Refractive surgery corrects common vision issues like nearsightedness and astigmatism, often eliminating the need for glasses or contact lenses. The most popular advanced procedures are Laser-Assisted In Situ Keratomileusis (LASIK) and Small Incision Lenticule Extraction (SMILE). Patients considering vision correction often focus on the safety and long-term risk profile of each technique. Evaluating their comparative safety requires understanding the fundamental differences in how these two laser surgeries interact with the eye’s anatomy.
How SMILE and LASIK Procedures Differ
The core difference between LASIK and SMILE lies in their mechanical approach to reshaping the cornea. LASIK is a two-step process requiring the creation of a thin, hinged flap on the corneal surface. This flap is typically created using a femtosecond laser or a microkeratome blade. The surgeon lifts the flap to expose the underlying tissue, which is reshaped using a second laser, an excimer laser, before the flap is repositioned as a natural bandage.
SMILE is a minimally invasive, flapless procedure that uses only a femtosecond laser. The laser creates a precise, lens-shaped piece of tissue, known as a lenticule, within the middle layer of the cornea. This lenticule corresponds to the patient’s prescription and is the tissue removed to correct the refractive error. The surgeon extracts the lenticule through a small, peripheral incision, typically two to four millimeters in length.
This distinction means LASIK involves a large circular cut, while SMILE uses a significantly smaller incision. The LASIK method requires two separate lasers, whereas SMILE uses a single femtosecond laser for the entire procedure. Avoiding the creation of a large flap fundamentally changes how the eye’s structure is altered during SMILE surgery.
Comparative Risk Profiles and Complications
The difference in surgical technique leads to distinct risk profiles concerning corneal structural integrity. LASIK complications are often related to the corneal flap, which is a potential point of weakness. Flap-related issues include dislocation or displacement, which can occur from trauma or rubbing the eye years after the procedure. Other risks include epithelial ingrowth and the formation of striae (folds in the flap), which can affect vision quality.
Since SMILE is flapless, it eliminates the possibility of flap-related complications. This is a safety advantage, especially for patients with active lifestyles or those involved in contact sports. The small incision in SMILE leaves the anterior portion of the corneal tissue largely intact. Preservation of this anterior stromal tissue reduces biomechanical stress on the eye’s structure.
SMILE has its own rare procedural risks. The surgeon must manually separate and remove the lenticule, which can present technical difficulty. If suction is lost during the laser portion, the procedure may need to be aborted. However, the greater preservation of corneal tissue in SMILE may lower the theoretical risk of developing ectasia, a progressive thinning and bulging of the cornea.
Recovery Timeline and Post-Procedure Comfort
The immediate post-operative experience differs, particularly concerning the speed of visual improvement. LASIK provides rapid initial recovery, with many patients achieving 20/20 vision or better by the first day after surgery. The flap acts as a protective layer, allowing for quick visual stabilization. With SMILE, the initial recovery of sharp vision is slightly slower, often taking a few days to a week to fully clear, though patients return to regular activities quickly.
A major factor influencing post-procedure comfort is the impact on corneal nerves. The large flap created during LASIK severs a significant number of corneal nerves responsible for tear production and surface sensation. This nerve disruption is the primary reason for the high incidence of temporary Post-Operative Dry Eye Syndrome following LASIK. Symptoms typically resolve as the nerves regenerate over six to twelve months.
SMILE’s small incision technique significantly reduces the transection of these corneal nerves, preserving more nerve integrity. This preservation correlates with a lower incidence and reduced severity of post-operative dry eye symptoms compared to LASIK. SMILE patients tend to experience less dryness and a faster return to normal tear function. This makes SMILE a preferable option for patients who have pre-existing dry eye tendencies.
Final Visual Acuity and Treatment Limitations
Both LASIK and SMILE are highly effective and predictable procedures, achieving excellent final visual outcomes for correcting nearsightedness (myopia) and astigmatism. Research indicates that the proportion of eyes achieving an uncorrected distance visual acuity of 20/20 or better is comparable between the two methods over the long term. This suggests that in terms of ultimate visual sharpness, both procedures are similarly efficacious for suitable candidates.
The primary difference relates to the range of refractive errors each procedure can treat. LASIK remains the more versatile option, capable of correcting myopia, astigmatism, and hyperopia (farsightedness). This broader treatment range makes LASIK an option for a wider spectrum of patients needing vision correction.
SMILE is currently approved and most effective for treating myopia and certain levels of myopic astigmatism. It is not utilized to treat hyperopia, which limits its applicability for farsighted patients. While both procedures offer similar results for specific prescriptions, the choice may be determined by whether the patient’s refractive error falls within the treatment parameters of the SMILE procedure.