LASIK (Laser-Assisted In Situ Keratomileusis) uses a laser to reshape the cornea, correcting common vision problems like nearsightedness, farsightedness, and astigmatism. Regulatory bodies generally set the minimum age for this surgery at 18 years old. However, meeting this age threshold is only the first step in a comprehensive evaluation of candidacy. The decision to proceed with LASIK at age 18 depends on factors including prescription stability, physical eye health, and overall systemic health. These criteria ensure the procedure is safe and provides a lasting visual outcome.
The Critical Factor: Vision Stability
While 18 is the minimum age, the most frequent reason a young adult is deferred is a lack of refractive stability. Eyes continue to grow throughout adolescence, and prescriptions, particularly for nearsightedness (myopia), often change into the early twenties. For a successful and permanent correction, the prescription must have remained stable for at least 12 months, though some surgeons prefer stability up to 24 months.
Stability is defined as having no more than a 0.50 diopter change in prescription power over the required period. Performing the procedure before stability is achieved risks post-operative regression, where the original vision error returns as the eye continues to change. Surgeons examine historical refraction records from previous eye exams to confirm this stability. If a patient’s vision is still progressing, the surgeon will recommend delaying the procedure until the prescription has settled completely.
Prescription limits also play a role in candidacy. Most modern lasers can safely correct high degrees of refractive error, such as up to -12.00 diopters of nearsightedness, but safety depends on the interaction between the prescription and corneal thickness. If a patient has a high prescription, more tissue must be removed, which places a greater demand on the eye’s physical structure. Therefore, even with a stable prescription, a high degree of correction might push the eye beyond safe limits.
Required Physical Eye Health Criteria
Beyond prescription stability, the physical structure of the eye must meet specific parameters to ensure safety and long-term corneal health. The cornea, the clear front surface of the eye, must be thick enough to allow for the creation of the LASIK flap and the subsequent laser ablation. Normal corneal thickness is often around 520 micrometers (µm).
The creation of the flap and the reshaping of the cornea both remove tissue, and a certain amount of untouched tissue must remain to maintain the structural integrity of the eye. The FDA recommends that the remaining layer, called the residual stromal bed, must be at least 250 µm thick after the procedure. Many surgeons prefer a thicker safety margin (275 µm to 300 µm) to minimize the risk of corneal ectasia. Ectasia is a progressive weakening and bulging of the cornea that severely distorts vision.
Other physical factors include the patient’s pupil size and the presence of pre-existing eye conditions. If pupils dilate very large in low light, the laser treatment zone might not fully cover the pupil, potentially leading to visual disturbances like halos or glare at night. Furthermore, conditions such as severe dry eye, uncontrolled glaucoma, or a progressive thinning condition like keratoconus are contraindications for LASIK, as the procedure could worsen the underlying issue.
Systemic Health Considerations
Overall systemic health is a significant factor because it directly impacts the body’s ability to heal and recover from surgery. Conditions that compromise the immune system or affect wound healing increase the risk of complications and often lead to deferral. Active autoimmune disorders, such as lupus or rheumatoid arthritis, are considered contraindications due to the body’s unpredictable inflammatory response.
Uncontrolled diabetes impairs healing and makes the eye susceptible to infection. Hormonal fluctuations can temporarily alter the eye’s prescription and tear film quality. Therefore, women who are pregnant or breastfeeding are advised to wait several months after weaning before undergoing LASIK, as the outcome could be unpredictable. The use of certain systemic medications, such as drugs for severe acne, can also be a temporary or permanent disqualifier due to their effects on the cornea and tear production.
The Pre-Operative Screening Process
Determining eligibility requires a comprehensive, multi-step pre-operative screening process performed by the surgical team. This process is designed to meticulously measure every relevant eye parameter to confirm the patient meets all safety criteria. Patients undergo a thorough eye examination, including measuring visual acuity and performing a dilated refraction to determine the true, relaxed prescription.
Specialized tests are performed to map the cornea’s shape and measure its thickness. Corneal topography uses a non-contact process to create a detailed surface map of the cornea’s curvature, checking for irregularities like keratoconus. Pachymetry measures corneal thickness in micrometers, which is used to calculate the residual stromal bed thickness.
The surgeon uses all this information, including historical prescription records and systemic health history, to create a personalized surgical plan. If the patient is ineligible, the surgeon discusses the reason, such as the need to wait for prescription stability or manage a health condition. Alternatives to LASIK, like Photorefractive Keratectomy (PRK) or Implantable Collamer Lenses (ICLs), may be presented for those disqualified due to thin corneas or high prescriptions.