Can LASIK treat astigmatism?
One of the most common questions patients ask me is if LASIK can treat astigmatism. The
answer is YES! And so can PRK and SMILE. In fact, laser eye surgery is often better than
contacts or glasses for treating astigmatism. Nonetheless, many patients still hold a stigma about
astigmatism. To understand why, let’s look at the meaning of the word astigmatism.
A Greek word salad with English dressing
Stigma is a Greek word meaning “point” or “a mark made by a pointed instrument.” The
figurative meaning – a mark of disgrace or infamy – developed in 17th century England as
criminals were often branded with pointed objects. Stigmata (the plural of stigma) holds a
theological significance for Christians as it refers to the wounds inflicted on Jesus’ body before
and during his crucifixion.
Linguistically, adding “a” before a word connotes “without.” Therefore, a-stigmatism means
“without a point.” Ergo, astigmatism is pointless!
The English polymath Rev. William Whewell (1794 – 1866) coined the term astigmatism to
describe a defect in an optical system in which light rays from a single point fail to converge in a
single focal point. So, when a single light ray passes through an eye with astigmatism, it is split
into multiple focal points, causing blurred vision.
Fun fact: Whewell also coined the terms scientist, physicist, and linguistics, among others.
Thanks, Will!
What causes astigmatism?
Most patients’ astigmatism comes from the shape of their cornea. The cornea is the clear
windshield of the eye and focuses light onto our retinas so we can see. If a cornea is perfectly
spherical (like a basketball), then it will bend any ray of light into a single focal point. If a cornea
is more football-shaped, then one axis of the cornea is steeper than the other. This causes light
rays to be bent differently depending on how they enter the eye. Therefore, the image generated
is blurry. The salient point here is that astigmatic corneas cause blurry vision.
How do I know if I have astigmatism?
Check out our previous blog post – How to Read Your Glasses Prescription – to learn how to
interpret all the numbers that your eye care provider records after measuring your prescription.
These numbers are called your refraction. If you’ve never worn contacts or glasses, you may
have uncorrected astigmatism if car headlights have the parallel, vertical streak lines like in this image. Want to get an updated refraction? We offer complimentary consultations and self-scheduling.
Why is my cornea shaped like a football?
Why are some corneas shaped like a football (or – for those nostalgic for the 1990s – like the
title character’s head from Hey Arnold!)?
The short answer is genetics. You can thank – or blame
– your parents for your eye shape. Your cornea is also affected by the shape and tension of your
eyelids, which press on your cornea with every blink. As our eyelids become droopier and looser
with age, so does their tension on the cornea. This causes a drift from a “horizontal football
shape,” i.e., with-the-rule-astigmatism, to a “vertical football shape,” i.e., against-the-rule
astigmatism.
How can you treat astigmatism?
So what can we do about all these Hey Arnold! eyes? There are four ways to treat any type of
refractive error, including nearsightedness, farsightedness, and astigmatism.
- Glasses: if you wear a lens of equal magnitude and opposite direction of your eye’s
astigmatism, the net result will be a spherical lens system focusing light onto a single
focal point. - Contacts: contacts work the same as glasses, but they sit on top of your cornea instead of
12-13 mm in front. Astigmatism-correcting contacts are called “toric” lenses, and they
are weighted so that the contact aligns with the axis of astigmatism. Toric lenses can
jostle and rotate with blinking or tears, which causes blurry vision. - Laser vision correction: SMILE, LASIK, and PRK each accomplish the same task. They
reshape the cornea so it bends light to land perfectly on the retina, allowing for clear
vision. - Lens-based surgery: Many patients who do not qualify for laser eye surgery opt to have
an artificial lens (ICL) placed inside their eye to counteract their astigmatism. Patients
who undergo cataract surgery also receive an artificial lens placement, which can correct
for refractive error.
Laser vision correction is the only option that corrects astigmatism (and other refractive errors)
DIRECTLY by giving patients spherical corneas. Conversely, contacts, glasses, and lens-based
surgeries do not treat the underlying cause of astigmatism; they merely counteract its effects.
Many patients with astigmatism enjoy better vision after laser eye surgery compared to their
vision corrected by contacts and glasses for this very reason.
LASIK: turning footballs into basketballs since Y2K.
Why do so many patients keep asking about LASIK’s ability to treat astigmatism? The short
answer is that excimer lasers received FDA approval for treating myopia (nearsightedness) in 1998. Astigmatism correction was approved in 2000. This was over two decades ago, but old tropes die hard. Although there are several reasons someone may not be an excellent candidate for laser eye surgery – such as severe dry eye, glaucoma, or pregnancy – astigmatism is not one of them.
Conclusion
We’ve learned that astigmatism is pointless linguistically but pertinent optically; that, without
correcting for astigmatism, images are never in focus; and that, while contacts and glasses
counteract the effects of corneal astigmatism, laser eye surgery like SMILE, LASIK, and PRK
fix astigmatism permanently by treating the root cause. Want to learn more? Follow us
@corsinilasereye or schedule a complimentary consultation to have all your eye care
questions answered. Thanks for reading!
Cheers,
Jonathan Corsini, MD