One way to relieve the dangerously high pressure in an eye with glaucoma is to make a new drain in the eye, a bypass for the blocked natural drain. This is called a trabeculectomy and takes the form of a “flap valve” which is surgically created in the white part of the eye hidden under the upper eyelid. The eye pressure is relieved because fluid can now drain through the new valve. A trabeculectomy is usually done under local and/or topical anesthesia. An anesthetist administers intravenous medication to relax the patient and reduce the discomfort of the local anesthetic injections. A shot of local anesthetic numbs the eye completely so that it will not move during surgery nor feel any pain. Alternatively, topical anesthetic drops and jell can numb he eye adequately for surgery. If preferred, the anesthesiologist can administer a general anesthetic, keeping the patient asleep for the whole operation. The surgery itself takes 35 minutes to an hour in most cases.
During trabeculectomy-sometimes also called filtration surgery-a piece of tissue in the drainage angle of the eye is removed, creating an opening. The opening is partially covered with a flap of tissue from the sclera, the white part of the eye, and the conjunctiva, the clear thin covering over the sclera. This new opening allows fluid (aqueous humor) to drain out of the eye, bypassing the clogged drainage channels of the trabecular meshwork.
As the fluid flows through the new drainage opening, the tissue over the opening rises to form a little blister or bubble, called a bleb. The bleb is located where the sclera, or white of the eye, joins the iris, the colored part of the eye.
Indications of trabeculectomy
Trabeculectomy is usually done when medicine treatment for glaucoma has failed to reduce the pressure in the eyes enough to prevent damage to a person's eyesight. It does not help to recover vision which is already lost in glaucoma.
Is it a permanent treatment?
The new opening created by trabeculectomy allows fluid to drain under the tissue that lines the eyeball (conjunctiva), where it is absorbed into the bloodstream.This procedure has been shown to reduce IOP and the need for medical treatment.1But many people need another trabeculectomy surgery or other treatments for glaucoma. Trabeculectomy is less likely to be successful in:
Shunts and Tubes
Glaucoma is a disease in which the drainage mechanism of the eye has become blocked. Since an eye normally produces a watery fluid called aqueous throughout life, this fluid has nowhere to go and backs up. This causes a build-up of pressure within the eye which injures the optic nerve. The safest and simplest type of surgery to reduce intraocular pressure is a trabeculectomy, a procedure which makes a flap valve on top of the eye. This allows the aqueous to seep out under this flap valve and be absorbed under the conjunctiva, the clear layer overlying the sclera, and into the bloodstream.
The ExPress mini-glaucoma shunt is a 400-μm wide by 3-mm long, stainless steel device that offers an additional option when treating difficult glaucoma cases. The device shunts aqueous from the anterior chamber to a subconjunctival reservoir in a similar fashion as trabeculectomy, without removal of any sclera or iris tissue. It provides immediate consistent aqueous flow through a 50-μm opening that allows for formation of a posterior, low-diffuse bleb usually limited to one quadrant.This technique has almost completely eliminated the erosion complication and has been demonstrated to have a lower rate of hypotony than trabeculectomy.