LASIK (Laser-Assisted In Situ Keratomileusis) is a widely performed refractive surgery that corrects vision problems by reshaping the cornea. The procedure aims to reduce or eliminate the need for glasses or contact lenses for individuals with myopia, hyperopia, or astigmatism. Determining qualification for this elective surgery is highly individualized and relies on meeting a strict set of medical and ocular criteria. A thorough assessment must confirm a candidate’s suitability to ensure the procedure’s safety and effectiveness.
Foundational Eligibility Requirements
A basic requirement for all candidates is a minimum age of 18, though many surgeons prefer patients to be in their early twenties. The eye must have reached ocular maturity, ensuring the results of the permanent reshaping procedure are predictable. Stability of the refractive error is a prerequisite, typically defined as no significant change in the eye prescription for at least one year prior to the evaluation. This ensures the laser correction addresses a static vision problem.
Candidates must also be in good overall health, free from acute infections or systemic illnesses that could compromise the body’s ability to heal post-surgery.
Essential Ocular Criteria
The physical characteristics of the eye, particularly the cornea, are meticulously measured to confirm candidacy. Cornea thickness is a primary factor, as LASIK involves creating a thin flap and using an excimer laser to ablate underlying tissue to correct the refractive error. Adequate corneal tissue must remain after the procedure to maintain structural integrity. The extent of the refractive error must fall within the treatable range of the laser technology.
Refractive Limits
For nearsightedness (myopia), correction is generally approved up to -12 diopters, and farsightedness (hyperopia) is typically limited to around +6 diopters. Astigmatism, an irregular curvature of the cornea, can often be corrected up to 6 diopters. Prescriptions exceeding these limits may require excessive tissue removal, which could lead to complications or an unsatisfactory result.
Pupil Size
Pupil size is another important measurement, especially in low-light conditions. If pupils dilate too widely in the dark, the uncorrected outer edge of the cornea may be exposed. This increases the risk of night vision side effects like glare, halos, or starbursts. Surgeons measure the pupil’s maximum diameter to assess this risk. While large pupils do not always disqualify a person, they require careful consideration in the treatment plan.
Medical Conditions That Disqualify
Certain health issues, both ocular and systemic, can prevent a person from safely undergoing LASIK.
Systemic Conditions
Autoimmune disorders like lupus or rheumatoid arthritis are often absolute contraindications because they impair the body’s natural healing process, increasing the risk of poor recovery and complications. Uncontrolled diabetes can also hinder healing and introduce risks due to potential blood vessel abnormalities in the eye.
Ocular Conditions
Specific eye diseases also disqualify candidates, as the procedure could worsen the underlying condition. Keratoconus, a progressive thinning that causes the cornea to become cone-shaped, is a disqualifier because LASIK can further compromise the cornea’s shape and strength. Conditions such as severe or progressive dry eye syndrome, advanced glaucoma, or active eye infections like conjunctivitis must be resolved or treated before surgery can be considered.
Temporary Disqualifiers
Pregnancy and nursing are temporary disqualifiers. Hormonal fluctuations during these periods cause temporary changes in vision and tear production, making it difficult to determine a stable prescription for the procedure. Surgeons recommend waiting several months after nursing has concluded and hormones have stabilized before proceeding with a LASIK consultation.
The Pre-Surgical Screening Process
The final determination of candidacy occurs through a comprehensive pre-surgical screening process. This evaluation involves a detailed eye exam and a series of advanced diagnostic tests to gather the necessary data for surgical planning.
Contact Lens Requirements
Patients who wear soft contact lenses must discontinue use for at least seven days, while those with hard or rigid gas-permeable lenses may need to stop for a month or more. Discontinuing wear is necessary because contact lenses temporarily alter the cornea’s shape, ensuring measurements are taken on the cornea’s natural contour.
Diagnostic Testing
Specialized equipment maps the eye’s structure with high precision. Corneal topography creates a detailed map of the corneal surface curvature, while pachymetry accurately measures corneal thickness. Wavefront analysis may also be used to detect subtle vision imperfections beyond the standard prescription, allowing for a highly customized treatment. The surgeon uses this information to confirm eligibility and discuss expected outcomes or propose alternative procedures like PRK if LASIK is not suitable.