LASIK (Laser-Assisted In Situ Keratomileusis) reshapes the cornea to correct common refractive errors, reducing or eliminating the need for glasses or contact lenses. As an elective surgical procedure, it requires strict screening protocols to ensure safety and effectiveness. The primary goal of this evaluation is to identify pre-existing conditions that could compromise the eye’s structural integrity, interfere with healing, or lead to an unpredictable surgical outcome.
Unsuitable Cornea Structure or Ocular Conditions
The cornea, the transparent front surface of the eye, is the primary target of laser correction, and its physical state is the most common reason for disqualification. Sufficient corneal thickness is required because LASIK involves creating a thin flap and then ablating underlying tissue to change the curvature. If the cornea is too thin, the remaining tissue (the residual stromal bed) may be left too weak, risking ectasia, a severe complication where the cornea bulges outward and distorts vision.
Keratoconus, a pre-existing condition where the cornea naturally thins and bulges into a cone shape, is an absolute disqualifier because LASIK would further destabilize the already compromised tissue. Ocular diseases involving the clouding of the lens, such as severe cataracts, or conditions affecting internal eye pressure, like uncontrolled glaucoma, also preclude LASIK. Furthermore, severe or chronic dry eye syndrome is a concern, as LASIK temporarily reduces tear production during healing, leading to prolonged discomfort and poor visual results.
Vision Stability and Refractive Error Limits
Successful LASIK depends on correcting a stable prescription, meaning the refractive error has not changed significantly for a period of at least one to two years before the procedure. Unstable vision, often seen in adolescents or young adults, means the eye is still changing, and surgical results would quickly become inaccurate. Therefore, candidates must typically be at least 18 years old, though many surgeons prefer waiting until the early 20s to ensure maximum stability.
There are physical limits to the amount of correction an eye can safely receive, measured in diopters (D). LASIK is generally approved to correct up to -12.00 D of myopia and up to +6.00 D of hyperopia. Astigmatism correction is typically limited to about 6.00 D. Attempting to treat extremely high refractive errors requires removing too much corneal tissue, increasing the risk of structural instability and leading to less predictable outcomes.
Systemic Diseases and Healing Impairments
The body’s overall health plays a significant role in the eye’s ability to heal properly following the procedure. Systemic diseases that compromise the immune system or affect wound healing are major contraindications for LASIK. Autoimmune conditions, such as lupus or rheumatoid arthritis, can impair the body’s inflammatory response and lead to unpredictable or poor corneal healing.
Similarly, uncontrolled diabetes is a concern because high blood sugar levels can impede the body’s natural repair mechanisms and increase the risk of post-operative infection. Certain medications, including high-dose or prolonged oral steroids and some immunosuppressants, can also interfere with the corneal healing process, making LASIK inadvisable. These systemic factors affect the entire body’s ability to repair the surgical wound in the cornea.
Temporary Conditions and Lifestyle Considerations
Some disqualifications are temporary and require a waiting period until the condition resolves. Pregnancy and breastfeeding cause hormonal fluctuations that temporarily alter vision and tear production, making it difficult to obtain an accurate prescription. Furthermore, medications used during and after the procedure are generally not recommended for pregnant or nursing individuals.
Individuals who wear soft contact lenses must stop using them for a specified “washout” period, typically one to four weeks, before pre-operative measurements. Discontinuing use allows the cornea to return to its natural shape, ensuring the most accurate treatment planning. Certain occupations, particularly in the military or law enforcement, may require a different type of laser procedure, such as Photorefractive Keratectomy (PRK), which is sometimes preferred for high-impact roles.