door is sutured (stitched) with releasable sutures to prevent aqueous humour (fluid within the eye) from draining out of the eye too quickly. These sutures if required can then be removed (releasable sutures) in clinic after the surgery should the IOP be too high.
The skin of the eye (conjunctiva) is then replaced over the trap door in its original position and secured with sutures which are often removed in clinic if they are not buried in the conjunctiva. The whole operation site is covered by the upper eyelid.
The surgery works by draining fluid from within the eye known as aqueous humour, through the trap-door under the conjunctiva into a reservoir or bleb (figure 1). It is important to remember that the aqueous humour is fluid within the eye and is not related to the tears which cause the eye to water.
By draining aqueous humour in a controlled manner out of the eye, the trabeculectomy operation not only lowers the IOP, but also reduces fluctuation in the IOP.
Prior to surgery
Prior to surgery you should continue all your drops and tablets as normal even on the morning of the operation. Blood thinning medications (such as Aspirin, Clopidogrel, Wafarin) may be discontinued prior to surgery depending on the medical risk to you of stopping these treatments. This will be discussed with you at the time you are listed for surgery and again at a pre-operation assessment.
You may be called for a pre-operation assessment to document your medical history, medications and your fitness for the type of anaesthesia you will receive for the operation.
Organise someone to take you home after surgery. If you live alone and are having sedation then organise for someone to be with you at home for the night of the surgery incase you feel unwell.
Trabeculecomy surgery typically takes 60 to 80 minutes. Prior to commencing the surgery, the team will re-confirm your details such as your name, hospital number, date of birth, surgery and eye on which we are operating on.
The eye is then be cleaned with sterilising solution and then a sterile sheet will be placed over you to keep the site sterile for the duration of surgery.
The surgery will be performed as described above and then a shield and pad will be placed over the eye.
Trabeculectomy at Stoneygate Eye Hospital is either performed under:
1. Local anaesthesia (LA)– whereby a numbing medication (anaesthesia) is injected around the eye. The injection may cause mild discomfort and or a pressure sensation as it is delivered and this will quickly disappear. The injection anaesthetises the eye, preventing pain and excessive eye movements during the operation.
2. Local anaesthesia with sedation (LAS)-wherebyyou are given medication through the vein to make you ‘sleepy” but you will still be conscious and aware of your surroundings. The LA will be then be given around the eye to anaesthetise it. This choice of anesthesia will depend on a number of factors including age, other medical conditions and risk of complications and will be discussed with you at the time of listing for surgery.
If the operation is performed under LA or LAS you may hear the surgeon talking to the scrub nurse or other members of the surgical team which is quite normal and nothing to be concerned about.
During the surgery, the drug Mitomycin C is applied to the surface of the eye for 3 minutes and then washed away. Mitomycin C is a drug that was originally used to treat cancer and is used for glaucoma surgery to reduce scarring. Scarring is the main cause of trabeculectomy to reduce/stop functioning and the use of MMC reduces its risk.
Following the operation, you are usually examined by your consultant on the SAME DAY and then discharged home. Sometimes, you maybe seen the following day instead as well.
The eye is normally padded and a plastic shield is placed over the eye after surgery. The next day the eye pad and shield should be removed and the skin around the eye should be cleaned with cool boiled water. The pad can be disposed of, but the shield MUST be worn over the eye at night for 2 weeks. If you have poor or no sight in your other eye then we may take the pad off before you go home.
How should my eye feel or look like after the surgery?
After the operation, the eyelid on the operated eye may be droopy for the first 1-2 months. The eye will be ‘red’ and possibly ‘bloodshot’ for the first 4 weeks then this will settle. This is quite normal.
It is normal to feel itching, sticky eyelids and discomfort/soreness for a while (3-4 weeks) after trabeculectomy surgery due the surgery itself and partly due to the stitches. If you have soreness/discomfort, we suggest that you take a pain reliever such as paracetamol every 4-6 hours (but not aspirin or ibuprofen, as this can cause bleeding). Please don’t rub your eye.
The vision may be blurred after the surgery for the first few weeks and then starts to improve. It can take up to 3 months for the vision to stablise and sometimes a change of glasses prescription is required. However, a glasses test is not recommended until after 3 months following the surgery.
Eye drops after the surgery
After the surgery, all glaucoma drops to the OPERATED EYE ONLY and acetazolamide should be stopped. If you are using glaucoma drops for your other eye, these MUST be continued as normal.
