Trabeculectomy and sclerectomy – Filtering surgery
Trabeculectomy is a surgical procedure designed to reduce intraocular pressure in cases of glaucoma. Deep non-penetrating sclerectomy is another option that uses the same principles. A small valve is created between the inside of your eye and the space beneath your conjunctiva (the transparent membrane covering the white of the eye) to drain excess aqueous humor. This small valve lowers and regulates intraocular pressure to stop or slow the progression of your glaucoma. The operation has a success rate of 80 to 90%, although postoperative adjustments and touch-ups are necessary to control the flow of this valve. A thorough reading of this article will demystify the procedure and answer any questions you may have about postoperative care.
What is trabeculectomy for glaucoma?
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Trabeculectomy is the most commonly performed surgical procedure in the world for glaucoma.
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It helps to reduce the pressure inside your eye when medical treatments (eye drops) or consultation lasers (iridotomy and SLT) are not sufficient.
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During this operation, a small hole is made in the wall of the eye and a "valve" also called a "flap" or "surgery valve" is created above this hole to allow the fluid to escape from the eye in a controlled manner.
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The fluid is drawn from inside your eye, bypassing the trabecular meshwork and drains out through the small hole and the "trapdoor", while remaining under the conjunctiva (the transparent outer membrane of the eye covering the sclera).
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This forms a small blister or "bubble," invisible to the naked eye, under the upper eyelid. The drained fluid is absorbed by the blood vessels in the conjunctiva, so your eye will not water.
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Trabeculectomy is a very delicate operation, performed in the operating room under local anesthesia of the eye. It lasts approximately 30 minutes.
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After the operation, you will normally be able to stop using the glaucoma eye drops. However, you will need to strictly follow the postoperative treatment, which consists of antibiotic and anti-inflammatory drops, to prevent infection and control inflammation.
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Trabeculectomy is the most commonly performed glaucoma surgery worldwide. It is a penetrating surgery. Another option, developed in the 1980s, is called sclerectomy.
Non-perforating deep sclerectomy – SPNP
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Non-penetrating deep sclerectomy is a cousin of trabeculectomy. Developed in the 1980s, this operation is mainly performed in France and Russia, but less frequently in English-speaking countries.
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The procedure also involves creating an invisible “valve” and “bubble.” However, rather than making a small hole in the trabecular meshwork, the surgeon simply thins it over a large area.
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The procedure has the advantage of causing less inflammation. However, only patients suffering from open-angle glaucoma are eligible.
Filtering surgery
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Filtering surgery refers to all glaucoma procedures that divert aqueous humor beneath the conjunctiva. These include trabeculectomy, deep sclerectomy, and, less frequently, the insertion of drains or valves.
When should a trabeculectomy or sclerectomy be performed?
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In cases of glaucoma progressing under well-conducted medical treatment, your ophthalmologist may recommend a trabeculectomy to slow down or stop its worsening.
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Trabeculectomy is a possible treatment for closed-angle glaucoma, open-angle glaucoma, and primary and secondary glaucomas.
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Sclerectomy is only possible in cases of open-angle glaucoma.
A reminder about glaucoma
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Glaucoma is an eye disease in which excessively high eye pressure gradually damages your optic nerve.
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Damage to the optic nerve initially causes a loss of visual field (narrower vision) and then, in very late stages, a loss of vision.
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Without treatment, people with glaucoma therefore initially lose their peripheral vision and potentially their central vision over time.
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If not diagnosed in time or left untreated, glaucoma can lead to total blindness.
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Currently, all clinically proven glaucoma treatments involve lowering eye pressure to prevent further loss of visual field and then central vision.
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Most glaucoma patients are able to lower their eye pressure with the help of eye drops and/or in-office laser treatment.
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In cases of therapeutic failure with eye drops, contraindication or poor tolerance, filtering surgery is frequently indicated.
The operation
Before surgery – Preparing
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Glaucoma surgery is performed on an outpatient basis. You will not spend the night in the hospital or clinic.
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You will need to attend an anesthesia consultation before the procedure. The anesthesiologist will ask you to continue your usual treatments except for anticoagulants, which will need to be stopped in certain circumstances.
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On the day of the procedure, arrive fasting (without having eaten, drunk, or smoked, 6 hours before the scheduled time).
The operation
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The procedure is performed under local anesthesia of the eye. Anesthetic eye drops and an injection under the conjunctiva prevent any pain.
