Last week, I wrote about all the different options for a patient who is told they’re not a candidate for LASIK. This week, I’d like to dive deeper into the decision tree that underlies my recommendation for one option versus another.


If you have a significantly thin or irregular cornea, you may not be a candidate for laser eye surgery. Luckily, you may still be a candidate for ICL or RLE (discussed last week). Alternatively, you may remain in contacts or glasses.

For corneas that are only slightly thin or irregular – a “yellow flag” instead of a “red flag” – then PRK is likely your best bet. Less corneal tissue is altered in PRK, which can be safer for patients with yellow flags on their pre-surgery scans.

I underwent PRK in the Air Force because I had a few “yellow flags” that would have made SMILE or LASIK a riskier option for me. Though the recovery is longer in PRK, the final vision is the same as with other surgical options.

Most patients have relatively normal corneas, which qualifies them for either SMILE or LASIK.


Refractive error describes imperfection in the way that your eye bends light to bring images into focus on your retina. You can liken your cornea and lens to the lens of a camera and your retina to the film of a camera. The job of your cornea and lens is to bend light perfectly so images land clearly on your retina.

Most patients have some refractive error. If you are myopic (nearsighted), your eye focuses images in front of your retina. If you are hyperopic (farsighted), images come into focus behind your eye. In both cases, the image is out of focus when it crosses your retina, causing blurry vision.

Astigmatism means that your eye bends light differently depending on which axis of your eye the light passes through. Both hyperopic and myopic eyes can have astigmatism. What about an eye that has one farsighted axis and one nearsighted axis? That is called mixed astigmatism.

LASIK is the best option for patients with normal corneas that are hyperopic or have mixed astigmatism because SMILE is not FDA-approved to treat these conditions. For normal myopic corneas, we move on to the final question.


LASIK has slightly better outcomes than SMILE for patients with large amounts of astigmatism – usually 2.50 diopters and above. For patients with corneas that have between 1.75 and 2.25 diopters of astigmatism, I will discuss the relative benefits of each procedure and make my recommendation on a case-by-case basis. But, generally speaking, I recommend SMILE for all patients with normal corneas and less than 2.50 diopters of astigmatism.

Why? As amazing as LASIK is, SMILE is flap-free, leading to less postoperative dry eye and a quicker return to normal activities. And, although flap dislocation is very rare after LASIK, it’s not an issue at all with SMILE.


·      Nearsighted with no, low, or moderate astigmatism? SMILE it is!

·      Farsighted, mixed astigmatism, or high cylinder? LASIK is the way to go.

·      Slightly thin or irregular cornea without red flags? PRK all the way.

·      Abnormal cornea? ICL or RLE might be right for you.


This treatment decision tree is generalized. I always consider each patient’s entire story, which may lead me to a different recommendation than the above algorithm. Some special considerations include:

·      Have dry eyes? PRK or SMILE may be better as they have less postoperative dry eye than LASIK.

·      Need a quick return to normal activities? LASIK or SMILE recover much quicker than PRK, needing only 24 hours before you can get back to work.

·      Love contact sports? SMILE may be the better option since there is no risk of traumatic flap dislocation.

·      Have corneal scars? PRK may be safer as the scars can interfere with the laser that performs SMILE and creates the LASIK flap.

·      Have significant haloes or glare? Topography-guided LASIK (Contoura) may be your best option to minimize these symptoms after surgery.

Now you know what goes on inside an ophthalmologist’s head when they are evaluating you for surgery! Want to discover which option is best for you? Schedule your free, no-hassle consultation or call to learn more.

Thanks for reading!

Jonathan Corsini, MD