Last updated: 11/24/2009

To determine if laser iridotomy is indicated, the surgeon must first determine if and how the angle is occluded. The eye is anesthetized and the aonioscopic lens, which enables the surgeon to see the interior of the eye, is placed on the front of the...

eye. This is done at the slit lamp biomicroscope in a dark room. In cases of prophylactic surgery, an image of the eye is taken with a ultra-sound biomicroscope in both dim and bright light; this shows the doctor how the patient's iris moves with dilation and constriction, and how this movement can close an angle if the patient has ocular features that predispose the eye to an angle closure.

When an angle is completely occluded (blocked), the elevated IOP usually causes corneal edema (swelling). Because this swelling can obscure the surgeon's view of the iris, prior to performing a laser iridotomy, the IOP must be lowered. One technique to lower the IOP is corneal indentation, in which the gentle pressure is applied several times to the cornea with a lens or hook to open the angle. This pressure on the cornea causes a shift in the internal structures of the eye, enhances aqueous drainage, and lowers the IOP.

The doctor can attempt to lower the IOP medically, as well. One drug that lowers the pressure is acetazolamide, which is given either orally or by intravenous(IV) to decrease aqueous production in the eye. This may be administered up to four times a day, until the adhesion is broken. Another method of lowering the IOP, if acetazolamide is not effective, is with the use of hyperosmotic agents, which through osmosis causes drainage of the aqueous fluid from the eye into the rest of the body. Hyperosmotic agents are given orally; an example of such an agent is glycerine. Given by IV (intravenous administration), mannitol can be used. As the fluid drains from the eye, the vitreous—the jelly-like substance behind the lens in the posterior chamber—shrinks. As it shrinks, the lens in the eye pulls away from the vitreous, creating an opening to the anterior chamber such that aqueous fluid can flow to the anterior chamber. The success of this procedure is increased, due to gravity, if the patient is laying supine.

Once the IOP has begun to decrease, the pressure is further decreased using topical glaucoma medications, such as pilocarpine, or beta blockers. Any inflammation that occurs because of the iridotomy must be controlled with steroid eye drops.

If glaucomatous-like visual field is present prior to surgical intervention, the prognosis for the patient is not as good as if the visual field were completely intact. Thus, a visual field test may be done prior to surgery.