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The surgeon will be working in sterile conditions; you will be covered with a sterile drape, leaving only the eye to be operated on exposed. You will be blinded by the microscope light and will not see the surgeon operating.
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A blepharostat will keep your eye open.
The steps of the operation:
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Detachment of the conjunctiva at the upper periphery of the eye.
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Creation of a thin scleral flap (valve) giving access to the trabecular meshwork.
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Perforation of the trabeculum (trabeculectomy) or thinning thereof (sclerectomy).
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Instillation of an anti-scarring agent (5-FU or Mitomycin) under the conjunctiva to prevent excessive scarring.
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Conjunctiva sutured with 2 absorbable suture threads.
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The conjunctiva opposite the flap will become the filtration bubble.
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You will leave the operating room with a protective shield over your eye.
After the operation
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You will be able to return home 1 to 2 hours after the procedure. Start the eye drops the day after the operation.
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An initial eye pressure check is usually scheduled for the following day. It will almost certainly be low.
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Vision is very blurry after the operation; it will gradually improve over 3 to 4 weeks.
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Regular eye pressure checks will be scheduled for the first two months following the procedure. In the event of excessive scarring and a rise in pressure, touch-ups will be recommended to release the valve and reactivate the bubble. This does not indicate surgical failure but rather frequently necessary adjustments.
Success factor: wound healing management
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The success of trabeculectomy and sclerectomy depends not only on the procedure itself, but also, and perhaps most importantly, on your healing.
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Follow-up visits to adjust postoperative treatment and management of the "bubble" are planned for the first 2 months (3 to 4 visits on average).
In addition to anti-inflammatory eye drops, the surgeon may suggest the following adjustments:
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Eye massage to “force” the valve and increase the drainage flow until it stabilizes.
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Cutting a suture thread to release the "flap", using a needle or laser.
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Needling – Scraping of the blister to remove fibrosis and injection of an anti-scarring agent (5-FU).
A closer look at fibrosis
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Often, the "trapdoor" or "bubble" heals excessively.
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This is a normal reaction of your eye as part of the healing process. However, after glaucoma surgery, it is essential to limit this scarring to maintain the effectiveness of the operation.
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The surgeon routinely uses Mitomycin-C or 5-fluorouracil (5-FU) during the operation to try to prevent this excessive scarring, but it sometimes still happens.
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In this case, the intraocular pressure rises again and it is necessary to "reactivate the blister". To do this, the surgeon uses a needle to release the areas of fibrosis and injects an anti-scarring agent (5-FU) into the blister.
Risks and complications of trabeculectomy
Many patients will see their intraocular pressure and glaucoma stabilized permanently. However, some patients will experience more complex post-operative issues, or even complications. The main ones are:
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Ocular hypertension – This is a failure of surgery to control intraocular pressure. It usually occurs due to excessive scarring at the surgical site. This fibrosis impedes the drainage of aqueous humor. If this occurs, the surgical site can be surgically revised by removing the scar tissue. A second operation can also be performed nearby to lower intraocular pressure.
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Fluid leak from the filter bubble – Sometimes the leak resolves itself, but further surgery to repair the leak is sometimes necessary.
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Hypotony – If the procedure results in excessive drainage of fluid from inside the eye, intraocular pressure can become too low. Vision becomes blurred due to this overly soft eye.
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Intraocular bleeding – Bleeding inside the eye can occur following a trabeculectomy, particularly in cases of severe or prolonged hypotony. It may resolve on its own as pressure increases or may require surgical drainage.
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Infection of the filtering bleb – There is a risk of infection at the surgical site, either immediately after the procedure or many years later in cases of delayed leakage. Therefore, any conjunctivitis in a patient who has undergone glaucoma surgery must be treated seriously!
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Cataracts – The lens, the eye's natural focusing lens, naturally becomes cloudy with age; this is called a cataract. Trabeculectomy is known to accelerate cataract formation, but the surgery itself yields excellent results.
Your surgical risks can vary depending on your age, health, the anatomy of your eye, and the severity of your glaucoma. Regardless of the outcome, never refuse the adjustments recommended by your surgeon to ensure the long-term success of the operation.
Frequently Asked Questions
Should hypotensive eye drops be continued after a trabeculectomy?
No! After filtering surgery, it is essential to stop using hypotonic eye drops. The success of the operation depends on it.
Does trabeculectomy improve vision?
No! Trabeculectomy is meant to lower intraocular pressure, but it won't improve your vision. In glaucoma, what's lost is lost, and no treatment can improve your field of vision or visual acuity.