Trabeculectomy

What is a trabeculectomy?

 It is the operation that is most commonly performed for patients suffering glaucoma.

The purpose of this operation is to reduce the intraocular pressure and subsequently to stop or delay the progression of the glaucomatous damage. The operation involves creation of a small opening like a small hole in the wall of the eye (the white part of the eye). Through this hole the aqueous humor (the liquid that fills the front part of the eye) can leave the eye easier forming a small reservoir that is called a bleb. The bleb is normally not visible as it is cover by the upper eyelid. The small hole is covered by a trap-door or a flap of tissue of the wall of the eye that we fashion in a particular way. The flap is secured with sutures to prevent excessive drainage of the aqueous humor. These sutures can be adjustable or releasable and they are normally removed within 8 weeks after the surgery. Sometimes they don’t have to be removed if the intraocular pressure is low.

The duration of the surgery is approximately 45 to 60 minutes and can be performed either under local or under general anesthesia depending on the circumstances.

During the operation, we use a medication called mitomycin C which prevents the formation of scarring tissue. Excessive formation of scarring tissue can seal the small hole that we create and subsequently can compromise the success of the surgery causing the intraocular pressure to increase again.

Complications during the surgery are very rare. Sometimes complications can occur in the early or the late post-operative period.

How does the eye look after surgery?

 In the first days after surgery the eye may be red and slightly swollen. The upper eyelid may be slightly droopy. These symptoms subside a few weeks after surgery.

The drainage bleb is usually not visible. You can see it if you look in the mirror and lift your upper eyelid. Most of the time you do not feel the existence of the bleb. In rare cases where the bleb is too large in size and causes discomfort, further surgery may be necessary.

Do I need to alter my usual treatment before the surgery?

 You should continue your glaucoma medication (drops or pills) normally until the morning of the day of surgery.

If you are taking anticoagulants, you will be given special instructions by your surgeon or anesthetist. If you are taking aspirin, you can continue it normally.

In case of surgery under general anesthesia, a preoperative examination is necessary.

 What type of anesthesia is needed during the operation?

The operation lasts 45 to 60 minutes and is most often performed under local anesthesia. If you wish, you may be given a mild sedation. At the beginning we use anesthetic drops and then an injection of anesthetic fluid around the eye. This usually causes a feeling of pressure around the eye which lasts for a few seconds. The anesthetic injection is necessary because it avoids pain during the operation but also because it minimizes eye movements. It is normal to feel the surgeon’s hands resting on your forehead as this area is not numbed. If you feel pain or something bothering you during the operation you can ask the surgeon to stop and add more anesthetic.

What happens after surgery?

You can return back home on the same day. On the day of the operation and up to the next morning, the eye remains padded. In case that the other eye does not see well, we can use a transparent plastic shield to cover the operated eye. It is necessary to come for a follow-up appointment the next day after the surgery.

The vision can be slightly blurred after the surgery and also for the following 2-3 weeks. This is normal. Moreover, for few days after the surgery you may feel the eye slightly uncomfortable. This is due to some stitches on the surface of the eye. Normally these stitches are removed 4 weeks after the operation. Visual acuity normally stabilizes 3-4 months after surgery and after this is the appropriate time to test for new glasses if necessary.

Which medications do I need to use after surgery?

After the operation, you stop using the glaucoma drops in the operated eye. In the other eye you have to continue the drops as previously and you have to use them even on the day of the surgery.

After removal of the eye pad and cleaning of the eye on the 1^st post-operative day, you start using 2 different sorts of eye drops as well as an ointment at night time. One of the drops is an antibiotic and it is used 4 times daily for 1 month and the other one is a steroid anti-inflammatory, usually dexamethasone 0.1% and it is used very frequently, approximately 8 times daily the first weeks after surgery. The frequency of the steroid drops is reduced progressively and they are normally stopped 3-4 months after surgery.

What is the post-operative care?

The success of the operation depends on the post-operative care. That’s why post-operative follow-up appointments are very important. As the intraocular pressure may vary for few weeks after surgery, we normally see the patients once a week for the first 4 weeks. Rarely visits may be more frequent in case that the intraocular pressure goes very low or very high. During the post-operative visits, we may have to adjust or remove some stitches and also, we may need to inject anti-inflammatory or anti-scarring medications on the surface of the eye. After the 1^st month, the frequency of the visits is reduced and 4 months after surgery returns to the normal rate as before the surgery. If you are referred to us by another ophthalmologist colleague, you can return to his practice for your normal follow-up 3-4 months after the operation.

