Angle-closure Glaucoma
Chat Highlights
January 17, 2007

On Wednesday, January 17, 2007, Dr. Rick Wilson, a glaucoma specialist at Wills, and the glaucoma chat group discussed "Angle-closure Glaucoma."

Moderator:  Tonight's topic is angle-closure glaucoma.  First, where is the angle of the eye?

Dr. Rick Wilson:   The angle of the eye is where the cornea meets the sclera and the iris inserts into the wall of the eye.  That is where the drain of the eye is, just in front of the iris on the corneal side.  The outflow track extends all around the inside of the eye as a narrow meshwork that leads into Schlemm's canal.  The canal leads into veins that transport the eye's fluid into the blood stream.

P:  What is angle-closure glaucoma?

Dr. Rick Wilson:  In angle-closure glaucoma, the trabecular meshwork (the inner opening for the drain of the eye) gets covered by a variety of things.  The most common type of angle closure occurs when the eye is small and the iris is located too close to the drain.  When the pupil expands, the iris gets too close to the trabecular meshwork and covers it.  That stops the flow of fluid out of the eye.  Since the eye keeps making fluid at a normal rate, but the fluid is not leaving the eye, the pressure builds quickly.  Women have smaller eyes than men and more trouble with angle closure.

P:  Is open-angle or angle-closure glaucoma more common?

Dr. Rick Wilson:  Open-angle glaucoma is much more common than angle-closure glaucoma in our population.  Only about 15% of glaucomas are angle closure.  In China, however, the opposite is true, and angle-closure glaucoma is the most common cause of glaucoma.  Angle closure is very common in Eskimos and natives of Greenland.

P:  What is the difference between angle-closure glaucoma and acute-angle glaucoma?

Dr. Rick Wilson:  Angle closure can happen suddenly, as when pupils get wide in a dark movie theater or after ephedrine cold medication.  That causes severe pain, cloudy vision with colored rainbows around lights, and often nausea. Angle closure can also happen slowly over time without symptoms.  The latter may be true about two-thirds of the time, especially in patients of West African origin.  When angle closure happens quickly, it’s called acute-angle closure.

P:  What is the most common angle measurement?

Dr. Rick Wilson:  The most common angle measurement, when measured about a third of the way from the wall of the eye to the pupil, is 30 degrees.  It is often deeper in near-sighted people who have big eyes and shallower in far-sighted people who have small eyes.  Ten degrees is normal.  The angle is usually the narrowest at 12 o'clock.

P:  Should glaucoma patients ask their eye doctors what the size of their angles is?

Dr. Rick Wilson:  The real question is:  "Are my angles narrow enough to ever cause me difficulty?"

P:  How is the angle measured?

Dr. Rick Wilson:  The angle is measured using a "gonioscope," a lens that is often mirrored.  That allows the eye doctor to look into the angle of the eye.  The width of the angle usually is an approximate measure. Imaging instruments allow precise measurement of the angle, but that is rarely necessary.

P:  How many types of angle-closure glaucoma are there?

Dr. Rick Wilson:  The angle closure can be primary or secondary.  We discussed the primary type (when a small eye or an unusually formed anterior chamber allows the iris to get too close to the trabecular meshwork and get sucked onto the drain).

The angle closure also can be secondary to something behind the iris pushing it forward, such as fluid between the layers of the eye, a tumor, or swelling of the vascular middle coat of the eye, fluid accumulating in the back of the eye and pushing the iris forward, or the iris can be pulled over the trabecular meshwork by a vascular membrane (as is seen with diabetics and those who have had a stroke in the eye).

The iris can also be pulled over the drain by an abnormal corneal membrane, or an inflammatory membrane.  Inflammation can also glue the iris to the lens of the eye, which is right behind it, so that fluid cannot get into the front chamber of the eye. That pushes the iris forward, closing the drain.

P:  My angle-closure glaucoma is caused by ICE (irido-corneal syndrome). Is it my iris or my cornea that is the cause of the angle closure?

Dr. Rick Wilson:  It is your abnormal corneal membrane.  It is either covering the drain, preventing aqueous fluid from entering the drain, or the membrane may have pulled the iris over the drain and blocked it that way.

P:  What is plateau iris?  Does it make angle closure more likely?

Dr. Rick Wilson:  Yes. In plateau iris, the front of the eye (the space between the lens and iris and cornea) is moderately deep.  However, a high ridge or roll of the iris close to the drain makes the angle narrow and possible to occlude with the iris.

P:  What is the treatment for angle-closure glaucoma?

Dr. Rick Wilson:  The treatment varies according to the cause.  For primary angle closure, a hole made through the iris allows the fluid, which is produced behind the iris by the ciliary body, to enter the front of the eye without putting any forward pressure on the iris.  That lets the iris fall back away from the drain and open, if the drain has not been closed too long.

If the iris has been against the drain too long, it becomes scarred there and cannot be opened without surgery.  If the angle closure is secondary (that is, for a reason other than the anatomy of the eye), then that cause has to be attended to, whether it is fluid between the layers of the eye, a tumor, inflammation, the vascular membrane, etc. It becomes quite complex to try to list all the causes and the treatment for each.

P:  Are most traumatic glaucomas also angle-closure glaucomas?

Dr. Rick Wilson:  No.  Most may actually have a deeper angle in that the iris has been traumatically dislodged from its insertion into the inside wall of the eye and pushed backward.  The lens may also have been partially dislodged backward, making the front of the eye even deeper.

P:  Would you discuss the mechanics of chronic angle- closure glaucoma, where the angle is closed only intermittently?

Dr. Rick Wilson:  Eyes that may develop angle closure are difficult to predict unless the angle is very narrow.  If the angle is only intermittently closed and opens completely, it may be difficult to tell.  Usually after several episodes, however, the iris does not completely pull away from the drain, which is easily seen.

P:  Does an iridotomy cure primary angle closure?

Dr. Rick Wilson:  If the angle was never closed or only closed for a short time, then an iridotomy is curative in almost all people.  People with plateau iris are not helped much by an iridotomy and it may easily recur.

P:  Are glaucoma warnings on medicines more of a concern to patients with angle-closure glaucoma or with other types of glaucoma?

Dr. Rick Wilson:  The people who should be concerned don't know they are glaucoma suspects because of their narrow angles and ignore the warning.

Glaucoma warnings (steroids warnings are the main exception) are almost universally of concern for patients with narrow and occludable angles.  Unfortunately, most people with narrow angles don't know they are at risk unless they have had an eye exam and been told they are at risk.

Then they may well have had a laser iridotomy and don't have to worry about the warnings.  For the most part, the warnings are worthless and frighten people with open- angle glaucoma who shouldn't be concerned.

P:  Do steroid warnings apply to all glaucoma patients?

Dr. Rick Wilson:  Yes, in that it is difficult to tell if the patients are steroid responders without treating them with steroids and seeing if the IOP (intraocular pressure) increases.

P:  Why is there a difference in the prevalence of angle closure in different populations?  Is it related to the overall shape of the eye and the eye socket?  Is there a genetic component?

Dr. Rick Wilson:  It is certainly genetic in that the size of the eye and the shape of the iris are genetically determined.  Asian women in particular may have smaller eyes but also have iris shapes that put them more at risk.

Moderator:  Thank you for another informative chat, Dr. Wilson.

On February 7, Dr. Wilson discussed "What is the Trabectome?" in the Chat room. Click here for highlights of that meeting.

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