Laser eye surgery, including procedures like LASIK and Photorefractive Keratectomy (PRK), corrects vision problems by using a focused beam of light to reshape the cornea. This improves how light is focused onto the retina, reducing dependence on glasses or contact lenses. Not everyone is a suitable candidate, so eligibility requires a thorough assessment of general health, eye structure, and visual stability. A detailed consultation determines if the procedure can be performed safely and achieve the desired visual outcome.
Basic Prerequisites for Surgery
A foundational requirement is that a patient must be at least 18 years old. Since the eye continues to grow throughout adolescence, performing the procedure before the eye has fully matured may lead to a regression of the correction. Stability of the refractive error is a primary consideration, requiring the vision prescription to have remained unchanged for a minimum of 12 months. This stability confirms the underlying eye structure is no longer fluctuating significantly.
The patient’s expectations must also align with realistic outcomes. Laser eye surgery can dramatically improve vision, but it does not guarantee perfect 20/20 vision for every individual. Understanding that the goal is to reduce reliance on corrective lenses helps manage post-operative satisfaction. Patients must also comply with instructions for pre-operative preparation and post-operative care to ensure proper healing.
Eye Health Requirements and Limitations
Laser vision correction treats common refractive errors, which are problems with how the eye focuses light. These errors include myopia, hyperopia, and astigmatism. The procedure works by adjusting the curvature of the cornea to change its focusing power.
Corneal thickness is a critical measurement that determines the safety of the procedure, particularly for LASIK. A key safety metric is the residual stromal bed, the amount of tissue remaining beneath the surgical area after correction.
Most surgeons aim to leave a residual stromal bed of at least 250 to 300 µm to maintain the structural integrity of the cornea and prevent ectasia. Since the laser removes tissue, patients with thinner corneas or very high prescriptions may not have enough tissue left for safe LASIK, making PRK a better option.
Refractive error limits also apply, as treating a higher prescription requires removing a greater volume of corneal tissue. For myopia, the upper limit is generally around -12.00 diopters, and for hyperopia, it is typically around +6.00 diopters. Astigmatism correction is usually limited to about 6.00 diopters. Prescriptions outside of these ranges may not be fully correctable or may increase the risk of complications.
Medical Conditions That Prevent Treatment
Certain systemic health factors can interfere with the eye’s ability to heal, making them a temporary or permanent contraindication. Individuals with autoimmune disorders, such as lupus or rheumatoid arthritis, may have a compromised healing response. This increases the risk of corneal haze, delayed recovery, or other complications following the laser treatment.
An immunocompromised state, whether due to disease or medication, raises the risk of post-operative infection. Uncontrolled diabetes also affects eligibility, as fluctuating blood sugar levels impair the body’s healing capacity and cause temporary vision changes.
Hormonal changes require a delay in treatment because they temporarily alter vision stability. Women who are pregnant or nursing must postpone surgery until several months after breastfeeding has finished. Hormonal shifts can cause temporary changes in corneal shape, leading to inaccurate measurements and unsatisfactory surgical results.