The short version: About 85% of people who want LASIK are good candidates. The key requirements are a stable prescription, adequate corneal thickness, healthy eyes, and being at least 18 years old (21+ is preferred). This guide covers every requirement and disqualifier so you know where you stand before booking a consultation.
The Core Requirements
Stable Prescription
Your glasses or contact lens prescription should have been stable — meaning no significant change — for at least 12 months. "Significant change" means ±0.50 diopters or more. If your prescription is still shifting, LASIK results will be temporary because your eye is still changing shape.
Prescription Range
LASIK can correct a wide range of refractive errors, but there are limits:
| Condition | Typical Correction Range | Notes |
|---|---|---|
| Myopia (nearsightedness) | Up to −12.00 diopters | Most common LASIK candidate |
| Hyperopia (farsightedness) | Up to +6.00 diopters | Fewer candidates; PRK may be preferred |
| Astigmatism | Up to 6.00 diopters | Can be corrected alone or with myopia/hyperopia |
Prescriptions beyond these ranges may still be treatable with ICL (implantable contact lenses), which are available at Medellín clinics.
Corneal Thickness
LASIK works by removing corneal tissue. Your cornea needs to be thick enough to safely reshape while maintaining structural integrity. The general minimum is 500 microns (0.5mm), though this depends on how much correction is needed. Thinner corneas may be candidates for PRK or ICL instead.
Your corneal thickness is measured during your pre-operative exam with pachymetry — you cannot know this measurement without being examined.
Age
You must be at least 18 for LASIK (FDA requirement). However, most surgeons prefer patients to be 21+, because prescriptions tend to stabilise in the early 20s. There is no upper age limit for LASIK, though patients over 40 need to understand presbyopia (more on this in our LASIK After 40 guide).
General Eye Health
Your eyes should be free of active disease. Conditions like severe dry eye, active infections, corneal scarring, advanced glaucoma, and uncontrolled cataracts need to be addressed before considering LASIK.
Conditions That May Disqualify You
Keratoconus
Keratoconus is a condition where the cornea thins and bulges into a cone shape. LASIK can make keratoconus worse, which is why pre-operative corneal topography screening is critical. Even forme fruste keratoconus (a mild, early form) is typically a contraindication. If you have keratoconus, ICL or corneal cross-linking may be options — discuss with your surgeon.
Severe Dry Eye
LASIK temporarily worsens dry eye because the procedure cuts corneal nerves that trigger tear production. If you already have moderate-to-severe dry eye syndrome, LASIK can make it significantly worse. Mild dry eye, however, is usually manageable with artificial tears and does not automatically disqualify you. PRK and SMILE both produce less dry eye than LASIK.
Autoimmune Disorders
Conditions like rheumatoid arthritis, lupus, Sjögren's syndrome, and type 1 diabetes can impair wound healing and increase the risk of complications. These are not absolute disqualifiers, but they require careful evaluation and may steer your surgeon toward a more conservative approach.
Pregnancy and Nursing
Hormonal changes during pregnancy and breastfeeding can temporarily alter your prescription. Most surgeons require you to wait at least 3 months after stopping nursing before performing LASIK, to ensure your prescription has restabilised.
Before flying to Medellín for LASIK, you can get a preliminary candidacy assessment from your local eye doctor. Request a basic exam including prescription verification, corneal topography, and dry eye evaluation. This will not replace the Medellín surgeon's exam, but it will tell you if there are obvious disqualifiers.
The Pre-Operative Exam in Medellín
Your candidacy is ultimately determined during the comprehensive exam on Day 1 of your trip. This exam typically lasts 90 minutes to 2 hours and includes:
- Corneal topography — maps the curvature of your cornea in detail
- Pachymetry — measures corneal thickness at multiple points
- Wavefront analysis — maps the unique optical characteristics of your eye
- Pupil size measurement — large pupils increase the risk of halos/glare
- Dilated fundus exam — checks retinal health
- Tear film assessment — evaluates dry eye severity
- Refraction — confirms your exact prescription
Stop wearing soft contact lenses at least 3 days before your exam (2–3 weeks for rigid gas-permeable lenses). Contacts alter your corneal shape, and wearing them up to the exam will produce inaccurate measurements.
What Happens If You Are Not a Candidate?
Being told "no" is not a dead end. It means LASIK specifically is not the safest option for your eyes. Alternatives available in Medellín include:
- PRK — for thin corneas or flap-related concerns
- SMILE — for myopia patients with dry eye concerns
- ICL (Implantable Collamer Lens) — for very high prescriptions or thin corneas
- Refractive Lens Exchange — for patients over 50 who also have early cataracts
A surgeon who tells you that you are not a LASIK candidate but offers an appropriate alternative is doing their job well. A surgeon who insists everyone is a candidate is not.
Not Sure If You Qualify?
Send us your current prescription and any concerns. We will give you an honest preliminary assessment before you book a flight.
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