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What Is SMILE Laser Eye Surgery?

SMILE, which stands for Small Incision Lenticule Extraction, is the newest generation of laser vision correction. While LASIK is famous for creating a large corneal flap (like opening the cover of a book), SMILE is a minimally invasive procedure that leaves the surface of the eye largely intact. Often described as "keyhole" surgery, it uses a single laser to perform the entire correction through a tiny incision less than 4 millimeters wide. This structural preservation appeals to patients involved in contact sports or professions where the risk of flap dislocation is a concern.

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What Is SMILE Laser Eye Surgery?

SMILE, which stands for Small Incision Lenticule Extraction, is the newest generation of laser vision correction. While LASIK is famous for creating a large corneal flap (like opening the cover of a book), SMILE is a minimally invasive procedure that leaves the surface of the eye largely intact. Often described as "keyhole" surgery, it uses a single laser to perform the entire correction through a tiny incision less than 4 millimeters wide. This structural preservation appeals to patients involved in contact sports or professions where the risk of flap dislocation is a concern.

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How It Works (The Lenticule)

The procedure relies exclusively on a femtosecond laser, such as the Zeiss VisuMax. Unlike LASIK, which uses an excimer laser to burn away tissue, the SMILE laser carves a microscopic disc of tissue, called a lenticule, inside the middle layer of the cornea. The laser creates this disc and simultaneously makes a small tunnel incision on the surface. The surgeon then reaches through the tunnel with a specialized instrument and gently pulls the lenticule out. Removing this disc flattens the shape of the cornea, correcting the refractive error.

The Dry Eye Advantage

One of the most significant clinical benefits of SMILE is its impact on corneal nerves. In a standard LASIK procedure, the creation of the flap severs the nerves across a large circumference (roughly 20mm), which often leads to temporary or chronic dry eye syndrome because the eye loses the sensation to produce tears. Because the SMILE incision is so small (2-4mm), the vast majority of the anterior corneal nerves are left untouched. Studies show that corneal sensitivity returns much faster after SMILE, making it a preferred option for patients who already struggle with dry eyes.

Biomechanics and Stability

The cornea is mechanically stronger in its anterior (front) layers. By avoiding a large flap, SMILE leaves these strong anterior layers connected. This results in greater biomechanical stability of the cornea post-surgery compared to LASIK. While this does not completely eliminate the risk of ectasia (bulging of the cornea), it provides a higher safety margin for patients with slightly thinner corneas who might otherwise be borderline candidates for laser surgery.

Limitations: Myopia Only

Currently, the application of SMILE is more limited than LASIK. In the United States, it is FDA-approved primarily for the correction of myopia (nearsightedness) and astigmatism. It is not yet widely approved or used for hyperopia (farsightedness) or for treating presbyopia (aging eyes). Furthermore, because it does not use an excimer laser with wavefront-guided mapping, it generally cannot correct higher-order aberrations (complex visual distortions) as precisely as topography-guided LASIK.

FAQs on SMILE

Does it hurt?

No. The eye is numbed with drops. Patients typically report feeling a sensation of pressure during the laser phase, but no sharp pain. The recovery is quick, with most patients returning to work within 24 to 48 hours.

What if I need an enhancement?

If the first surgery does not fully correct the vision, enhancing a SMILE procedure is trickier than enhancing LASIK. You cannot simply "lift the flap" because there is no flap. Enhancements are usually done by converting the eye to a PRK surface ablation or creating a thin LASIK flap on top of the old SMILE site.

Is the vision instantly clear?

It is slightly slower than LASIK. While LASIK patients often see 20/20 the next morning, SMILE patients may experience a slight "foggy" effect for a few days as the interface where the lenticule was removed settles down.

When to See Your Eye Doctor

If you are interested in laser surgery but have been told in the past that you have "dry eyes" or engage in high-impact activities like martial arts or military service, you should specifically ask a refractive surgeon if you are a candidate for SMILE.

References

https://www.aao.org/eye-health/treatments/smile-laser-eye-surgery

https://pubmed.ncbi.nlm.nih.gov/24664791/

https://www.fda.gov/medical-devices/lasik/what-smile

https://eyewiki.aao.org/Small_Incision_Lenticule_Extraction_(SMILE