An In-Depth Look at Iridotomy and Iridectomy Surgery

The purpose of iridotomy or iridectomy surgery is to prevent or treat a form of glaucoma known as angle-closure glaucoma (also known as acute glaucoma or acute angle glaucoma), a painful vision-threatening emergency.

This condition occurs when fluid is unable to drain from the eye or circulate properly through it (for reasons we will explain in greater detail below), causing a buildup of eye pressure that can damage the optic nerve, resulting in vision loss, or even blindness.

Why Are Iridotomy or Iridectomy Surgeries Performed?

Generally speaking, iridotomy or iridectomy surgery is performed on people who have narrow angles or suffer from narrow-angle glaucoma, and may therefore be at risk for an attack of angle-closure glaucoma.

First, let’s define some of these terms, starting with angle:

The angle is the place where your iris (the colored part of your eye) meets the cornea. As the name suggests, an angle is formed by the intersection of these two planes. Within this space is a drainage system called the trabecular meshwork, through which the aqueous humor drains (the aqueous humor is the fluid within your eye).

The anterior chamber at the front of your eye is the fluid-filled space between the cornea and the iris and lens (if you would like a clearer picture of the anatomy of your eye in order to understand all this, click here).

In a person with narrow angles, the iris bows forward somewhat, narrowing the angle through which fluid drains. This itself is not necessarily a problem, as not everyone with narrow angles develops glaucoma.

However, people with narrow angles—and far-sighted people, who have smaller anterior chambers—are more prone to narrow-angle glaucoma, which occurs if the normal drainage of fluid is blocked by the iris, which may begin to cover the drainage canals. This leads to a buildup of fluid that increases pressure within the eye, particularly within the anterior chamber. Left untreated, this pressure buildup can damage your optic nerve.

People who have narrow angles are at risk for an attack of angle-closure glaucoma, which occurs when the angle is no longer narrow, but has closed completely, effectively shutting down your eye’s drainage system. This is a sight-threatening medical emergency, and if this happens to you, you need to seek medical attention at once—permanent damage to your vision can occur within a matter of hours. This can happen with little or no warning; in susceptible people, it is even possible for acute angle closure to be triggered by walking from a brightly-lit environment into a dark room.

Symptoms of acute angle-closure glaucoma include intense eye pain and headaches, and even nausea and vomiting. These symptoms will generally be accompanied by blurred vision, and often by red-eye and halos around lights.


An iridotomy involves the use of surgical instruments—or more often, a laser—to punch a tiny, half-millimeter hole in the iris through which the trapped fluid can drain. First, an eye drop known as pilocarpine is applied to the eye in order to constrict the pupil (make it smaller), thereby making the iris thinner as its tissue expands. Then an anesthetic eye drop is used to numb the eye.

Once this is done, a laser will be used to make the drainage hole. This hole will not affect the patient’s vision, and it is usually placed at the far edge of the iris, under the eyelid, out of view.

For the first hour following the procedure, the patient may experience blurred vision, but this usually passes quickly. About an hour after surgery the patient’s intraocular pressure will be checked to make sure it has not risen, which occasionally happens. If the patient’s eye pressure has risen more eye drops will be applied to lower it. Anti-inflammatory eye drops will usually be prescribed for the patient to use several times a day for a few days.

Iridotomy is performed for a number of reasons: It is often done for people who have narrow angles, in order to prevent narrow angle glaucoma or a possible future occurrence of acute angle closure. If such an event occurs, however, iridotomy can also be used to treat the emergency condition and prevent recurrence.

If a patient suffers from narrow-angle glaucoma or has suffered an attack of acute angle closure in the past, many eye doctors will strongly recommend preventive iridotomy of the other, unaffected eye, since that eye stands at least a 50 percent chance of being similarly affected in the future.

Risks and Possible Complications of Iridotomy

All surgery involves some degree of risk. For iridotomy those risks include bleeding and inflammation, and possible rises in eye pressure. Such complications are not common, however.

In some cases a second procedure will be necessary; this is more likely if the patient has brown eyes, rather than blue or green, as these irises tend to be thicker. A small number of patients report that they see more glare around lights at night.

There is a small amount of evidence that iridotomy can encourage the development of cataracts, but this is not necessarily proven. Regardless, the risk is incredibly slight compared to the risks associated with angle-closure glaucoma—which can often cause a cataract to develop anyway.


Iridectomy is a similar procedure to iridotomy, and it is usually performed for similar reasons. The difference is that rather than creating a hole in the iris, the surgeon removes part of it. There are several types of iridectomy:

  • A peripheral iridectomy removes a portion of the iris at the root, where the pupil is.
  • A basal iridectomy removes the root itself.
  • An optical iridectomy enlarges the pupil.
  • A sector iridectomy removes a section of the iris in the shape of a tiny slice of pie.