LASIK surgery offers a pathway to reduced dependence on corrective lenses, but it is not a universally suitable procedure. Determining eligibility involves a comprehensive pre-operative evaluation to confirm that the eye can safely undergo and recover from the laser treatment. A successful outcome relies on both the physical condition of the eye and the patient’s overall health status. The screening process identifies specific contraindications—factors that increase the risk of complications or lead to unpredictable results. These limitations ensure patient safety and maximize the potential for long-term visual success.
Structural Factors and Existing Eye Disease
The physical condition of the cornea, the clear front surface of the eye, is a primary determinant of suitability for LASIK. The procedure works by reshaping this tissue, meaning it must have sufficient thickness and a regular shape. If the cornea is measured to be too thin, tissue removal could compromise the structural integrity of the eye, significantly raising the risk of a complication called corneal ectasia, where the cornea bulges outward.
Corneal topography, which maps the surface curvature of the eye, is used to screen for conditions like keratoconus. This progressive disease causes the cornea to thin and become cone-shaped. Performing LASIK on an eye with keratoconus, even in its mildest form, can accelerate the condition and cause severe vision loss. Other pre-existing eye conditions can also disqualify a candidate, including severe chronic dry eye syndrome, which LASIK can temporarily worsen and make chronic.
Existing diseases like severe glaucoma, which involves elevated intraocular pressure, or certain retinal diseases may also rule out the procedure. LASIK can temporarily increase eye pressure during the surgery, and the procedure may interfere with the long-term management of advanced glaucoma. Patients with uncontrolled active eye infections, such as those caused by herpes simplex virus, must have their condition resolved and stable before any consideration of laser vision correction.
Unstable Vision and Prescription Extremes
A stable vision prescription is a fundamental requirement for a successful LASIK outcome, as the laser correction is intended to be permanent. Most surgeons require that a patient’s prescription has not changed for at least one to two consecutive years before the procedure. This stability is particularly relevant for younger individuals; while the United States Food and Drug Administration (FDA) approves LASIK for those 18 and older, many practitioners prefer to wait until the early to mid-twenties to ensure the eye has completed its natural development.
The technical limits of the excimer laser also place constraints on candidacy based on the magnitude of the refractive error. Prescriptions exceeding certain thresholds require a large amount of tissue removal, which can weaken the cornea and increase the risk of poor visual quality. For nearsightedness (myopia), the correction limit is generally around -10.00 to -12.00 diopters, while for farsightedness (hyperopia), the limit is typically +4.00 to +6.00 diopters. Correcting astigmatism is also limited, often falling around 6 diopters, with higher corrections more likely to result in regression or irregular healing.
Systemic Health and Healing Concerns
The body’s ability to heal following surgery is significantly influenced by overall health, making certain systemic conditions problematic for LASIK recovery. Autoimmune disorders, such as lupus, rheumatoid arthritis, and Sjögren’s syndrome, are generally considered relative contraindications. They compromise the immune system and impair wound healing. The risk of severe post-operative complications, including corneal melting or non-healing ulcers, is elevated in patients with these conditions due to chronic inflammation and poor tissue repair.
Uncontrolled diabetes can also be a complicating factor, as fluctuating blood sugar levels can lead to unstable vision and impaired healing, making the eye more vulnerable to infection. Hormonal changes, such as those experienced during pregnancy and breastfeeding, temporarily alter the corneal shape and affect vision stability. Surgeons typically recommend waiting several months after these periods to allow vision to stabilize before considering the procedure.
Certain medications can also interfere with the healing process or exacerbate post-operative symptoms, including immunosuppressive drugs and some acne treatments like isotretinoin. Isotretinoin is known to cause severe dryness, which is a significant concern since LASIK itself can induce temporary dry eye. The presence of any health condition or medication that affects the body’s inflammatory or healing response warrants a careful, case-by-case evaluation before proceeding with laser vision correction.