When medicines and laser surgeries do not lower eye pressure adequately, doctors may recommend a procedure called filtering microsurgery (sometimes called conventional or cutting surgery).
In filtering microsurgery, a tiny drainage hole is made in the sclera (the white part of the eye) in a procedure called a trabeculectomy or a sclerostomy. The new drainage hole allows fluid to flow out of the eye and helps lower eye pressure. This prevents or reduces damage to the optic nerve.
Is There Pain During the Surgery?
In most cases, there is no pain involved. The surgery is usually done with a local anesthetic and relaxing medications. Often a limited type of anesthesia, called intravenous (I.V.) sedation, is used.
In addition, an injection is given around or behind the eye to prevent eye movement. This injection is not painful when I.V. sedation is used first. The patient will be relaxed and drowsy and will not experience any pain during surgery.
Most of the related studies document follow-up for a one year period. In those reports, it shows that in older patients, glaucoma filtering surgery is successful in about 70-90% of cases, for at least one year.
Occasionally, the surgically-created drainage hole begins to close and the pressure rises again. This happens because the body tries to heal the new opening in the eye, as if the opening were an injury. This rapid healing occurs most often in younger people, because they have a stronger healing system. Anti-wound healing drugs, such as mitomycin-C and 5-FU, help slow down the healing of the opening. If needed, glaucoma filtering surgery can be done a number of times in the same eye.
Usually, filtering surgery is an outpatient procedure, requiring no overnight hospital stay. Within a few days after surgery, the eye doctor will need to check on the eye pressure. The doctor will also look for any signs of infection or increase in inflammation.
For at least one week after surgery, patients are advised to keep water out of the eye. Most daily activities can be done, however, it is important to avoid driving, reading, bending, and doing any heavy lifting.
Each case is different, so check with your doctor for specific advice.
Appearance of the Eye after Surgery
The eye will be red and irritated shortly after surgery, and there may be increased eye tearing or watering. The inner eye fluid flows through the surgically-created hole and forms a small blister-like bump called a bleb. The bleb, usually located on the upper surface of the eye, is covered by the eyelid, and is usually not visible.
Changes in Vision and Medication
There may be some vision changes, such as blurred vision, for about six weeks after the surgery. After that time, vision will usually return to the same level it was before surgery.
Vision can sometimes improve after surgery in patients who had been using pilocarpine. After stopping pilocarpine drops, the pupil returns to normal size, allowing more light to enter the eye.
In a few cases, the vision may be worse due to very low pressure. Cataracts or wrinkle in the macula area of the eye may develop.
After surgery, you may need to change your contact lenses or glasses. Gas permeable or soft contact lenses may be worn. However, the bleb may cause fitting problems, and special care will be needed to avoid infection of the bleb. Contact lens users should discuss these problems with their eye doctor following surgery.