LASIK, or Laser-Assisted In Situ Keratomileusis, is a widely recognized laser eye surgery that has transformed vision correction for many individuals. This outpatient procedure utilizes lasers to address refractive errors, which occur when the eye cannot properly bend light to focus it onto the retina, leading to blurred vision. LASIK reshapes the cornea, the clear, dome-shaped front surface of the eye, to improve how light focuses on the retina. This surgical method corrects nearsightedness (myopia), farsightedness (hyperopia), and astigmatism by altering the corneal curvature.
How LASIK Corrects Nearsightedness
Nearsightedness, also known as myopia, occurs when distant objects appear blurry while close-up vision remains clear. This condition typically arises because the eyeball is too long or the cornea is too steeply curved, causing light to focus in front of the retina. The eye’s natural lens and cornea work together to refract light, but in myopia, this refractive power is excessive for the eye’s length. As a result, the image on the retina is out of focus, leading to blurry distance vision.
LASIK addresses nearsightedness by precisely reshaping the cornea to reduce its curvature. During the procedure, a surgeon first creates a thin, hinged flap on the corneal surface using a femtosecond laser or microkeratome. This flap is lifted to expose the underlying stromal tissue. An excimer laser removes tissue from the central part of the exposed stroma.
This targeted tissue removal effectively flattens the central cornea. By flattening the cornea, the eye’s refractive power is reduced, allowing light to focus correctly on the retina. After laser ablation, the corneal flap is repositioned, adhering naturally without stitches. This flattening helps light focus directly on the retina, improving clear distance vision for individuals with myopia.
How LASIK Corrects Farsightedness
Farsightedness, or hyperopia, makes close objects appear blurry, though distant vision might be clear. This occurs because the eyeball is typically shorter than average, or the cornea has insufficient curvature, causing light to focus behind the retina. The eye’s focusing power is not strong enough to converge light accurately on the retina, especially for near tasks. Consequently, the brain receives a blurred image, especially when focusing on objects up close.
For farsightedness, LASIK aims to increase the cornea’s focusing power by making it steeper. A thin corneal flap is created and lifted, similar to nearsightedness correction, to access the underlying stromal tissue. However, instead of flattening the central cornea, the excimer laser removes tissue from the periphery. This peripheral tissue removal causes the central cornea to steepen, effectively increasing its curvature.
Steepening the central cornea enhances the eye’s refractive power, allowing light to focus directly onto the retina. This corrects the blurred vision associated with hyperopia. The corneal flap is then meticulously returned to its original position, reattaching without sutures. This reshaping enables clearer vision for both near and distant objects.
Key Considerations for LASIK Eligibility
Suitability for LASIK involves a comprehensive evaluation of factors beyond the type of refractive error. Candidates are typically 18 years or older, as vision should have stabilized. A stable prescription is important, meaning vision has not changed significantly for at least one year prior to surgery. This stability indicates that the eye’s refractive error has matured and is less likely to regress post-procedure.
Corneal thickness is another factor, as the procedure removes corneal tissue. Sufficient thickness ensures the eye’s structural integrity after reshaping. General eye health is assessed to rule out conditions like severe dry eye, advanced glaucoma, cataracts, or keratoconus (where the cornea thins and bulges into a cone shape). Certain systemic health conditions, like uncontrolled diabetes, can impact healing and may disqualify a candidate. A thorough eye examination by a qualified professional determines if an individual is an appropriate candidate for LASIK and discusses realistic expectations for visual outcomes.