LASIK, or Laser-Assisted in Situ Keratomileusis, is a popular refractive surgery that reshapes the cornea to correct common vision problems like nearsightedness, farsightedness, and astigmatism. While millions have benefited, it is not universally suitable for everyone. A comprehensive screening process is necessary before surgery to ensure patient safety and maximize a successful outcome. Ineligibility often stems from concerns that the procedure may compromise the eye’s structural integrity or interfere with natural healing mechanisms.
Required Corneal Thickness and Vision Stability
LASIK necessitates a healthy, appropriately thick cornea for a safe procedure. It involves creating a thin flap on the cornea’s surface and using a laser to remove tissue from the underlying layer, called the stroma, to correct the refractive error. If the cornea is too thin, removing tissue compromises structural integrity, increasing the risk of corneal ectasia, where the cornea weakens and bulges forward. Surgeons often prefer a minimum preoperative thickness greater than 500 micrometers, but the more stringent safety measure is the residual stromal bed thickness, targeted to be at least 300 micrometers.
Beyond physical structure, a stable vision prescription is a prerequisite for long-lasting results. The prescription must not have changed significantly for at least 12 months, and often 18 to 24 months, before the procedure. Performing LASIK on a changing prescription means the correction will likely lose effectiveness as the eye continues to evolve. This stability requirement is why patients must be at least 18 years old, as the eyes of younger individuals are often still developing.
Refractive errors that are too high, such as extreme nearsightedness, may fall outside the treatable range for LASIK. Correcting a high prescription requires removing significant corneal tissue, which would leave the remaining cornea too thin and structurally unstable. For these cases, alternative procedures are often considered safer and more effective.
Disqualifying Ocular Conditions
Chronic or active conditions affecting the eye can interfere with healing or compromise the long-term result. Severe dry eye syndrome is a common reason for disqualification, as the procedure can temporarily worsen dryness and discomfort, potentially leading to delayed healing or suboptimal visual outcomes. Patients with existing dry eye must undergo treatment to manage the condition before being reconsidered for LASIK.
Conditions that compromise the cornea’s shape or health are absolute contraindications. Keratoconus, a progressive disorder where the cornea thins and bulges into a cone shape, makes LASIK unsafe because the laser treatment would further weaken the unstable structure. Active eye infections, such as conjunctivitis, or any inflammation must be resolved prior to surgery to prevent serious post-operative complications.
Uncontrolled glaucoma, characterized by increased intraocular pressure, is a concern. Pressure changes during the LASIK procedure could worsen the condition in patients with advanced or poorly managed glaucoma. Similarly, if a patient has a visually impairing cataract, LASIK is inappropriate since it only reshapes the cornea and does not address the cloudiness of the natural lens.
Systemic Health Issues and Temporary Limitations
Health issues affecting the body’s healing capacity or immune system can disqualify a candidate. Systemic autoimmune diseases, such as Lupus, Rheumatoid Arthritis, or Sjögren’s Syndrome, are traditionally contraindications because the immune system may interfere with eye recovery, potentially leading to poor wound healing or corneal melting. However, some surgeons may perform LASIK if the autoimmune condition is well-controlled and inactive, though this requires careful individual assessment.
Uncontrolled diabetes presents a risk because it compromises the body’s ability to heal and may lead to vision fluctuations, making precise refractive correction difficult. While well-controlled diabetes is often a relative contraindication, poorly managed blood sugar levels are an absolute contraindication due to the higher risk of complications and infection.
Temporary physiological states necessitate postponement of the procedure. Pregnancy and nursing are contraindications because hormonal fluctuations can cause temporary changes in corneal shape and vision stability. Surgeons advise waiting until vision has stabilized, typically several months after childbirth or cessation of breastfeeding, before considering LASIK.
Alternatives for Those Who Are Ineligible
Individuals who do not qualify for LASIK still have several advanced surgical options to achieve visual freedom. Photorefractive Keratectomy (PRK) is often recommended for candidates with corneas too thin for LASIK or those with specific occupational needs that preclude a corneal flap. PRK involves reshaping the cornea’s surface without creating a flap, which preserves more underlying tissue, though it involves a longer and more uncomfortable recovery period than LASIK.
Another alternative is Phakic Intraocular Lenses (ICLs), which are permanent, corrective lenses surgically implanted inside the eye without removing the natural lens. ICLs are an excellent option for patients with very high prescriptions outside the range treatable by laser, or for those with thin corneas who want to avoid corneal tissue removal. Unlike laser procedures that permanently alter the cornea, ICL implantation is reversible, offering a unique benefit.