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There are two main types of glaucoma, open-angle and angle-closure, each with very different attributes. This article discusses angle-closure suspects.
We now say someone has glaucoma when there is structural injury to their optic nerve inside the eye or functional damage measured in their visual field test. Angle-closure is less common than open-angle glaucoma, but causes more vision loss for those who have it if it is not treated properly. Suspects for angle-closure glaucoma have different factors that identify them compared to open-angle suspects.
Angle-closure disease happens when the colored part of the eye (iris) blocks water movement out of the eye, raising eye pressure (IOP). This can happen either suddenly and painfully in an acute angle-closure attack, or more commonly, angle-closure develops gradually and silently.
The iris is more likely to block outflow in smaller eyes, since things are more crowded together to start with. The eye doctor can estimate how likely this would be using a detailed exam called gonioscopy. While many eyes have narrow angles by gonioscopy, only a small percent of these will ultimately get angle-closure disease. There are 10 to 20 angle-closure suspects for every person that gets the disease.
The definitive treatment for angle-closure glaucoma is to prevent iris blocking of outflow by making a laser hole in the iris— iridotomy. We could perform iridotomy on every angle-closure suspect, but that would treat several persons needlessly. Instead, eye doctors attempt to estimate the risk of angle-closure development by evaluating a series of other risk factors.
Older persons are more likely to develop angle-closure glaucoma, peaking around age 60, possibly since the angle gets more crowded with age.
Angle-closure affects women 50% more often than men. The reasons for this aren’t known, but women do have smaller eyes.
Asian and Indian persons have much more angle-closure glaucoma than everyone else in the world for reasons that are not yet clear.
Family members of those with angle-closure glaucoma are 10 times more likely to develop it, so presently unknown genes must play some role.
Smaller eyes are often “far-sighted”, so persons with hyperopia are more likely to get angle-closure.
Factors increasing angle-closure risk:
Currently, there is no definitive way to predict which angle-closure suspect will develop angle-closure disease but this is an area of active research. Recently, imaging instruments permit painless and inexpensive measurements of the eye structures that are crucial to developing angle-closure glaucoma. These add to the exam done by the doctor and have begun to provide more data about who is most likely to get angle-closure glaucoma and therefore who should have laser iridotomy.
Interestingly, it is not so much how crowded or narrow the passages are that is being linked to angle-closure glaucoma, but how the structures in the eye act in real time. How the iris changes in size and position is proving to explain more about this disease.
Further studies have linked swelling inside the back of the eye in its choroid to angle-closure glaucoma, as well.
The standard exam findings and other personal factors of each angle-closure suspect are taken into account by the doctor in presenting the risk and benefit of preventive laser iridotomy.
Article by Harry A. Quigley, MD. Dr. Qigley is the A. Edward Maumenee Professor and Director of the Glaucoma Center of Excellence at the Wilmer Eye Institute at Johns Hopkins, in Baltimore, Maryland. He has participated in glaucoma studies worldwide and published over 350 peer-reviewed articles.
Last reviewed on September 15, 2015
This article appeared in the January 2014 issue of Gleams.Subscribe