Can LASIK Fix Astigmatism?
The short answer: Yes, LASIK can fix astigmatism, and we have been doing so since the previous millennium. OK yes, that sounds like a lot, but it has been nearly 25 years of correcting astigmatism with LASIK and PRK. This question from patients always reminds me that if people have heard of the word astigmatism, they still have no idea what it means. My job in this blog post is to explain it to you. I hope you learn something in the next five minutes as you read this.
What is Astigmatism?
Picture in your mind a tennis ball. It’s perfectly round. Now cut that tennis ball in half with a kitchen knife-be careful, even if it’s in your imagination! Now take the edges of that half tennis ball between your thumb and middle finger. As you squeeze the edges of that tennis ball closer together, you are creating the shape of astigmatism. The tennis ball becomes less perfectly round as you squeeze. The more you squeeze, the more astigmatism you are making.
Another commonly used analogy is a football. A football obviously is not round. The curvature from end to end of a football is less curved than the curvature perpendicular to the length of the football. I like this analogy also. It fits the shape of astigmatism.
Our eyeballs are similar to this tennis ball shape, so those with astigmatism alone will have distorted vision. It’s maybe a bit harder to explain the vision with astigmatism, but it’s as though lines are clear, but you still can’t read signs. The vast majority of people with glasses will have astigmatism in combination with nearsightedness or farsightedness. This is why you may not realize you have astigmatism, but more than 90% of our patients who come to us for LASIK or PRK also have astigmatism.
Is it Abnormal to Have Astigmatism?
Astigmatism is often described as “regular“ or “irregular“ astigmatism. This is perhaps getting too academic, but 99% of the astigmatism is pretty regular. There are pathologic conditions of the eyeballs that indicate an irregular astigmatism where there is a bulge or weakness in the structure of the cornea. This is why every single patient we see at SharpeVision Modern LASIK gets a comprehensive exam prior to recommending a procedure. We must make sure that your eyeballs are completely healthy (except for the nearsightedness, astigmatism, farsightedness). We must scan your eyeballs with several different instruments to determine the curvature of the front and the back of your eye, the thickness, symmetry, and several other important factors. If we find irregular astigmatism, we will discuss this with you and determine which procedure would be best- even if that is no procedure.
Keratoconus is a type of irregular astigmatism that indicates a weak area of your cornea and is a contraindication to having LASIK. This irregularity can be diagnosed with corneal topography, which we perform on every patient. Keratoconus will be discussed in a blog post coming soon.
Can LASIK Fix Astigmatism?
We have been correcting astigmatism for our patients since 1997. The first laser for correcting nearsightedness was approved by the FDA in the USA in October 1995. It was originally approved for PRK only, and only if you didn’t have astigmatism, so that most people were not candidates for laser vision correction in 1995. The approval to correct astigmatism with the laser came (fortunately) just two years later in 1997. Since 1997, the lasers have gradually improved to make the treatment of astigmatism better and better. I’d list the important improvements in LASIK and PRK (in historical order) as:
- Infrared eye tracking: This is an amazing technology that appeared on all lasers in the very early 2000s. This means that if your eye moves during treatment, the laser follows and follows faster than any surgeon could react. If your eye moves too far or too fast for the laser to follow, the laser stops instantly. Pretty cool and reassuring to patients (and surgeons) that they aren’t going to “mess it up” if they move. Infrared eye tracking uses the heat from your iris, the colored part of your eye, that has blood vessels running through it. The iris is warmer than your pupil, the circular black opening in the iris. Infrared eye tracking allows extremely precise treatment of astigmatism and nearsightedness, so that the treatment is placed exactly where it needs to be to fix astigmatism.
- Better treatment profiles: By “better treatment profiles“ I mean that the pattern/shape that the laser uses to correct your astigmatism and nearsightedness is more optically beneficial. Less aberration, therefore less glare and halos. There will always be some degree of glare/haloes after LASIK and PRK fixes your astigmatism and nearsightedness, but it’s usually the same or better than you’d see with contacts or glasses. Current laser treatments incorporate larger treatment zones, increased blending, and gradually transitioning to the edges of your cornea. This has occurred gradually over the 2000-2015 timeframe.
- Femtosecond lasers: Femtosecond lasers have not changed the fact that we can and do treat astigmatism and nearsightedness with the Excimer lasers. In case you weren’t aware, we use two highly different and precise amazing laser technologies to perform LASIK surgery. First is the femtosecond laser, which has replaced the blades used to create the LASIK flap in the early 2000s. The femtosecond laser allows us an inconceivably precise creation of the laser flap. It is consistent, thinner than the bladed flap, can be precisely placed over the pupil, and can create side cuts to allow a “manhole cover“ shape of the flap, so that the edges are vertical, more stable, and less prone to epithelial in-growth. The femtosecond laser was first approved in 2001, but there have been many improvements in the speed, quality, and precision as well as programmable shapes, and sizes which make LASIK easier, safer, and more predictable to correct astigmatism and nearsightedness.
- Wavefront guided or topography guided laser ablation treatment profiles: Wavefront guided and topography guided in my opinion are just different names for the same thing. My laser uses topography guided, but in fact it incorporates all aspects of the wavefront, topography, and nearsightedness/astigmatism of each individual eyeball to generate a perfect and completely customized and unique treatment for any specific eye. LASIK fixes regular astigmatism as described above, but each of us has some degree of irregularity that generally does not affect vision significantly and is most of the time 2% to 5% of the overall aberration of our eyeball. Wavefront guided lasers are designed to correct these slight imperfections to perhaps create slightly better night vision and quality of vision.
Exactly How Does the LASIK Laser Fix the Astigmatism?
Ok, I’ll make an attempt to create a mental picture of exactly how LASIK fixes astigmatism with the excimer laser. Imagine that same football described above is made of clay. The laser is like a knife that scrapes away an increasingly larger circle of that “clay” -or tissue- to fix nearsightedness. The laser scrapes away an increasingly larger ellipse (oval) to fix astigmatism. The elliptical shape would be longer along the long end of a football, so that the eyeball would be perfectly spherical (round) after fixing astigmatism. To fix nearsightedness, the laser is flattening the curve of the front of our eyes to decrease the focusing power of our eyes. To give you an idea how precise the laser is, it would take exactly 4000 laser pulses to remove a single millimeter of corneal tissue. The laser is programmed based on all the scans, measurements, and irregularities of your unique eyeball.
LASIK and PRK use the same laser to correct astigmatism and nearsightedness with extreme precision. LASIK and PRK have been used to fix astigmatism since 1997. If you still think you’re not able to have clear uncorrected vision, I implore you to see us. The exam is free and comprehensive. Schedule your exam either online at sharpe-vision.com or call us at 425-451-2020. Why are you waiting another day to get clear vision and ditch those glasses and contacts?