To qualify for LASIK, you need a stable prescription, corneas thick enough to safely reshape, healthy eyes free of certain conditions, and you must be at least 18 years old. Most people who want LASIK are eligible, but the screening process is thorough. Here’s what surgeons actually evaluate and what could rule you out.
Your Prescription Must Fall Within Treatable Limits
LASIK works by reshaping your cornea to correct how light enters your eye, so there are limits to how much correction the laser can safely perform. For nearsightedness, most systems treat up to about -12.0 diopters. Farsightedness can be corrected up to +6.0 diopters. Astigmatism is treatable up to 5.0 or 6.0 diopters, depending on whether it occurs alone or alongside nearsightedness or farsightedness.
If your prescription exceeds these ranges, you may still have options like implantable lenses, but standard LASIK won’t be on the table. A newer procedure called SMILE treats nearsightedness up to -10.0 diopters with up to 3.0 diopters of astigmatism.
Your Prescription Needs to Be Stable
Surgeons want to see that your vision hasn’t changed significantly for at least one year before surgery. If your prescription is still shifting, correcting it with LASIK would be like hitting a moving target. You’d end up needing glasses again shortly after the procedure. This is one reason the minimum age is typically 18, though many surgeons prefer patients to be in their mid-20s, when prescriptions are more likely to have settled.
Your Corneas Must Be Thick Enough
This is one of the most important structural requirements. LASIK involves creating a thin flap on the surface of your cornea, then using a laser to remove tissue underneath. After the procedure, the remaining corneal tissue (called the residual stromal bed) needs to be at least 300 microns thick to maintain structural integrity. Most surgeons previously accepted 250 microns as the minimum, but 300 is now considered the safer standard to prevent the cornea from weakening and bulging outward after surgery.
The flap itself is typically 100 to 120 microns thick. So your surgeon calculates: starting corneal thickness, minus flap thickness, minus the amount of tissue the laser needs to remove for your prescription. If the math doesn’t leave enough cornea behind, you won’t qualify. This is why people with high prescriptions and naturally thin corneas are often turned down. Your corneal thickness is measured during your screening exam using a painless mapping test called pachymetry.
What the Screening Exam Involves
The qualification process centers on a detailed evaluation called corneal topography. This test creates a three-dimensional map of your cornea’s surface, measuring its curvature, elevation, and thickness at every point. It’s painless and takes only a few minutes, but it gives your surgeon critical information: whether your cornea has an irregular shape that could cause complications, whether it’s thick enough for safe treatment, and whether there are early signs of conditions like keratoconus (a progressive thinning and bulging of the cornea that makes LASIK dangerous).
Your surgeon will also measure your pupil size, check your eye pressure, evaluate your tear film for dry eye, examine your retina, and test your overall eye health. The entire evaluation typically takes one to two hours.
Contact Lenses Before Your Evaluation
If you wear contacts, you’ll need to switch to glasses before your screening appointment. Contact lenses temporarily reshape your cornea, which can throw off the measurements your surgeon needs. For soft lenses, plan to stop wearing them at least two weeks before surgery. Rigid gas permeable lenses require at least three weeks, sometimes longer. Some surgeons will let you wear contacts up to the day of your initial consultation, but you’ll still need to go without them for a set period between that visit and your actual procedure date.
Eye Conditions That Can Disqualify You
Several eye-specific conditions can prevent you from qualifying. The FDA lists these as concerns during screening:
- Keratoconus: a condition where the cornea thins and bulges into a cone shape. LASIK would make it worse.
- Severe dry eye: LASIK temporarily reduces tear production, so starting with already dry eyes can lead to significant discomfort and healing problems.
- Glaucoma or elevated eye pressure: the suction applied during flap creation can be risky, and some glaucoma medications affect healing.
- Recurring eye infections: a history of herpes simplex or herpes zoster (shingles) affecting the eye area raises the risk of reactivation after surgery.
- Uveitis or iritis: chronic inflammation inside the eye can flare up after the procedure.
- Previous eye surgeries: prior LASIK, PRK, or radial keratotomy may make additional correction inadvisable.
- Blepharitis: chronic eyelid inflammation increases infection risk after surgery.
Health Conditions That Affect Eligibility
Your overall health matters too, because LASIK requires your body to heal properly. Uncontrolled diabetes can impair wound healing and is a disqualifying factor. Autoimmune and connective tissue disorders are a particular concern. The American Academy of Ophthalmology lists uncontrolled autoimmune disease as a contraindication, and even controlled autoimmune conditions are considered relative contraindications, meaning they raise risk but don’t automatically rule you out.
Specific conditions that fall into this category include rheumatoid arthritis, lupus, Sjögren’s syndrome, psoriatic arthritis, and ankylosing spondylitis. These diseases can cause abnormal healing responses in the cornea. Being on immunosuppressive medications also raises concern because of increased infection risk. If you have one of these conditions, your surgeon and rheumatologist may need to evaluate your situation together.
HIV and other immunodeficiency states are also flagged by the FDA as conditions that may prevent proper healing.
Pregnancy and Hormonal Changes
Hormonal fluctuations during pregnancy and breastfeeding can temporarily change your prescription and affect corneal thickness and tear production. Most surgeons recommend waiting at least three to six months after delivery, and until you’ve finished breastfeeding, before even scheduling a LASIK evaluation. Getting screened while your hormones are still in flux could produce inaccurate measurements and lead to an under- or over-correction.
Pupil Size Is Less of a Concern Than It Used to Be
For years, patients were told that large pupils (typically above 7 mm in dim light) would disqualify them due to increased risk of glare, halos, and starbursts at night. This concern has largely been reconsidered. Two large studies found that pupil size alone was not a significant risk factor for night vision problems after laser vision correction. Modern wavefront-guided treatments create larger, more customized treatment zones that reduce these symptoms even in patients with very large pupils. The amount of correction matters more than pupil size: someone with mild nearsightedness and large pupils may have less risk of night vision issues than someone with moderate nearsightedness and average pupils.
Your surgeon will still measure your pupils, but a large reading alone is unlikely to disqualify you with current technology.
What Happens If You Don’t Qualify
If LASIK isn’t right for you, your surgeon will typically discuss alternatives during the same visit. PRK is a surface-based procedure that doesn’t require a flap, making it an option for people with thinner corneas. Implantable lenses work for prescriptions that exceed LASIK’s treatable range. Refractive lens exchange replaces your natural lens entirely and is sometimes recommended for older patients. Not qualifying for LASIK doesn’t mean you’re out of options for reducing your dependence on glasses or contacts.