Eye drops to the operated eye should start on the following morning after the operation. Typically, you will be given either 2 or 3 drops. It is important to leave a minimum of 5 minutes gap between any drops. You will be prescribed:
1. Antibiotic drop (Chloramphenicol preservative free): this is given four times a day and is to reduce your risk of infection. You will usually need to use this for 3-4 weeks.
2. Steroid drop (Dexamethasone preservative free): This is to reduce inflammation and therefore the risk of scarring which can lead failure of the surgery. The drops needs to be used for the majority of patients every 2 hours (during the day only) usually for the first month and then the drops are slowly reduced over 3 months at the surgeons discretion. You must NOT stop the steroid drops suddenly as your operation may fail. If you run out you must obtain the drops from your GP.
3. Pupil dilating drop (usually Atropine): This drop is SOMETIMES prescribed for patients who MAY develop complications if the IOP goes too low. The drop makes the pupil big and can protect the eye against low pressure. The drop is sually prescribed to be used twice a day and is used for the first 2-3 weeks (sometimes longer). The drop will make your pupil look bigger compared to the other eye and will blur your vision. However, once it is stopped the pupil and vision will return to normal, usually withinl 0-12 days.
Success of surgery
Trabeculectomy has a long track record of clinical evidence. Long term studies have shown that most people will achieve a low IOP without the need for additional medication. The success rate of trabeculectomy at controlling the IOP varies according to a number of risk factors including the type of glaucoma, previous surgery, ethnicity and age. In one study of trabeculectomy success, after 20 years, 57% were successful without medication and this increased to almost 90 % with additional IOP lowering medication. Put another way, just under two thirds required no glaucoma drops to control the IOP, whereas one third still required drops.
Risks of trabeculectomy surgery
Every operation carries a risk of complications. In most cases the complications can be treated and in a small proportion of cases, further surgery may be needed. Very rarely some complications can result in loss of sight.
Blurred vision/ loss of vision – Your vision is usually more blurred after the operation and may take several weeks to return to normal. Some patients will find that their vision is not quite as sharp after surgery. The vision generally stablises at around 3 months when you should see you optician for a glasses test. It is importantto remember than any vision lost due to glaucoma cannot be restored by surgery. Rarely (about 1:1000) patient develop blindness from the operation due to bleeding or infection of the eye.
High or low eye pressure – Your IOP may be high or low following surgery. If your IOP is high then, depending on how many weeks you are following the operation, we may either massage your eye pressure down (usuallyfirstweekfollowing surgery) or remove a suture (releasable suture) on your trabeculectomy. This is performed in the outpatient clinic following anaesthetic drop instillation. Your eye pressure will then be rechecked. After 3 months, if your IOP is too high then you either need drops again to lower your IOP and/or an operation called “bleb needling” whereby in the operating room with anaesthetic drops instilled in your eye or a local ananesthetic block, we break up the scarring around the trap-door with a needle in an attempt to get the trabeculectomy draining again. Infrequently, your IOP may be too low and you will need to be watched more closely with more frequent visits. If the low IOP is causing a reduction in vision or swelling at the back of the eye then you may need either a small injection of jelly into the eye or another operation to reduce drainage out of the trap-door by placing more sutures on the trap door.
Bleeding – There is a small chance of bleeding inside the eye immediately after surgery (called”suprachoroidal” haemorrhage). This may require further treatment, and may ultimately result in loss of sight.
Infection – There is a small chance of infection inside the eye after surgery. This may require further treatment, and may ultimately result in loss of sight. This operation will make your eye more prone to infection, even in years to come. If your eye becomes painful or red or the vision becomes blurred, you should seek immediate medical help.
Cataract – There is a reasonable chance that a cataract (cloudy lens) may develop some years after surgery. This may require an operation.
Irritation – Irritation (grittiness) or discomfort in the eye that may persist.
Droopy eyelid – Your eyelid may become droopy on the side of operation after surgery. This usually settles down and the eyelid position returns to normal/near normal. Rarely if the eyelid is still droopy after 3 months then you may need a small operation to lift the eyelid to match the other eye.
What symptoms should I look out for to seek medical attention?
Certain symptoms could mean that you need prompt treatment, including:
You will be given an emergency telephone number to ring in case you develop any of the above.
We hope this information is sufficient to help you decide whether to go ahead with surgery.
Author: Mr Rajen Tailor, Consultant Ophthalmologist