Vision correction surgery offers freedom from glasses and contact lenses by reshaping the eye’s refractive surface. Modern ophthalmology provides two highly effective laser-based options: Laser-Assisted In Situ Keratomileusis (LASIK) and Small Incision Lenticule Extraction (SMILE). Both procedures correct common vision issues by precisely altering the corneal tissue, but they use fundamentally different mechanical approaches. Choosing between them requires understanding these differences, as they impact the surgical process and the post-operative healing experience.
Understanding the Procedures
Both LASIK and SMILE are refractive surgeries that use advanced laser technology to correct errors like nearsightedness and astigmatism. These conditions occur because the cornea, the transparent front layer of the eye, focuses light improperly onto the retina. Both techniques modify the shape of the corneal stroma (the central layer) to change how light bends, achieving clear vision.
LASIK is the more established procedure, widely used for decades to treat a broad range of refractive errors. It involves two distinct steps and utilizes two different types of lasers. SMILE is a newer, single-step procedure developed as an evolution of laser vision correction, achieving corneal reshaping using a less invasive technique.
Key Procedural Differences
The most significant distinction lies in how the surgeon accesses the corneal stroma for reshaping. In LASIK, a thin, hinged flap is created on the corneal surface using either a microkeratome blade or a femtosecond laser. This flap, measuring approximately 20 millimeters in circumference, is lifted back to expose the underlying tissue.
Once the flap is retracted, an excimer laser precisely removes microscopic amounts of tissue from the stroma, correcting the refractive error. The flap is then repositioned to serve as a natural bandage, adhering without stitches. This two-laser, flap-creation method defines the LASIK procedure.
SMILE is a flapless procedure that uses only a femtosecond laser for the entire correction. The laser creates a small, lens-shaped piece of tissue, known as a lenticule, inside the intact cornea. The lenticule’s shape corresponds to the tissue volume needed to correct the patient’s vision. The surgeon extracts this lenticule through a small, peripheral keyhole incision, typically only 2 to 4 millimeters wide.
Comparing Recovery and Comfort
The difference in incision size and technique leads to varying post-operative experiences, particularly concerning dry eye syndrome. LASIK’s large corneal flap severs a significant number of corneal nerves responsible for regulating tear film production. This nerve disruption commonly results in a higher incidence and severity of temporary post-operative dry eye symptoms.
SMILE’s small keyhole incision disturbs far fewer corneal nerves, causing less impact on the tear reflex arc. Studies suggest SMILE patients experience less severe dry eye symptoms and often have a quicker return to normal tear function in the initial six months. While symptoms resolve in both groups within a year, the initial comfort level is generally greater with SMILE.
Visual recovery also differs slightly. LASIK patients often experience rapid improvement in vision within the first 24 hours due to immediate flap repositioning. SMILE’s visual recovery can be slightly slower initially as the eye heals around the small incision. However, the total time for vision to fully stabilize is similar for both procedures, taking several weeks to months.
The integrity of the cornea, known as corneal biomechanics, is better preserved with the SMILE procedure. The absence of a large flap means more of the anterior corneal stroma, which provides most of the cornea’s structural strength, remains untouched. This preservation may lower the risk of long-term corneal weakening, especially in patients with high degrees of myopia.
Patient Suitability and Treatment Range
The range of refractive errors that can be corrected represents a notable difference in patient suitability. LASIK maintains a broader treatment range and is approved to correct myopia, astigmatism, and hyperopia (farsightedness). This versatility makes LASIK the more widely applicable option for the general population seeking refractive surgery.
SMILE is currently approved primarily for correcting myopia and myopic astigmatism, and it does not treat hyperopia. While SMILE can effectively treat a high degree of nearsightedness, its clinical scope remains more limited than LASIK. Patients with hyperopia will typically find LASIK to be their only laser vision correction option.
The flapless nature of SMILE makes it a preferred option for individuals with certain lifestyle factors. The lack of a flap eliminates the risk of displacement from trauma, making it suitable for athletes or those with professions involving a higher risk of eye injury. For some patients with corneas too thin for a traditional LASIK flap, SMILE’s lenticule extraction method can be a viable alternative.
Ultimately, neither SMILE nor LASIK is universally superior; the determination depends on individual factors. The surgeon weighs the patient’s specific prescription, corneal thickness, existing dry eye concerns, and lifestyle considerations. This ensures selection of the most appropriate and safest method for achieving optimal vision correction.