Trabeculectomy and Postoperative Care
What is a trabeculectomy?
A trabeculectomy is an operation performed to lower the pressure inside the eye (intraocular pressure, or IOP) in patients with glaucoma. The aim is to protect the optic nerve from further damage and, where possible, prevent further loss of vision.
Glaucoma occurs when the optic nerve becomes damaged, usually in association with raised or otherwise inadequately controlled IOP. Eye drops, laser treatment and other procedures may be sufficient for many patients. However, if the pressure remains too high despite treatment, if glaucoma is progressing, or if medication is poorly tolerated, surgery may be recommended.
A trabeculectomy creates a new drainage pathway through which aqueous fluid can leave the eye. The fluid passes underneath the conjunctiva, forming a small reservoir known as a filtering bleb. The bleb allows fluid to drain gradually and thereby lowers the pressure within the eye.
Trabeculectomy remains one of the most effective operations for achieving substantial and sustained IOP reduction.
The operation
Trabeculectomy is usually performed under local anaesthesia, sometimes with sedation. The eye is made completely numb, and the patient should not experience pain during the operation. General anaesthesia may occasionally be appropriate for patients who are unable to tolerate surgery while awake or who cannot reliably remain still.
A small flap is created in the sclera, the white outer coat of the eye. A controlled opening is then made into the anterior chamber, allowing aqueous fluid to drain beneath the conjunctiva. The scleral flap is secured with fine sutures. These sutures may be adjusted or released after surgery to control the rate of drainage.
An anti-scarring medication, most commonly mitomycin C, is usually applied during the operation. This is important because the body’s natural healing response can cause scar tissue to form around the drainage pathway and cause the operation to fail.
At the end of surgery the eye is normally covered with a pad or protective shield.
What should I expect immediately after surgery?
Trabeculectomy is different from cataract surgery in that the eye requires careful and relatively intensive postoperative management.
The pressure can be quite low during the early postoperative period while the new drainage pathway is settling. This is often intentional and can be acceptable provided the eye remains structurally healthy. Conversely, the pressure may sometimes remain higher than desired, particularly if the drainage pathway is initially restricted by the scleral flap or early scarring.
For this reason, postoperative examinations are particularly important.
The first review is generally performed within the first few days after surgery, followed by further appointments according to the appearance of the eye and the IOP.
The eye may be uncomfortable, gritty or watery for several days. Vision is commonly blurred initially and may fluctuate substantially during the first few weeks. This does not necessarily indicate a complication.
Postoperative eye drops
Patients are normally prescribed several different drops following trabeculectomy.
A steroid drop is particularly important because it suppresses inflammation and, importantly, reduces the healing response that can cause the trabeculectomy to scar. Steroids are generally used much more intensively and for much longer than after uncomplicated cataract surgery.
The frequency may initially be very high—for example, every one to two hours while awake—and is then gradually reduced according to the clinical appearance of the eye.
An antibiotic is commonly used for a shorter period after surgery to reduce the risk of infection.
Glaucoma medications used before surgery are often stopped initially in the operated eye because the purpose of the trabeculectomy is to achieve pressure control without them. However, medications may need to be restarted if the IOP subsequently rises.
It is essential that drops are used exactly as instructed. Patients should not reduce or stop steroid treatment themselves, even if the eye feels comfortable, because doing so can increase the risk of scarring and failure of the trabeculectomy.
The importance of postoperative visits
The success of trabeculectomy depends not only on the operation itself but also on the postoperative period.
The surgeon will assess:
intraocular pressure;
the appearance and function of the filtering bleb;
the depth of the anterior chamber;
inflammation within the eye;
wound integrity;
the position and tension of the scleral flap sutures;
the optic nerve and retina where appropriate.
The treatment can then be adjusted according to these findings.
One of the advantages of trabeculectomy is that the surgeon can modify the operation after surgery. This is sometimes referred to as bleb manipulation or postoperative titration.
Suture adjustment and laser suture lysis
The scleral flap is commonly secured with very fine sutures. These can sometimes be adjusted using a laser after surgery.
If the pressure remains higher than desired because the flap is draining insufficiently, one or more sutures may be released with laser treatment. This can increase aqueous drainage and lower the IOP.
