LASIK (Laser-Assisted in Situ Keratomileusis) is a popular elective procedure designed to correct common refractive errors, often reducing or eliminating the need for glasses or contact lenses. Since this surgical procedure permanently alters the cornea, a thorough screening process is undertaken to evaluate candidacy. This assessment maximizes the chances of a successful outcome and ensures the long-term safety and stability of the eye. Factors ranging from the physical structure of the eye to a person’s general health can lead to disqualification.
Physical and Structural Limitations of the Eye
The cornea, the clear, dome-shaped front surface of the eye, is the structure LASIK reshapes, making its physical characteristics paramount for safety. The most significant structural limitation is the original thickness of the cornea. LASIK involves creating a thin flap and then removing tissue from the underlying corneal bed (stroma) to correct the prescription.
A primary concern is ensuring an adequate residual stromal bed (RSB) thickness remains after laser ablation. Surgeons adhere to a minimum RSB of 250 micrometers to maintain the cornea’s biomechanical integrity. This minimum thickness prevents post-LASIK ectasia, a progressive thinning and bulging of the cornea that causes severe vision distortion. Total corneal thickness must be sufficient to accommodate the flap and the tissue removal required for the specific refractive error.
A high degree of myopia (nearsightedness) requires a greater amount of corneal tissue removal, directly reducing the RSB. For patients with thinner corneas, a high prescription may push the required ablation depth beyond safe limits. Furthermore, patients with naturally large pupils may not be ideal candidates. The treatment zone must be larger than the pupil to prevent halos and glare at night. If the treatment zone is smaller than the dilated pupil, the transition area can scatter light, leading to visual disturbances in low-light conditions.
Pre-existing Ocular Health Concerns
Certain pre-existing eye diseases are definitive contraindications for LASIK, as surgery could worsen the condition or lead to unpredictable healing. Keratoconus is a serious disqualifier; this progressive disorder causes the cornea to thin and bulge into an irregular cone shape. Since LASIK weakens the cornea by removing tissue, performing the procedure with keratoconus can accelerate the disease’s progression, resulting in irreversible visual deterioration.
Chronic, severe dry eye syndrome is a common reason for disqualification because creating the corneal flap temporarily disrupts the nerves that stimulate tear production. While most patients experience some dryness post-surgery, those with pre-existing severe symptoms risk long-term discomfort, impaired healing, and poor visual quality. Any active eye infection or inflammation must be fully resolved before surgery to minimize complications.
Uncontrolled or advanced glaucoma is a concern because LASIK can compromise disease management. The procedure can temporarily elevate intraocular pressure, which is harmful to the optic nerve in glaucoma patients. Furthermore, the permanent change to the cornea’s shape and thickness can lead to inaccurate pressure readings after surgery, making long-term monitoring more challenging.
Systemic Conditions Affecting Healing
A person’s general systemic health plays a direct role in the body’s ability to heal following surgery, including LASIK. Conditions that compromise the immune system or affect wound healing increase the risk of complications. Active autoimmune disorders, such as Lupus, Rheumatoid Arthritis, or Sjögren’s syndrome, have historically been considered absolute contraindications.
These conditions can impair the body’s normal inflammatory and healing responses, potentially leading to poor flap adherence, delayed healing, or corneal melt. The approach has become more nuanced, however. Some surgeons now consider patients with well-controlled autoimmune diseases and no related eye manifestations as potential candidates. Primary Sjögren’s syndrome, which severely affects tear production, remains a strong contraindication due to the high risk of severe postoperative dry eye.
Uncontrolled diabetes poses a substantial risk because high blood sugar impairs corneal healing and increases susceptibility to infection. While well-controlled diabetes is often considered a relative contraindication, poorly managed blood sugar levels are an absolute systemic disqualifier. Certain medications, such as immunosuppressants or drugs for severe acne, can interfere with corneal healing and may require a waiting period before LASIK.
Temporary Restrictions and Vision Stability
Some disqualifying factors are not permanent and simply require a waiting period until conditions resolve or stabilize. The most fundamental temporary restriction is age; most refractive surgeons require patients to be at least 18 years old. The primary reason for this age minimum is the need to ensure the refractive error (prescription) is stable over time.
A stable prescription, defined as no significant change for at least 12 months, is necessary to ensure the LASIK correction is accurate and long-lasting. Vision that continues to change suggests the eye is still developing or undergoing a myopic shift. Performing surgery prematurely would likely result in the need for a re-treatment later, so this waiting period ensures the treatment is based on a mature and fixed refractive error.
Hormonal fluctuations can cause temporary changes in vision, making pregnancy and nursing periods temporary contraindications. Hormones can cause fluid retention, which alters the shape and curvature of the cornea, leading to a temporary shift in refractive error. Patients are advised to wait until after they have finished breastfeeding and their hormones have returned to normal (which can take several months) to ensure the procedure is based on the true, stable prescription.