Myopia, commonly known as nearsightedness, is a widespread vision problem where distant objects appear blurry while near objects remain clear. This condition is a refractive error, meaning the eye does not bend light correctly to achieve a sharp focus. For millions of people who rely on glasses or contact lenses to correct their distance vision, laser eye surgery represents a highly effective and long-term solution. Modern laser vision correction procedures offer a precise method to change the eye’s focusing power and significantly reduce or eliminate the need for corrective eyewear.
Understanding Myopia and the Goal of Laser Correction
Myopia occurs when the shape of the eye is slightly irregular, most often because the eyeball has grown too long from front to back, or the cornea, the clear front surface of the eye, is too steeply curved. In a myopic eye, the light converges at a point in front of the retina, rather than precisely on it, causing distant images to appear out of focus.
The purpose of laser vision correction is to mechanically alter the shape of the cornea to correct this focusing error. By removing microscopic amounts of tissue, the surgeon can flatten the cornea’s curvature. This reshaping ensures that incoming light rays are bent less aggressively and focus directly onto the retina, restoring clear distance vision. The precision of the excimer and femtosecond lasers allows for corrections highly specific to an individual’s refractive error.
The Primary Methods Used to Correct Nearsightedness
Current technology offers three primary methods for laser correction of myopia.
Laser-Assisted In Situ Keratomileusis (LASIK)
LASIK is the most frequently performed procedure due to its rapid visual recovery. The process involves creating a thin, hinged flap on the cornea’s surface, typically using a femtosecond laser. The surgeon lifts this flap, uses an excimer laser to reshape the underlying stromal tissue, and then gently repositions the flap, which adheres without stitches.
Photorefractive Keratectomy (PRK)
PRK is an older but equally effective method, often preferred for patients with thinner corneas or those with professions involving a higher risk of eye trauma. PRK avoids creating a flap; instead, the surgeon removes the cornea’s outermost layer (the epithelium) before using the excimer laser to reshape the surface. The epithelium regenerates over several days, requiring a bandage contact lens during the healing period, which results in a slower visual recovery than LASIK.
Small Incision Lenticule Extraction (SMILE)
SMILE is a newer, minimally invasive technique that uses only a femtosecond laser. The laser creates a precise, lens-shaped piece of tissue, called a lenticule, inside the intact cornea. This lenticule is then extracted through a tiny keyhole incision, reshaping the cornea without a large flap. SMILE is associated with better corneal biomechanical stability and less short-term dry eye compared to LASIK.
Who Qualifies for Laser Vision Correction
Not everyone with myopia is a suitable candidate for laser vision correction, and a thorough preoperative examination is necessary to ensure safety and optimal results. A fundamental requirement is that the patient must be at least 18 years old, as the eyes must be fully developed and the refractive error must be stable. The prescription should not have changed significantly for at least 12 months prior to the procedure.
Adequate corneal thickness is another limiting factor, particularly for LASIK and high prescriptions. A certain amount of tissue must remain after the laser ablation to maintain the cornea’s structural integrity. Patients with prescriptions that are too high may be better suited for alternative procedures like implantable lenses.
Certain pre-existing health and eye conditions can disqualify a patient, as they can interfere with the healing process or be exacerbated by the surgery. These include uncontrolled conditions like severe dry eye syndrome, active eye infections, uncontrolled glaucoma, or corneal diseases like keratoconus. Pregnant or nursing women are also temporarily ineligible due to hormonal fluctuations that can affect vision stability and healing.
Long-Term Expectations and Stability of Results
The physical change to the cornea made by the laser is permanent; the tissue that has been removed or reshaped will not grow back. This means the initial correction of the myopic error is stable for the long term in most patients. The majority of individuals maintain excellent, stable vision for many years following the procedure.
However, the eye can still undergo natural changes over a lifetime that may affect vision. A phenomenon known as regression can occur, where a small amount of the myopic error gradually returns over time, often years after the initial procedure. Regression is generally mild, but it is more common in patients who had a high degree of myopia corrected.
Laser surgery does not prevent age-related vision changes, such as presbyopia (the need for reading glasses that typically develops after age 40) or the eventual formation of cataracts. While LASIK offers a fast recovery, common temporary side effects across all procedures include dry eyes and visual disturbances like halos or glare. These usually improve significantly within the first few months.