Plateau Iris Syndrome
Chat Highlights
May 6, 2009

On Wednesday, May 6, 2009, Dr. Michael Pro, a glaucoma specialist at Wills, and the glaucoma chat group discussed "Plateau Iris Syndrome".

Moderator: Welcome everyone. Tonight's topic is “Plateau Iris Syndrome.” First of all, Dr. Pro, can you tell us what it is?

Dr. Pro: Let's have a quick introduction. I invite chatters to visit eMedicine to read the excellent overview on Plateau Iris by Drs. Wang, Ritch, and Tello.

(http://emedicine.medscape.com/article/1207281-overview). I am personally indebted to Drs. Ritch and Tello as they were my mentors in my own Fellowship. They have authored numerous articles about this condition and Dr. Ritch helped to develop the laser treatment for this condition.

Plateau Iris syndrome is defined as a persistently narrow angle in spite of a patent iridotomy. It is further defied as specific findings on gonioscopy (evaluation of the angle) during examination.

P: How is it different from regular narrow angles?

Dr. Pro: Well, in most patients with routine narrow angles, performing the iridotomy opens up the angle. In Plateau Iris, the angle remains occludable with a patent iridotomy. Also, the examiner will find the classic "double hump" sign on gonioscopy. This is due to anteriorly positioned ciliary processes, which hold the peripheral iris forward.

From the eMedicine article mentioned above: “The more peripheral hump is determined by the ciliary body propping up the iris root, and the more central hump represents the central third of the iris resting over the anterior lens surface. The space between the humps represents the space between the ciliary processes and the endpoint of contact of the iris to the anterior lens capsule.”

Moderator: What is a patent iridotomy as distinct from a regular iridotomy?

Dr. Pro: “Patent" just means "open."

P: What is the difference between Plateau Iris syndrome and Plateau Iris configuration?

Dr. Pro: The configuration is the finding on gonioscopy that I quoted above, the syndrome refers to the above finding as well as an occludable angle in spite of an iridotomy. This syndrome can lead to chronic angle closure glaucoma.

P: Is it hereditary?

Dr. Pro: It is thought to have a genetic component, but we don't really know all the genes involved. In general it is more common in patients who have a family history of angle closure.

P: I asked about heredity because my mother, aunt and brother all have had iridotomies and I wonder if they also have Plateau Iris.

Dr. Pro: Well, just like other features in the body (hair color, etc.), the shape of the eye is influenced by your genes. In the case of your family, most people with narrow angles do not have Plateau Iris, but you may want to inquire of your physician.

P: Why do some patients have Plateau Iris syndrome diagnosed before an iridotomy, and others receive their diagnosis after?

Dr. Pro: Well, I think that Plateau Iris syndrome is not always clear-cut. There are a few patients who just have the classic gonioscopic findings as above, but many patients are somewhere in between. In general the first step in treatment for a narrow angle is an iridotomy, and if the angle is still narrow then you think about Plateau Iris.

P: Of all patients with glaucoma, what percentage suffer from Plateau Iris syndrome?

Dr. Pro: Some articles suggest that as many as 50 percent of patients with narrow angles have some degree of Plateau Iris, but that is probably a gross overestimation. So we need to divide the total: In the U.S. the majority of patients have open angle glaucoma (about 80 percent, I believe, but I may need to check that) which would mean that about 20 percent have angle closure glaucoma. Perhaps half of the angle closure glaucoma in patients may be due to Plateau Iris (as distinct from narrow angles, which does not always cause glaucoma). Thus up to 10 percent of glaucoma in the U.S may be from Plateau Iris. In Asia, where angle closure glaucoma is more common, the significance of Plateau Iris is thought to be greater.

P: If Plateau Iris syndrome is (partially) defined as the angle still being occludable after an iridotomy, then how it is treated?

Dr. Pro: Argon laser peripheral iridoplasty (ALPI) is a procedure that consists of placing large laser burns on the peripheral iris, which compacts the iris down and draws it away from the trabecular meshwork.

P: Is this a new procedure?

Dr. Pro: This is the procedure of choice, and it not new. In fact, Dr. Ritch helped develop it over 20 years ago.

There are adverse effects from any procedure, and the ALPI is no exception. These may include a dilated pupil, photophobia, inflammation, and the effect of the procedure may wear off over time. Also, cataract surgery is as effective, if not more effective, at opening the angle in this condition.

I will admit that I perform many fewer ALPIs than some other doctors. I guess that is because I am often sent patients who already have glaucoma and I am called to perform trabeculectomies or other surgeries. Plateau Iris is also one of those conditions which some doctors may diagnose more often because they are looking for it.

P: At what pressure do you do an iridoplasty, and what is the target pressure after it's done?

Dr. Pro: It is not really about target pressure, just as doing an iridotomy is not about a target pressure. It is about trying to keep the angle open and about preventing the development of chronic angle closure glaucoma.

P: Is Plateau Iris syndrome more prone to angle closure? I ask because I have been diagnosed with Plateau Iris but haven't had any angle closure attacks and neither have my mother, aunt, or brother.

Dr. Pro: Angle closure attacks are rare, and I do not think that they are more common in people with Plateau Iris than in persons with relative pupillary block narrow angles.

P: Can an eye with Plateau Iris be dilated?

Dr. Pro: If the angle is still narrow, then there is a risk of an angle closure attack, even with an open iridotomy.

P: What is ultrasound biomicroscopy (UBM), and is it done just once or can it be repeated?

Dr. Pro: The UBM is a device that can image the ciliary body and it is used to confirm the diagnosis of Plateau Iris. Like most imaging technology, it can be repeated again and again. Usually you would do it once to confirm the diagnosis and perhaps again after laser treatment was performed to see if the angle configuration was improved. The UBM is a form of ultrasound.

P: Is an ALPI more painful than ALT used for open angle glaucoma patients?

Dr. Pro: Yes, it is more painful.

P: Do you recommend repeating ALPI if the effects wear off?

Dr. Pro: I usually do not repeat it; cataract surgery can often help.(If there is a cataract.)

P: Dr. Pro, is one sex more effected by plateau iris?

Dr. Pro: Yes, women are more effected, usually those from 30 to 50 years of age and farsighted.

P: What other conditions can be confused with Plateau Iris syndrome?

Dr. Pro: Phacomorphic angle narrowing, when the cataract is so large that it crowds the iris forward, can be confused with Plateau Iris syndrome.

P: What medication is generally prescribed and why?

Dr. Pro: Pilocarpine may help to open the angle in some patients. It may thin the iris stroma and pull the iris away from the trabecular meshwork.

P: If diagnosed in a young woman, what occurs during pregnancy/breastfeeding as far as medications?

Dr. Pro: Plateau Iris in a young woman would usually be treated with lasers. Although pilocarpine has been safely used during pregnancy, like all glaucoma drugs, it was not specifically studied in pregnancy.

P: Does a trab do anything for plateau iris?

Dr. Pro: A trab is almost always done in cases of open angle glaucoma or chronic angle glaucoma where medications or lasers have failed to control the glaucoma and there is either a worry that the visual field will worsen or the field has been getting worse.
Moderator

Moderator: Thank you for joining us this evening. It's always a pleasure.

Dr. Pro: You are welcome. Great questions tonight; what a smart group! Good night.

On May 18, Dr. Pro discussed "Rescue of Failing Blebs" in the Chat room. Click here for highlights of that meeting.

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