The surgical management of glaucoma is offered to patients if drug therapies have not been satisfactory or are inappropriate (e.g., because of the desire to avoid drugs during pregnancy). There are two types of surgical treatment: those using a laser and those using surgical techniques.
Laser surgeries lower intraocular pressure by enhancing the drainage of aqueous fluid or slowing its production. The kind of laser surgery used depends on the type of glaucoma being treated. The length of time the pressure remains lowered depends on the type of laser surgery, the type of glaucoma, and the patient's individual characteristics.
In some cases, laser surgery may have to be repeated to control internal eye pressure more effectively. Typically, medications will still be needed to maintain fluid pressure within the eye, although a lower dose than previously used may be sufficient. If the laser therapy does not lower the pressure in the eye satisfactorily or the effects wear off, the surgeon may recommend conventional (filtrations) surgery.
If despite treatment with eyedrops the IOP remains high and there is evidence of progressive visual field loss glaucoma surgery may be needed to prevent further damage to your vision. This operation is called a trabeculectomy and can be performed alone or it can be combined with a cataract removal.
Like cataract surgery the vast majority of trabeculectomies are carried out under a local anaesthetic. Local anaesthetic is injected around the eye - this stings a little. A pad or small balloon is then placed over the eye for 5-10 minutes. Once the local anaesthetic has taken effect you will not be able to see or feel what is happening, nor will you be able to move the eye or blink. During the operation you may occasionally see bright or coloured lights and you may be aware of the surgeons hands resting on your forehead and/or face.
The operation is performed under a microscope and involves making a special type of small trap door in the sclera (white outer coat of the eye). A small segment of the iris is then removed to prevent it floating up and blocking the trapdoor. The scleral trapdoor is then closed with microscopically fine stitches so that the fluid in the eye may drain slowly out of the eye so reducing the pressure. Your surgeon may use a specialized technique which allows the tension in these small stitches to be adjusted after the surgery or for them to be removed altogether. This means that the drainage of fluid can be improved a simple maneuver carried out in the outpatient clinic.
Your surgeon may also use a special medicine, applied to the eye for a few minutes by a very small sponge, to slow down or prevent subsequent healing and sealing up of the trapdoor. Useful medicines include 5FU and mitomycin C. The drapdoor is then covered by the conjunctiva, the clear tissue on the surface of the sclera, and this is carefully stitched in position.
The leaking fluid collects underneath the conjunctiva and lifts it very slightly to form what is called a "bleb". This may sometimes look like a small cyst.
Camden Medical Centre,
1 Orchard Boulevard,
Tel: 6738 2000
Fax: 6738 2111