What is Narrow Angle Glaucoma? What is Acute Angle Closure?
Good morning! I am Dr. David Richardson, I’m a cataract and glaucoma surgeon in Southern California. Today I’d like to talk a bit about narrow angle glaucoma.
So let’s get going!
So, here in the United States, narrow angle glaucoma is actually or has actually been in the past relatively unlikely. So, most glaucoma in the US is what we call Open Angle glaucoma.
Narrow angle glaucoma, in which the angle—which is the angle between the underside of the cornea and the top side of the iris, is narrow… Now, the reason why narrow angles versus open angles is an important distinction is the trabecular meshwork. That’s the drainage grate in the eye and I use that term with the knowledge that it’s far more than just a drainage grate but for ease of discussion it’s where fluid drains out of the eye. Now, if that space—just on the side of that grate (the trabecular meshwork), is narrow, it restricts flow. Whereas if it’s a nice open angle rather than a narrow angle the flow then is not physically restricted at least to the trabecular meshwork.
Now, in open angle glaucoma, the problem is actually at the trabecular meshwork. So, the fluid can get to the trabecular meshwork just fine but it can’t get through the trabecular meshwork. In narrow angle anatomy, however, the problem is even getting to the trabecular meshwork. If the angle narrows sufficiently then it can actually be what’s called “closed”. Now, narrow angles and closed angle, both we call, “chronic angle closure” as well as “acute angle closure”— so chronic, “over a long term”; acute, “over a very short term”. Narrow angle glaucoma tends to be far more common among Asians—so in Asian countries, such as China, it’s actually the most common form, whereas, traditionally, here in the US, it’s been far less likely to encounter narrow angles. That is changing as their demographics change.
So what’s important to know, is that with narrow-angle anatomy you can have pretty severe fluctuations in the pressure, which are not necessarily symptomatic. So, the individual with narrow angles may not even know, it, which over time can result to damage the optic nerve. Now, this can be relatively difficult to catch unless someone has seen an ophthalmologist on a regular basis and having the angles actually evaluated either at the slit-lamp-that’s the exam microscope with an exam called Gonioscopy or with a type of scan called (OCT) Optical Coherence Tomography.
Now, those who have (chronic) chronically narrow angles are at risk for loss of vision but what we worry about, in general, the most is what’s called an “acute angle closure”. Now, an acute angle closure is when the angle narrows so much that it closes off and once it’s closed off there’s no there’s no feedback loop, there’s nothing telling the ciliary body , which produces fluid, to stop producing fluid because the fluid can’t get out so the fluid just keeps getting produced, building up in the eye, it can’t get out, which further closes off the angle and you can end up with a very high elevation of pressure, in a very short period of time. Then in a matter of hours the pressure can go off into the 50s 60s 70s (mmHg). It’s been measured as high as the 80s. The normal is generally below 20 (mmHg). Now, when you get above 50 (mmHg) you actually the pressure in the eye is so high it can actually cut off the blood supply you can stroke out the tissue in the eye. So, an acute attack of angle closure is a medical emergency because the vision can be lost permanently in a matter of a very short period of time hours.
So what are the symptoms…because unlike chronic angle closure which can be symptom-free an acute attack of angle closure tends to be symptomatic that the symptoms are not always obvious. So, obvious symptoms would be blurred vision or a red eye or painful eye…you know, those are those are things that you should know, “ah, something’s wrong here…” But there are more subtle symptoms that may not be associated with obvious loss of vision or pain. So, other symptoms include such things as seeing rainbows around lights as one or just a headache or nausea or even vomiting. So, you could have nausea and vomiting without eye pain. So there have actually been people who’ve gone to the emergency room for nausea/vomiting, worked out for stomach issues, and what was really going on was angle closure. So, that’s why it’s important to know your anatomy so that if you have any of these symptoms, if you’re at risk for angle closure, you know what to look out for.
Now, for those who have an acute attack of angle closure the treatment is generally an in-office laser treatment. Although sometimes it does require going to the operating room in order to make a hole in the iris so that fluid can get from behind the iris into the angle and then out the trabecular meshwork into the Schlemm’s canal and out through the collector channel system.
Now, if it’s not treated right away or there’s been chronic angle closure in addition to acute then sometimes the iris can actually scar down to the trabecular meshwork and even with creating that opening in the iris it may not be enough, in which case other surgeries may be necessary. Another thing to keep in mind is that we’re now discovering the removal of the natural lens, which tends to push up against the iris and narrow that angle—removal of the natural lens itself can be a very effective treatment for narrow angle anatomy. And so for those with narrow angles we are now, moving early and earlier toward removing cataracts even when the vision may not be at the level where we would normally consider cataract surgery.
So, one of the things that an individual can do in order to avoid or reduce the risk of angle closure (acute angle closure) is to have the anatomy checked out in an ophthalmologists office and if the angle is already narrow, to go ahead with the laser procedure, which is called, “laser peripheral iridotomy “ in order to prevent closure. It’s not a hundred percent prevention but it does a good job of preventing it in the majority of those who have narrow angles.
One other thing I’d like to point out for those who have narrow angles they really should avoid over-the-counter cold allergy sinus or anti-nausea seasick medications because most of those medications tend to further narrow the angle placing someone at risk of developing angle closure. So, fortunately most of these medications now, have warnings on them that say if you have narrow-angle do not take, but in general just try to avoid those if you have narrow angles especially if you’ve not yet had prophylactic preventative laser peripherally iridotomy performed on your eyes.
If you have had laser peripherally iridotomy, depending on how the angle anatomy changes after the laser, you may be okay to take those over-the-counter medications but again that would be something that would need to be assessed by your ophthalmologist either at the slit lamp or with OCT and if sufficient opening has occurred after the laser then it may be okay to go back to some of those medications. I know, for those who have bad allergies and a bad cold and right Now, we’re in the cold flu season that’s not what you want to hear, it’s miserable enough having any of these things without not being able to treat them but the risk of a permanent loss of vision is just too high, if you are at high risk.
So, anyway there’s a lot more that I could say about narrow angles both chronic and an acute but I think that’s a good place to end today alright have a great day and I’ll be chatting again soon
Don’t delay getting checked for glaucoma.
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