LASIK is one of the most popular elective procedures in the United States. Performed about 600,000 times annually, the refractive surgery corrects several vision conditions, helping the majority of patients achieve between 20/20 and 20/40 vision. So it would seem that when it comes to LASIK, ideal candidates are plentiful.

That assumption is both right and wrong. Many thousands of people qualify for LASIK every year. However, there are a number of eligibility requirements that help ensure the eye surgery’s safety and effectiveness.

How old do you have to be to get LASIK?

LASIK is FDA-approved for those aged 18 or older, but many ophthalmologists recommend waiting until your mid-20s, when your prescription is less likely to change. Most procedures are performed on patients between the ages of 20 and 40.

Around age 40, your vision begins to change again due to presbyopia, or age-related farsightedness. It causes middle-aged and older people to need reading glasses—even successful eye-surgery patients have to deal with it as they age. LASIK cannot treat presbyopia, so fewer older people opt to get the surgery. However, as long as your eyes remain healthy and otherwise suitable, you can qualify for the procedure well into your 70s.

What are the LASIK eye surgery requirements?

Eyes of suitable quality

A consultation with an eye doctor will tell you if you’re an ideal candidate for LASIK. During a preoperative exam, the doctor will take detailed measurements of your cornea. Because the surgery revolves around reshaping the cornea (often by ablating microscopic amounts of tissue), it requires healthy corneas of normal thickness. Performing LASIK on corneas that are too thin or misshapen can result in complications.

No preexisting conditions

There are a few conditions that could prevent you from being eligible, including chronic dry eye, glaucoma, cataracts, eye infections or injuries, diabetes, and autoimmune disorders. While some of these will merely delay your surgery until they’re treated, others will exclude you altogether. Also, if you’re pregnant, breastfeeding, or taking medication that affects your vision, you’ll have to wait until your prescription stabilizes.

Vision within a certain range

The eye surgery is most effective on prescriptions within certain limits. This prescription must be stable for at least one year; many doctors prefer two. The following measurements of correction needed to restore normal vision (diopters) are similar to the prescription that appears on your contact-lens boxes:

• LASIK for nearsightedness: Most doctors treat nearsightedness of up to -9D or -10D.
• LASIK for farsightedness: Most doctors treat farsightedness of up to +4D or +5D.
• LASIK for astigmatism: Most doctors treat astigmatism of up to 8D.

Those with higher prescriptions might be candidates for other forms of vision correction—read about two below.

How much does LASIK cost?

Surgeons charge per eye, and the cost can vary based on a variety of factors, such as your prescription and the equipment used. TLC Laser Eye Centers says to expect standard prices of about $2,000 per eye. But remember, LASIK is a medical procedure, which means that all sorts of financial help is available. Look into tax-exempt savings accounts such as FSAs and HSAs, or contact your insurance company to see if it offers a discount.

Are there other vision-correction procedures besides LASIK?

If you don’t qualify for LASIK, you aren’t necessarily doomed to glasses forever. There are additional options:

PRK laser eye surgery

PRK, or photorefractive keratectomy, is a predecessor to LASIK and therefore very similar. The primary difference is that there is no corneal flap created during PRK. Instead, the cornea’s entire outer epithelial layer is removed before a laser alters its stromal layer. This leads to a longer, more painful recovery time as the epithelial layer grows back, but the end results are similar.

Also, PRK is suitable for those with thinner corneas or those who would be at risk for flap complications if they got LASIK. (That latter group includes people who are involved in contact sports and other activities where they could be hit or poked in the eye.)

Implantable contact lenses

These work to correct nearsightedness exactly like regular contacts, except from within your eye rather than on its surface. (Clinical trials are ongoing for approval to treat farsightedness.) Implantable lenses are good for patients who are too nearsighted to qualify for LASIK or PRK as they can correct up to -20D of nearsightedness.