Laser eye surgery works well for most adults with stable prescriptions, but not everyone is a good candidate. Your age, prescription strength, corneal thickness, overall health, and even your job all factor into whether the procedure is right for you. More than 90 percent of patients achieve 20/20 vision or better after LASIK, and 96 percent report satisfaction, but those numbers reflect carefully screened candidates, not the general population.
The Basic Requirements
You need to be at least 18, though most surgeons prefer patients to be in their mid-20s when the eyes have fully matured. The most important prerequisite is a stable prescription. If your glasses or contacts prescription has changed in the past year or two, surgery performed on a moving target is more likely to leave you needing correction again. Your surgeon will compare recent eye exams to confirm your vision has leveled off.
Each type of laser eye surgery covers a specific range of prescriptions. LASIK is FDA-approved for nearsightedness up to about minus 8 diopters and farsightedness up to plus 6, with astigmatism correction up to 3 diopters. SMILE, a newer procedure, handles nearsightedness from minus 1 to minus 10 and astigmatism up to 3 diopters but doesn’t treat farsightedness. Surface-level procedures like PRK can correct nearsightedness up to roughly minus 9.75 diopters and farsightedness up to plus 6. If your prescription falls outside these ranges, you may need a different approach entirely, such as an implantable lens.
Corneal Thickness and Shape
Laser eye surgery reshapes the cornea to correct your vision, so you need enough corneal tissue to work with. During a LASIK consultation, your surgeon maps the thickness and curvature of your cornea in detail. The procedure creates a thin flap and then removes tissue underneath, so both the flap and the remaining tissue (called the residual stromal bed) need to be thick enough to maintain structural integrity. Surgeons generally aim to leave at least 275 to 300 microns of tissue beneath the flap.
If your corneas are too thin for LASIK, PRK is often an alternative. Because PRK doesn’t create a flap, it preserves more tissue. Corneal shape matters too. Conditions like keratoconus, where the cornea progressively thins and bulges into a cone shape, are a firm contraindication. Irregular corneal topography increases the risk of a serious complication called ectasia, where the cornea weakens and distorts after surgery.
Health Conditions That Rule You Out
Several systemic diseases can interfere with how your eyes heal after surgery. The FDA specifically flags autoimmune conditions like lupus and rheumatoid arthritis, immunodeficiency states including HIV, and diabetes. These conditions can slow or complicate wound healing, raising the risk of poor outcomes. Certain medications create similar problems. Long-term steroid use and drugs containing retinoic acid (commonly prescribed for severe acne) can impair the cornea’s ability to recover.
Eye-specific conditions also matter. Chronic dry eye is one of the most common reasons people are deferred from surgery. Before clearing you, your surgeon will assess tear production and tear film stability. If your tears break apart on the surface of your eye in under five seconds, or if a strip test shows very low tear output, you likely have dry eye that needs treatment first. This is especially relevant if you’ve worn contact lenses for many years or have a high prescription, both of which are linked to higher rates of pre-existing dry eye. In many cases, treating the dryness for a few months makes surgery possible later.
Active eye infections, significant cataracts, glaucoma, and a history of herpes simplex affecting the eye are additional red flags your surgeon will screen for.
Why Pupil Size Matters
If your pupils dilate very wide in dim light, you face a higher risk of night vision problems after surgery. Research has found a significant correlation between large pupil size in darkness and post-LASIK complaints like halos, starbursts, and glare around lights. This happens when dilated pupils extend beyond the zone of corrected cornea, allowing untreated areas to scatter incoming light. A thorough preoperative exam includes measuring your pupils in low-light conditions. People with very large pupils aren’t necessarily disqualified, but they should understand the tradeoff and discuss newer laser platforms that use wider treatment zones.
Options After Age 40
Starting around your early to mid-40s, the lens inside your eye gradually loses flexibility, making it harder to focus on close objects. This natural process, called presbyopia, affects everyone and changes the calculation around laser eye surgery. Standard LASIK corrects distance vision beautifully, but it won’t prevent you from needing reading glasses.
One workaround is monovision, where the surgeon intentionally corrects one eye for distance and the other for near vision. The near eye is typically targeted to about minus 1 to minus 2.25 diopters of nearsightedness. Your brain learns to rely on whichever eye has the clearer image for a given task. Studies show no correlation between a patient’s age or the specific near target and their satisfaction with the result. The key is trying it before committing. Most clinics will have you test monovision with trial lenses in the office or with contact lenses for a few days at home. If the imbalance feels natural, you’re likely a good candidate. If it gives you headaches or feels disorienting, a different approach, like multifocal lens implants, may suit you better.
People in this age group who’ve never needed glasses face a unique situation. They’re used to perfect unaided distance vision, so expectations run high. Surgeons pay particular attention to counseling these patients, since monovision intentionally blurs one eye at distance to gain near vision.
How Your Job and Lifestyle Factor In
LASIK creates a corneal flap that heals in place but never bonds back with the same strength as untouched tissue. For most people this is clinically irrelevant, but if you’re in a profession or sport where direct eye trauma is a real possibility, that flap can be a vulnerability. Military personnel, law enforcement officers, MMA fighters, and boxers are often steered toward PRK instead. The U.S. military’s refractive surgery program uses PRK as the standard for combat-eligible service members precisely because it doesn’t involve a flap.
PRK does come with a longer recovery. While LASIK patients typically see clearly within a day, PRK patients deal with discomfort and blurry vision for several days to a week, with full visual stabilization taking a few weeks to a couple of months. Activity restrictions after PRK, including no swimming, contact sports, or vigorous exercise, usually last several weeks. If your schedule can’t accommodate that downtime, LASIK’s faster recovery may be the better practical choice, assuming your risk profile allows it.
The Ideal Candidate Profile
The people who benefit most from laser eye surgery share a cluster of traits: they’re at least in their early to mid-20s (or older), have had a stable prescription for at least a year, have adequately thick and normally shaped corneas, produce healthy tears, have no autoimmune or healing-related conditions, and have realistic expectations about the outcome. Ninety-nine percent of well-screened patients achieve 20/40 vision or better, the threshold for driving without glasses in most states, and over 90 percent reach 20/20.
If you’ve been told you’re not a candidate for one type of procedure, it’s worth asking about alternatives. Someone with thin corneas who can’t have LASIK may do perfectly well with PRK. Someone whose prescription is too high for any corneal procedure might be a candidate for an implantable contact lens. The consultation itself, which involves detailed corneal mapping, tear film testing, pupil measurement, and a full medical history review, is the only way to get a definitive answer.