Laser eye surgery, including procedures like LASIK and PRK, has become a widely accepted method for correcting common vision issues such as nearsightedness, farsightedness, and astigmatism. This procedure works by precisely reshaping the cornea to adjust how light is focused onto the retina. While millions have successfully achieved clear vision without glasses or contact lenses, this surgery is not universally suitable for every individual. A thorough screening process is mandatory to evaluate the physical structure of the eye and the patient’s overall health to ensure safety and long-term effectiveness.
Necessary Eye Health Requirements
The structural integrity and health of the cornea are the most frequent reasons a patient may be ineligible for laser eye surgery. Reshaping the cornea requires a sufficient amount of tissue. Patients with naturally thin corneas may not have enough material to safely allow for the tissue removal needed to correct their prescription. Removing too much tissue compromises the physical strength of the eye, potentially leading to a complication known as corneal ectasia, where the cornea bulges outward and distorts vision.
Corneal shape abnormalities are a major contraindication, particularly for individuals with keratoconus, a progressive condition where the cornea thins and assumes a cone-like shape. Even a subtle version of keratoconus can be destabilized by the surgery, making a detailed topographical map of the cornea necessary for all candidates. Active eye infections, such as herpes simplex keratitis, or uncontrolled eye diseases like advanced glaucoma or significant cataracts, must be resolved or treated before surgery.
Severe or uncontrolled dry eye syndrome is a common disqualifier because the procedure can temporarily worsen tear film stability, leading to prolonged discomfort and impaired healing. Surgeons must assess tear production and quality, often requiring patients with pre-existing dry eye to undergo treatment before being considered for the procedure. If an underlying condition requires a different surgical approach, such as a cataract causing significant vision impairment, laser vision correction is deferred in favor of cataract surgery.
Systemic Health Conditions Affecting Healing
A patient’s systemic health plays a significant part in the healing and recovery process following laser eye surgery. Conditions that impair the body’s ability to heal connective tissue increase the risk of complications and poor visual outcomes. Uncontrolled autoimmune diseases, such as Lupus or Rheumatoid Arthritis, interfere with the predictable healing of the corneal tissue.
Conditions that compromise microvascular health, notably poorly controlled diabetes, may make a patient unsuitable because high blood sugar levels slow recovery and increase infection risk. Patients taking immunosuppressive medications or oral corticosteroids may also experience delayed healing. A history of keloid formation (excessive scar tissue growth on the skin) is a concern for surface procedures like PRK due to the potential for excessive corneal haze formation.
Temporary systemic changes also render many patients temporarily ineligible, including those who are pregnant or breastfeeding. Hormonal fluctuations during these periods cause temporary changes in corneal curvature and refractive error, making pre-operative measurements unreliable for a permanent correction. Surgeons advise waiting for several months after hormone levels have stabilized to ensure the refractive error returns to a stable baseline before proceeding.
Limitations Based on Vision Prescription and Age
Eligibility for laser eye surgery is subject to criteria related to the patient’s vision prescription and age. The procedure is typically only performed on adults, with a minimum age requirement generally set at 18 to 21 years old. This requirement exists because the eye continues to grow and the vision prescription can change significantly throughout adolescence.
A stable prescription is a fundamental requirement, meaning the refractive error should not have changed beyond a small threshold for at least one to two years before the procedure. If the prescription is still actively changing, the surgery’s results will be short-lived as the underlying error continues to progress. There are also limits to the range of vision correction that can be safely achieved with a laser.
Excessively high prescriptions, such as severe myopia beyond -10.00 diopters or hyperopia above +4.00 diopters, may exceed the safe treatment range. These prescriptions require the removal of too much corneal tissue, increasing the risk of corneal instability or a poor outcome. In these cases, alternative procedures like an implantable collamer lens (ICL) may be recommended. Older adults may be better suited for lens-based procedures if they show signs of early cataract formation that laser eye surgery cannot address.