A trabeculectomy is used in the treatment of glaucoma to lower the pressure in the eye. Often this is done when you cannot take higher doses of the medicines you need to lower the pressure in your eye. If the pressure remains too high, it can damage the optic nerve and your vision.
A small opening is made in the white sclera of the eye to create a drainage channel for fluid from the inside of the eye. This hole is covered by a thin tissue, the conjunctiva. When the fluid flows through this hole, it collects under the conjunctiva and forms a small blister. The fluid under the blister is slowly absorbed by the body. Doctors look for the blister to be sure that the fluid is draining the way it should.