Which activities can I perform after surgery?

We recommend that you avoid strenuous exercise and heavy weight lifting during the first 4 to 6 weeks after surgery. If the intraocular pressure is very low, we may ask you to refrain from all activities and remain sedentary until the intraocular pressure is restored. Activities such as reading or watching TV do not harm the eye and can be practiced without restrictions.

When can I go back to work?

Returning to work depends on different factors such as the nature of employment, the visual acuity of the other eye and the intraocular pressure in the operated eye. Normally patients who work in an office stay off work for 2 weeks and patients performing manual work in a dusty environment stay off work for 1 month or even more.

Can I wear contact lenses after surgery? 

Normally you can wear contact lenses 4 week after surgery. On some occasions, contact lens wear is no longer possible after surgery due to the shape or the size of the filtering bleb. If it is absolutely essential to continue wear contact lenses, we have to opt for a different type of glaucoma surgery.

Can I fly after surgery?

There is no restriction to take the airplane after surgery. However, you need to bear in mind that frequent follow-up visits are necessary in the first 6-8 weeks and thus, it is advisable not to plan any trips in this period.

What is the success rate?

Long term multicenter studies show that the majority of the patients do not need anti-glaucoma medications after trabeculectomy for a number of years. Success rate can vary though depending on the type of glaucoma, previous intraocular operations, race, age and other factors. For patients without risk factors for failure, success rate reaches almost 90%. For the rest of the patient, we could estimate that 2/3 will achieve satisfactory control of the intraocular pressure without glaucoma drops and 1/3 will need glaucoma drops or further glaucoma surgery. In the rare occasion that the intraocular pressure remains too low for a long time and causes retinal complications, further surgery to increase the pressure may be required.

Which are the most common complications

The first post-operative days we may see fluctuations of the intraocular pressure and the pressure may go too low or too high.

If the pressure is too high, we normally perform ocular massage in the office or prescribe drops or rarely tablets to reduce the pressure before we can safely remove the stitches that keep the trap-door closed (usually 2 to 3 weeks after surgery).

If the pressure is too low, we prescribe some dilating drops and we alter the frequency of the post-operative medications. Moreover, we may recommend an injection of viscoelastic substance in the front part of the eye or further surgery to tighten the existing stitches or to add more stitches if necessary.  Overall, the risk of re-operation within the first month after trabeculectomy is about 5%.

The risk of serious complications such as serious infection or serious bleeding within the eye is about 1:500 to 1:1000.

Long term complications

Most common complications are infection, discomfort, cataract formation, upper eyelid ptosis and changes in spectacles’ prescription.

Sometimes, ocular hypotony (very low pressure) can result after trabeculectomy. However, the risk of low pressure is greater the first few weeks after surgery and normally as the time goes by, the pressure increases and stabilizes.

Infection

The risk of infection post trabeculectomy is very low, between 1:500 to 1:1000. Sometimes, few months of few years after surgery, the wall of the filtering bleb becomes very thin and the bleb can become infected. If you have been operated for trabeculectomy and your eye become red and sore, you notice discharge and blurring of the vision, then you have to consult an ophthalmologist in less than 24 hours. If the infection of the bleb spreads within the eye, can cause a various infection that is called endophthalmitis and that can severely affect your vision.

Discomfort

If the filtering bleb becomes large, it may extend below the eyelid and cause the eyelid to be raised or droopy.

A large filtering bleb can interfere with the surface of the eye causing discomfort or drying of the eye. This can occur in about 10% of patients and normally responds well to the treatment with lubricating eye drops. Occasionally, surgery may be required to reduce the size of the bleb in the case that the discomfort is severe.

Cataract

Trabeculectomy surgery may worsen the cataract in patients that have not been operated for cataract yet. This is due to fluctuations of the intraocular pressure and the frequent use of steroid drops that is necessary after surgery. If the cataract causes significant decrease in the visual acuity, cataract surgery can be performed and this restores vision. We normally wait 6 months after trabeculectomy surgery before we operate the cataract in the same eye in order to disturb as little as possible the intraocular pressure control achieved with the trabeculectomy.

Changes in spectacles’ prescription

Sometimes, spectacles’ prescription needs to be changed after surgery. We will check the prescription and prescribe new glasses if necessary 3-4 months after surgery. It is very rare that significant changes in the prescription are noticed or patients that didn’t require glasses before surgery develop need for glasses after surgery.