This is one reason why the postoperative period should be regarded as part of the trabeculectomy procedure rather than simply a period of recovery.
Needling and 5-fluorouracil
Sometimes the drainage bleb begins to scar or does not function adequately. In this situation, a procedure known as bleb needling may be required.
Under local anaesthesia, a fine needle is used to release scar tissue around the bleb and restore its ability to drain fluid. An anti-scarring drug such as 5-fluorouracil (5-FU) may be injected at the same time.
Needling may be performed at the slit lamp or, depending on the circumstances, as a more formal procedure. Several treatments may occasionally be necessary.
Needling is an important part of modern trabeculectomy management and does not necessarily mean that the original operation has failed. It can be an effective method of rescuing a filtering bleb that is becoming restricted by scar tissue.
Activity after surgery
The eye should be protected during the early healing period.
Patients should avoid rubbing or pressing on the eye. A protective shield may be recommended at night initially.
Strenuous exercise, heavy lifting and activities that could result in direct trauma to the eye are generally restricted during the early postoperative period. Swimming is usually avoided until the eye has adequately healed.
Normal activities can gradually be resumed according to the surgeon’s advice.
Vision may fluctuate, particularly while the IOP is changing and while the eye is inflamed. Patients should therefore be cautious about driving and should only resume driving when their vision meets the appropriate legal requirements and they feel safe to do so.
Warning symptoms
Patients should seek urgent ophthalmic advice if they develop:
a significant or sudden deterioration in vision;
increasing or severe pain;
marked redness;
increasing discharge;
pronounced sensitivity to light;
new flashes or a large increase in floaters;
a feeling that the eye has suddenly become very soft;
trauma to the operated eye.
In particular, pain, redness and deterioration in vision should not simply be assumed to represent normal postoperative recovery.
One of the most serious complications following trabeculectomy is infection of the filtering bleb or inside the eye. Although uncommon, this can be sight-threatening and requires urgent treatment.
Possible complications
Trabeculectomy is a major glaucoma operation and, although highly effective, it has potential complications.
These include excessively low IOP, shallow or flat anterior chamber, choroidal effusion or haemorrhage, inflammation, infection, wound leakage, cataract progression, changes in vision and failure to achieve adequate pressure control.
A particularly important early complication is hypotony, where the pressure becomes too low. Mild hypotony may simply require observation and adjustment of treatment, but significant hypotony can occasionally affect the retina or other structures within the eye.
Conversely, the pressure may remain too high. This may require additional medication, laser suture lysis, bleb manipulation, needling or, occasionally, further glaucoma surgery.
The filtering bleb itself can change over time. A successful bleb may remain functional for many years, but scarring can develop at any stage.
There is also a lifelong, although small, risk of late bleb-related infection. Patients who have undergone trabeculectomy should therefore inform future healthcare professionals that they have a filtering bleb and should seek urgent ophthalmic assessment if they develop unexplained redness, pain or deterioration in vision.
Long-term follow-up
Trabeculectomy is not the end of glaucoma treatment. It is a means of achieving better pressure control and protecting the optic nerve.
Patients require lifelong glaucoma surveillance, even when the IOP is excellent. The pressure may gradually increase again, the bleb may change, or glaucoma may progress despite apparently satisfactory pressure measurements.
Long-term follow-up will usually include measurement of IOP and assessment of the optic nerve, visual fields and, where appropriate, OCT imaging.
The target pressure is individual to each patient and depends on the extent and rate of glaucoma damage and other risk factors.
Conclusion
Trabeculectomy is an effective operation for lowering IOP and is capable of achieving a level of pressure control that may not be possible with eye drops or less invasive treatments.
The postoperative period is an essential part of the treatment. Intensive steroid drops, frequent examinations and, when necessary, interventions such as laser suture lysis or bleb needling are often required to achieve the best possible result.
The operation should therefore be regarded as a process rather than a single surgical event. The surgeon deliberately creates a drainage pathway and then carefully manages the healing response during the following weeks and months.
With appropriate postoperative care and long-term monitoring, trabeculectomy can provide excellent and durable pressure control and substantially reduce the risk of further glaucoma damage. However, it requires careful adherence to postoperative treatment and prompt reporting of any concerning symptoms.