GONIOTOMY EYE SURGERY RISKS RESULTS

Since goniotomy is performed under general anesthesia, there is some risk of a reaction to the anesthetic. The most common risk of general anesthesia in infants is cardiorespiratory arrest. This complication is not lifethreatening, however, and occurs in fewer than 2% of goniotomies. A hyphema (bleeding and formation of a blood clot in the anterior chamber) is the most common complication of a goniotomy. In most cases, however, the blood clots resolve within a few days. If the cornea is not clear during surgery, the surgeon may accidentally sever the iris from the ciliary body or separate the ciliary body from the sclera of the eye. Both of these complications can lead to hypotony, a condition in which the integrity of the eye is compromised because of insufficient intraocular fluid. Other complications of goniotomy are cataract formation; inflammation in the anterior chamber; scarring of the cornea; subluxation or dislocation of the lens; and retinal detachment. The risk of damage to the lens is greater when the patient is aniridic. The intraocular pressure may increase in spite of, or due to complications of the procedure, and the goniotomy may have to be repeated. If the goniotomy is not successful after two or three attempts, the surgeon will perform a trabeculotomy.

Normal results
Goniotomy is considered to be successful when the measured IOP is below 21 mm/Hg, or below 16 mm/Hg if the patient is under anesthesia; when there is no increase in corneal diameter; and when damage to the optic nerve is stabilized or even reversed. Goniotomy is successful in about 94% of patients with primary congenital glaucoma in decreasing IOP, corneal haze, and corneal diameter. Tearing, sensitivity to light, and blepharospasm all decrease over time.

If a goniotomy is successful it will be apparent within three to six weeks. A repeat goniotomy is required for 50% of patients. Goniotomy is most successful when the child is between one month and three years of age; it is successful only a quarter of the time in patients younger than one month. It is also more successful when the corneal diameter is less than 14 mm and when the IOP is not extremely high. Even if the IOP has been lowered, anti-glaucoma medication or drops may still be needed after the goniotomy. When a goniotomy is performed on patients with uveitic glaucoma, the success rate is 75%–83%, although most of these patients need ongoing medication for glaucoma, and 30% require a repeat procedure.

Morbidity and mortality rates
Fifteen years after a goniotomy, one in seven patients will have such serious complications as corneal decompensation or detachment of the retina. Vision loss occurs in 50% of children with congenital glaucoma in spite of surgical and medical intervention. This is particularly true of infants diagnosed with glaucoma before two months of age. About 50% of children who undergo goniotomy require a repeat procedure. Complications are more common for patients treated as young infants and as older children.

Alternatives
Congenital glaucoma does not respond well to medical treatment, so the first line of treatment is usually surgical. Medical therapy is often initiated as adjunct therapy after surgery.

One alternative to goniotomy is trabeculotomy. Goniotomy has been the preferred procedure for treatment of congenital glaucoma, but trabeculotomy has been favored in recent years because of the surgeon’s difficulty in seeing the structures in the eye when the cornea is hazy. A clear view of the cornea is required for goniotomy. In a trabeculotomy, the surgeon inserts a probe into the eye, passes it through Schlemm’s canal, and rotates it inside the anterior chamber in order to tear a hole in the trabecular meshwork. This maneuver creates an alternative passageway for the aqueous fluid to leave the anterior chamber of the eye. In some cases the surgeon will perform a trabeculectomy, a procedure in which part of the trabecular meshwork is removed by cutting, at the same time as the trabeculotomy.

Another alternative procedure involves placement ofa filtering shunt to direct the intraocular fluid out of the eye. A shunt is often placed if Schlemm’s canal cannot easily be located, as in the case with infants. The safety profile for trabeculotomy and filtering surgery are comparable to goniotomy, but there is a higher rate of longterm success with goniotomies and trabeculotomies. A newer variation of surgical goniotomy is laser goniotomy, in which the surgeon uses a Yag:Nd laser to cut into the trabecular meshwork. Laser goniotomies appear to be less effective than surgical goniotomies, but if a patient responds well to a laser procedure, then surgical goniotomy may be considered.

Other alternative treatments for pediatric glaucoma are the cyclodestructive techniques, which include cyclophotocoagulation, and the more commonly performed

cyclocryotherapy. These procedures involve destruction of the ciliary body by using either freezing temperatures or lasers. These procedures have lower success rates and a higher risk of complications; they are usually performed as a last resort when other techniques have failed.