1. Age
LASIK is FDA-approved for adults 18 and older. Many surgeons prefer to wait until the early to mid 20s, because eyes and prescriptions often keep changing into the 20s. There is generally no upper age limit, but age-related changes such as reading-vision decline and early cataracts become more relevant after 40 and especially after 60.

2. A stable prescription
LASIK corrects the prescription you have on the day of the exam. If your glasses or contact prescription has changed meaningfully in the past year or two, surgeons usually advise waiting. Many practices look for at least 12 months of stability, and some prefer longer.

3. A prescription within treatable range
Lasers are approved to treat limited ranges of nearsightedness (myopia), farsightedness (hyperopia), and astigmatism. The exact limits depend on the laser, and the commonly cited maximums are roughly:

• Nearsightedness: up to about -12 diopters

• Farsightedness: up to about +6 diopters

• Astigmatism: up to about 6 diopters

Many surgeons recommend other procedures well before a patient reaches those limits, because outcomes tend to be better with more moderate prescriptions. If your prescription is outside the range, options like PRK or implantable lenses may fit better. See our guide: LASIK vs PRK vs SMILE.

4. Healthy, thick-enough, regular corneas
LASIK removes a small amount of corneal tissue. If the cornea is too thin or has an irregular shape, the procedure can weaken it, and a serious complication called corneal ectasia (progressive bulging and distortion) becomes a concern. Corneal thickness is one of the most common reasons people are told LASIK isn't right for them. Surgeons measure thickness and map the cornea's shape at your exam. A thickness around 500 microns or more is often cited as a general benchmark, but the real calculation depends on your prescription and how much tissue would be removed.

5. Healthy eyes
Surgeons screen for conditions that raise risk or affect healing, including:

• Keratoconus or other corneal irregularities

• Significant or untreated dry eye

• Uncontrolled glaucoma

• Active eye infections or inflammation

• Corneal scarring or a history of serious eye injury

• Certain cataracts

Mild dry eye is common and doesn't always rule you out, but it may need treatment first, and it affects which procedure is best.

6. General health
Some health conditions and medications can affect healing or the stability of your vision. Be completely open with your surgeon about:

• Diabetes, especially if blood sugar isn't well controlled

• Autoimmune conditions such as lupus or rheumatoid arthritis

• Medications that may affect healing, including steroids and some acne medications

• Pregnancy or breastfeeding, which can cause temporary changes in vision. Surgeons usually advise waiting.

This is not a complete list. A full health history is part of the exam for a reason.

7. Realistic expectations
LASIK can greatly reduce your dependence on glasses or contacts, but it doesn't guarantee 20/20 vision, and it doesn't stop age-related reading changes. Many people still need reading glasses in their 40s and beyond. Some experience dry eyes, glare, or halos at night, especially in the first months. A good surgeon will discuss these openly.

What the candidacy exam involves