The aim of a trabeculectomy is to create a permanent flow of fluid from inside the eye to the area under the skin that surrounds the eye, called the conjunctiva. As shown in the animation, a small opening is made in the outer wall of the eye (sclera). The opening is covered by a thin “trap‐door” in the sclera. As a result, there is a communication between the inside of the eye and the area under the conjunctiva where the fluid drains and forms a small blister-like reservoir (bleb) just under the eye surface. The bleb is not visible as it is hidden under the eyelid. The flow rate of the fluid determines the level of the eye pressure. This can be adjusted, as special sutures are placed on the “trab-door”, which can be removed in the clinic if the eye pressure is not low enough.
The natural reaction of the human body to any surgical procedure is healing. However, in trabeculectomy healing causes scarring, which would cause the operation to fail as it would block the new drainage channel. To prevent scarring, a special anti-scarring substance, called Mitomycin C is applied under the conjunctiva in almost all cases.
The operation is usually performed under local anaesthesia. However, general anaesthesia is available for anxious patients.