Joel Hunter, MD Refractive Surgeon, Hunter Vision Updated 02/07/18 8:15 AM
Astigmatism can be overcome with glasses or contacts. It can be cured by refractive surgery. The difference there isn’t just semantics. In the first case, you’re neutralizing the blur from astigmatism. In the second, you’re getting rid of the cause of astigmatism. In the words of the old, solemn proverb: “Don’t start none, won’t be none.”
What is astigmatism?
Astigmatism is caused by a “squished” shape to your eye’s lens (either the cornea or crystalline lens inside). It should be round. Imagine a perfectly clear glass sphere that just creates a tiny image of whatever you view through it. Then mentally heat it up and let it get smooshed into a perfectly clear glass oval, like the shape of an Advil Liquigel. Do you see in your mind’s eye looking through that oval how everything you see gets squished and distorted? That’s astigmatism.
With glasses and contacts, the blur (the “squish” distortion) created by astigmatism is matched exactly with an opposite amount of astigmatism so that the image is clear by the time it is projected onto your retina. If your eyes’ lenses squish an image by x amount, then your glasses will squish the image by that same x amount but in the opposite direction. It really does work to fix the blur! I think that’s neat. More importantly, it makes glasses and contacts extremely helpful to people with astigmatism.
How can refractive surgery help?
In refractive surgery, the object is to fix the actual cause of the blur. It is to “unsquish” (sorry, I realize I’m playing fast and loose with the amount of made up words you’ll tolerate) the lens and make it round again. There are two main ways to do this, and both involve the cornea. As a quick aside, you may have seen that astigmatism can come from the crystalline lens inside the eye, as we sometimes see in cataracts. No worries when that happens, because removal of the cataract gets rid of the astigmatism and the new intra-ocular lens is astigmatism-free.
The cornea can either be sculpted into a round shape or relaxed into a round shape. For sculpting, LASIK works beautifully. I’ve written elsewhere about LASIK for astigmatism and how well it works with modern laser. That’s still true. For the other option, relaxing the cornea into a round shape, the method is different. A type of laser called a femtosecond laser can create small incisions at a very exact depth where the corneal curve is a little too tight. Cutting a few — but emphatically not all — of those corneal fibers relaxes the astigmatism away. This is called a limbal relaxing incision or LRI for short. An LRI is kind of similar to cutting a few stitches on a dress that is binding too tight somewhere. Maybe. I don’t know, I’m not a dress maker.
To get rid of the blur of astigmatism you can wear glasses or contacts, and if you’re happy with them, you may not need to look further into it. For some folks, however, glasses and contacts don’t work or they’re just annoying. In those cases, refractive surgery may be able to cure the astigmatism altogether. And with the cause of the blur removed, the vision can be clear without having to use any correction at all.