LASIK (Laser-Assisted In Situ Keratomileusis) is a widely recognized surgical procedure designed to correct refractive errors, aiming to reduce or eliminate the need for glasses or contact lenses. It reshapes the cornea, the clear front surface of the eye, to improve how light focuses onto the retina. While LASIK offers significant vision improvement for many, its suitability is not universal, particularly for individuals with very high prescription levels.
General LASIK Candidacy
Beyond prescription strength, several factors determine LASIK candidacy. Patients must be 18 or older, as vision stabilizes by this age. A stable prescription, with no significant changes for at least one to two years, is required for lasting results.
Overall eye health is important. Individuals should not have active eye diseases like glaucoma, cataracts, severe dry eye, or corneal thinning disorders such as keratoconus. Certain systemic conditions, including autoimmune diseases or uncontrolled diabetes, and some medications can interfere with healing, making LASIK unsuitable. Adequate corneal thickness is also a factor, as the procedure involves reshaping the cornea.
Specific Prescription Thresholds
LASIK addresses various refractive errors, each with its own upper limits. For nearsightedness (myopia), LASIK corrects prescriptions up to -12.00 diopters (D). Farsightedness (hyperopia) has an upper limit of +4.00 to +6.00 D. Astigmatism, an irregular corneal curvature, is corrected up to 6.00 D, usually with myopia or hyperopia.
These figures are guidelines. Advanced laser technologies like wavefront-guided LASIK can expand the treatable range, allowing for more precise mapping and correction of the eye’s unique imperfections. Eligibility depends on individual corneal thickness and the surgeon’s comprehensive evaluation.
Why Prescription Limits Exist
Prescription limits for LASIK are based on the procedure’s underlying mechanics and the need to maintain eye health. LASIK reshapes the cornea by removing microscopic tissue with a laser. Higher prescriptions necessitate more corneal tissue removal.
Maintaining sufficient remaining corneal tissue, known as the residual stromal bed, is important. The U.S. Food and Drug Administration (FDA) recommends leaving at least 250 micrometers (µm) of untouched corneal tissue to preserve integrity and prevent complications like ectasia, where the cornea bulges outward, leading to distorted vision. Many surgeons prefer to leave 275-300 µm for added safety. Removing too much tissue can decrease visual outcome predictability and increase the risk of enhancement surgeries or less-than-optimal vision quality.
Other Vision Correction Options
For individuals with prescriptions too high for LASIK or who are otherwise unsuitable candidates, several other vision correction options are available. Photorefractive Keratectomy (PRK) is a surface-based laser procedure where the outer corneal layer is removed before reshaping, without creating a flap. This can be an option for some patients with thinner corneas or higher prescriptions, though it involves a longer recovery period than LASIK.
Implantable Collamer Lenses (ICL), or phakic intraocular lenses, are another solution for very high myopia or hyperopia. This procedure involves surgically implanting a thin, biocompatible lens inside the eye, in front of the natural lens, without removing it. ICLs can correct a broad range of nearsightedness (-3.0 D to -20.0 D) and astigmatism (1.0 D to 4.0 D).
Refractive Lens Exchange (RLE) involves replacing the eye’s natural lens with an artificial intraocular lens. Similar to cataract surgery, RLE corrects refractive errors rather than removing a cloudy lens. It is often considered for older patients or those with very high prescriptions, as it can correct almost any level of myopia or hyperopia. Glasses and contact lenses remain safe and effective vision correction methods.