Understanding primary angle closure glaucoma

September 19, 2015

Glaucoma comes in more than one flavor, and while open-angle glaucoma has received more attention, its angle-closure cousin has flown under the radar in the United States.

Las Vegas-Glaucoma is a major problem among the aging population. With more than 3 million Americans diagnosed with the disease and rising rates each year, the disease is has become a primary concern among optometrists and ophthalmologists nationwide. But glaucoma comes in more than one flavor, and while open-angle glaucoma has received more attention, its angle-closure cousin has flown under the radar in the United States.

"Some 85 percent of all angle-closure glaucoma is on the Asian subcontinent, so that thought process of, 'It's not really a North American problem,' is true," says Andrew Mick, OD, FAAO, of the San Francisco VA Medical Center Eye Clinic at a recent lecture at Vision Expo West 2015. "But then, it assumes it's not a large percentage here. It's a huge concern in Asia-it's actually a huge concern anywhere where it's found because angle-closure glaucoma blinds people at five times the rate of open-angle glaucoma.

 

Angle closure across ethnicities

Even in a group where practitioners tend not to think about angle closure-Caucasians-it's found in 3.8 percent, he said, citing a 1980 Framingham study that looked at Caucasians over the age of 55.

"Now, that’s not a big percentage, but man, as I often say, think about some of the other conditions you're heard about in other lectures that are rarer,” Dr. Mick says. He point out that this this is one of the lowest rates among population. "If you have Asian Americans in your practice, the rates are astonishing."

Studies have found rates as high as 24 percent among Filipino Americans with a mean age of 60; 47.8 percent among 55 or older Vietnamese Americans; and 60.2 percent among Chinese Americans with a mean age of 66 for women and 69 for men.

Next: The language of angle closure

 

The language of angle closure

With angle closure glaucoma much more prevalent than most suspect, it's important that ophthalmologists begin adopting a common language to better identify and understand this disease.

"There's been a push in the literature in the past, I would say six to seven years, to really define these exacting definitions so that when you see a patient, you can classify them,  and when you read a paper, you understand what they mean with these particular terms," Dr. Mick said.

The main terms to come out of this effort are primary angle closure suspects (PACS), primary angle closure (PAC), and primary angle closure glaucoma (PACG).

 

Defining angle closure terminology

Primary angle closure suspects (PACS). Patients with occludable angles with less than 90 degrees of posterior pigmented trabecular meshwork (TM) visible without indentation. Also characterized by no peripheral anterior synechiae, or elevated intraocular pressure (IOP) (below 21).

Primary angle closure (PAC). Patients with occludable angles with less than 90 degrees of posterior pigmented TM visible without indentation. Patient has either peripheral anterior synechiae or elevated IOP-or both-but still has a normal visual field and optic nerve.

Primary angle closure glaucoma (PACG). Patient has primary angle closure with glaucomatous optic neuropathy.

Dr. Mick points out that these definitions do not rely on the reason why the closure is happening, which can be due to one of many causes. The primary mechanistic causes include pupillary block, plateau iris configurations, and phacomorphic glaucoma.

Knowing these definitions is just the start of the process needed to help bring more awareness to angle closure glaucoma. With so many people suffering from the disease, and many more who might not be symptomatic but are at risk-and in fact, the majority of those at risk show no symptoms-the U.S. medical establishment must take greater notice, Dr. Mick says. Angle closure needs to stop being the "other" glaucoma because it's too dangerous and prevalent to ignore.

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