It tries to heal the cut. If the patient is too strong a healer and creates too much scar tissue, then the flap will seal down over the drainage hole and the pressure in the eye will again rise necessitating a return to drops and possibly pills to control the pressure. The eye usually has not lost any vision but will unless the pressure is reduced. In that circumstance, a trabeculectomy is usually done again with the addition of 5-FU or mitomycin, medications used to slow down the healing process. If the surgeon feels that the patient may heal too rapidly because they are young, black, have intraocular inflammation, or have had previous eye surgery, then one of these medications is often administered with the first trabeculectomy.
Results vary tremendously.
The second most common problem is related to the health of the eye. Because the drain of the eye, the trabecular meshwork, was blocked, the eye had only to make a limited amount of fluid to keep the pressure high. Many of the medications used preoperatively also cut down the eye's ability to make fluid. After the trabeculectomy, the part of the eye making fluid must adjust quickly to a now normal or slightly greater than normal size drain in the eye and increase its fluid output. In older patients, especially if the eye is not healthy, it may not be able to make this adjustment quickly.