Small Incision Lenticule Extraction (SMILE) Eye Surgery Explainer

SMILE is a new approach to laser eye surgery that was approved by the FDA as recently as 2016. This operation benefits people with high levels of myopia, astigmatism, or both. It has lower rates of some side effects like dry eye compared to LASIK.

SMILE is not designed to help people with farsightedness, and it has a slightly higher risk of undercorrection compared to LASIK. Still, SMILE is very effective and might become more popular than LASIK soon.

What is SMILE?

Small incision lenticule extraction (SMILE) is a newer approach to refractive eye surgery, building on knowledge from years of LASIK and other laser eye surgeries.

Like LASIK, your eye surgeon will use guided lasers to change the shape of your cornea, so light refracts to your retina more efficiently, creating a clearer picture of the world. Unlike LASIK, lasers in the SMILE procedure form a disc in your cornea, called a lenticule, which is then removed to reshape the organ.

Currently, SMILE Is only effective for astigmatism, myopia (nearsightedness), or both. The U.S. Food and Drug Administration (FDA) has not approved this procedure for farsightedness, as the operation does not properly reshape the cornea to treat this condition. The procedure was approved recently, in 2016, and is growing in popularity compared to improvements in LASIK.

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Pros & Cons of SMILE

You may be familiar with LASIK as a surgery to correct a refractive error, but it may not be the best option for you. SMILE might work better to improve your vision.

Here are some of the benefits of SMILE compared to other refractive surgeries:

• Less direct impact on the cornea, leaving more tissue while improving visual acuity
• Uses femtosecond lasers for all stages of the process compared to traditional LASIK
• Does not create a flap in the cornea, reducing healing time

The major downside of SMILE is that it does not work for people with farsightedness. While there are improved healing times and visual acuity after the operation, people who have hyperopia or presbyopia currently do not have access to these benefits.

SMILE’s Success Rates

If you have a higher level of myopia, a significant astigmatism, or both conditions, SMILE might be a better option for you than LASIK. Although LASIK can improve vision for most people, SMILE might improve vision more significantly and for longer in people with higher order nearsightedness, especially when astigmatism also causes refractive errors.

A survey of SMILE metadata compared to LASIK found that both procedures worked well for people with myopia, astigmatism, or both. However, SMILE seemed superior in managing corneal sensation and improved eye watering after surgery, which reduces the risk of itching and dry eye.

SMILE was also found to be superior to LASIK in preserving the cornea after the surgery, so thin corneas would not cause later issues. Both procedures improved visual acuity to at least 20/40 in most recipients.

Another study of SMILE found that of 300 eyes with myopic astigmatism, 89 percent achieved 20/20 or better vision after the operation; 95 percent of the eyes were within 0.50 diopters of perfect vision, and none of the eyes lost visual acuity within the first year after the procedure.

You are eligible for SMILE if you:

• Are at least 22 years old, compared to 18 years old for LASIK.
• Have a stabilized refractive error that has not changed in the past year.
• Have nearsightedness between -1 and -10, and/or astigmatism up to 3 diopters.
• Have overall good eye health and are at low risk of corneal problems or eye infections.
• Have overall good physical health and are managing any chronic health conditions.

You are not a good candidate for SMILE if you:

• Have a changing refractive error.
• Have a skin condition, eye disease, or other condition that might affect healing, like diabetes or glaucoma.
• Have corneal abrasions, excessive scarring, or keloid formation.
• Have a history of eye disease or eye surgery, including LASIK.
• Are pregnant or nursing.

The SMILE Procedure

Before you undergo a SMILE procedure, you need to be examined by an ophthalmologist or eye surgeon to ensure your eyes are healthy and you are a good candidate for this procedure. This includes measuring your corneal thickness, taking your eye health history, examining your visual acuity, and examining your eyes for signs of other health problems.

The surgery itself takes between 10 and 15 minutes per eye, making it a shorter operation than LASIK. Steps in SMILE include:

• Programming a laser using measurements of the surface of your cornea.
• Receiving numbing eye drops.
• Placing an eyelid holder on your eyes so you do not blink during the operation.
• Having a small suction ring fitted on the surface of your cornea, which you will not feel except for a small amount of pressure.
• Having a laser form the lenticule underneath the suction ring.
• Having the lenticule removed through a minute corneal opening.

You will then be moved to a waiting area for up to 30 minutes to ensure the surgery has gone well. You should arrange for someone to drive you home after the operation.

Like LASIK, you can return to your normal work, school, and hobby activities in one to two days, although you should avoid strenuous exercise and getting water in your eyes for about a week after the procedure or until your eye surgeon clears you for these activities.

Recovery and Side Effects from SMILE

Since SMILE is a surgical procedure, there are side effects and potential complications, although these are very rare. These are some potential complications:

• Opaque bubble layer
• Subconjunctival hemorrhage
• Bleeding at the incision
• Black spots from trapped debris
• Remnants of corneal lenticule that are not removed
• Adhesions or lesions
• Tears around the incision from the suction device

The most common side effects of SMILE are like those of LASIK. They include the following:

• Dry eyes
• Corneal abrasions
• Infectious keratitis

Dry eye occurs in about 3 percent of patients and often clears up on its own in six months or less. Undercorrection is slightly more common in SMILE compared to LASIK, with 3 percent of patients receiving an enhancement procedure in about two years after their first SMILE operation. About 11 percent of people with astigmatism who choose SMILE have an undercorrection and need a second procedure.

References

1. What Is Small Incision Lenticule Extraction? (May 2021). American Academy of Ophthalmology (AAO).

2. Small Incision Lenticule Extraction. (July 2021). StatPearls.

3. Small Incision Lenticule Extraction (SMILE). (October 2021). EyeWiki, American Academy of Ophthalmology (AAO).

4. Small Incision Lenticule Extraction (SMILE): What Now? What Next? (August 2020). Ophthalmology.