LASIK is a type of refractive surgery. This kind of surgery uses a laser to treat vision problems caused by refractive errors. You have a refractive error when your eye does not refract (bend) light properly.
For you to see clearly, light rays must travel through your cornea and lens. The cornea and lens refract the light so it lands on the retina. The retina turns light into signals that travel to your brain and become images. With refractive errors, the shape of your cornea or lens keeps light from bending properly. When light is not focused on the retina as it should be, your vision is blurry.
With LASIK, your ophthalmologist uses a laser to change the shape of your cornea. This laser eye surgery improves the way light rays are focused on the retina. LASIK is used to treat myopia (nearsightedness), hyperopia (farsightedness) and astigmatism.
The goal of LASIK is to correct your refractive error to improve your vision. LASIK eye surgery may reduce your need for eyeglasses or contact lenses. In some cases, it may even allow you to do without them completely.
Who Is a Good Candidate for LASIK Surgery?
To have LASIK surgery, you need to meet certain requirements. Here are some of them:
- You should be 18 years or older (ideally, over 21 years old, when vision is more likely to have stopped changing).
- Your eye prescription should not have changed much in the last year.
- Your refractive error must be one that can be treated with LASIK.
- Your corneas need to be thick enough and healthy, and your overall eye health must be generally good.
- You need to have realistic expectations about what LASIK can and cannot do for you.
Some people are not candidates for LASIK. They include people with:
- an unstable (changing) refractive error
- extreme levels of myopia, hyperopia or astigmatism
- severe dry eye
- corneas that are too thin
- corneal scars or disease
- keratoconus (cone-shaped cornea)
- advanced glaucoma
- a cataract affecting vision
- a history of having certain eye infections
- diabetes that is not controlled well
Also, women who are pregnant or breastfeeding should not have LASIK. This is due to vision changes that can happen during pregnancy.
Your ophthalmologist can talk with you about other conditions that may keep you from having LASIK.
To determine whether you are a candidate for LASIK, your ophthalmologist will examine your eyes. Here is what will be done:
- The overall health of your eyes will be checked.
- Measurements of your cornea will be taken.
- Your pupil size will be checked.
- Your refractive error will be measured.
In some cases, your ophthalmologist will measure the quality and the amount of tears that your eyes make. This is to check if you have dry eye, and if so, how severe it is.
What to Expect With LASIK
Before the laser eye surgery
You and your ophthalmologist will discuss your vision needs based on your lifestyle. For example, if you play sports, you may be seeking clear distance vision from surgery.
Also, you and your ophthalmologist should discuss your expectations for LASIK. People who have LASIK to achieve perfect vision without glasses or contacts run the risk of being disappointed. This laser eye surgery allows people to do most of their everyday tasks without corrective lenses. However, you might need to wear glasses for certain activities, such as reading or driving at night.
Your ophthalmologist will thoroughly examine your eyes and make sure you are a candidate for LASIK. Here is what he or she will do:
- Test your vision. This is to make sure that your vision has not changed. It also shows how high your refractive error is and whether LASIK can be used to correct your vision.
- Check for other eye problems. Your ophthalmologist will make sure that you do not have eye problems. This is because other problems could affect your surgery, or LASIK could make those other problems worse. For example, if you have dry eyes, they may be worse after LASIK.
- Measure and map the surface of your cornea. Your ophthalmologist will check the thickness of your cornea and make precise measurements of the cornea’s surface. Your eye surgeon uses these measurements to program the computer-based laser used during surgery.
- Measure your pupil size. He or she will also measure the size of your pupil. If your pupil is very large, you could see halos (rings of light) at night after LASIK.
This laser eye surgery is done in an outpatient surgery center or your ophthalmologist’s office. Your eye surgeon uses a laser to reshape your cornea. Here is what to expect:
- Your eye will be numbed with eye drops.
- Your eye surgeon will place an eyelid holder on your eye to keep you from blinking. They will also place a suction ring on your eye to keep it from moving. You will feel pressure like a finger pressing firmly on your eyelid. At this point, your vision will go dim or black.
- Using either a device called a microkeratome or a laser, your ophthalmologist makes a paper-thin flap in the cornea tissue. Then they lift and fold the flap back.
- You will be asked to stare at a target light so that your eyes will not move. The ophthalmologist then reshapes your cornea using a laser. The laser is a special instrument that has been programmed with measurements for your eye.
- While your ophthalmologist is using the laser, you will hear a clicking sound. After reshaping the cornea, your eye surgeon folds the flap back down into position and smooths the edges. The flap attaches on its own in 2–3 minutes, where it will heal in place.
- The ophthalmologist may place a see-through shield over your eye or ask you to wear a shield while sleeping for a few days. This is to help protect your eye while it heals.
- You should plan to go home and take a nap or just relax after the surgery.
- For a few hours, your eyes may feel scratchy or feel like they are burning. You will be given special eye drops to reduce dryness and help your eye heal.
Vision after LASIK
About 9 out of 10 people (90%) who have LASIK end up with vision between 20/20 and 20/40—without glasses or contact lenses.
It is important to know that LASIK cannot correct presbyopia. This is the normal, age-related loss of close-up vision. With or without refractive surgery, almost everyone who has excellent distance vision will need reading glasses after around age 40.
To help with presbyopia, some people have LASIK to get monovision. This means one eye is left slightly nearsighted and the other eye is adjusted for distance vision. The brain learns to adapt so that the nearsighted eye is used for close work, while the other eye sees distant objects. Monovision is not for everyone. To see if you are able to adapt to this correction, you will probably want to try monovision with contact lenses first.
What Are the Risks of LASIK?
Like any surgery, LASIK carries risks of problems or complications you should consider.
Some people have side effects after LASIK that usually go away over time. However, in rare cases, they may not go away. For example, almost everyone who has LASIK will have dry eyes and changing vision during the day. These symptoms usually fade within a month. For some people, though, they may take longer to disappear or they may remain.
Other side effects, either temporary or permanent, could include:
Other rare risks include:
- eye infection
- worse vision than before LASIK, even with glasses or contacts (called loss of best-corrected vision)
Also, with LASIK, your vision may end up being under-corrected or over-corrected. These problems often can be improved with glasses, contact lenses, or additional laser surgery.
If you are happy wearing contacts or glasses, you may not want to have refractive surgery. Together, you and your ophthalmologist can weigh the risks and rewards of LASIK.
Considering LASIK? Learn more about this laser eye surgery
Before choosing to have LASIK, it's important to do your homework to ensure you are a good candidate, understand the potential risks and benefits, and have realistic expectations about what your vision will be like after surgery and for years to come. To ensure the best possible outcome, be a well-prepared and informed patient by reviewing the resources below before you have LASIK. If these materials raise any questions for you, be sure to discuss these questions with your ophthalmologist.
Is LASIK for Me? A Patient's Guide to Refractive Surgery (PDF 303K)
This guide, produced by the American Academy of Ophthalmology, offers straight-forward facts about what makes a good LASIK candidate, the risks and benefits of the surgery, how to choose a surgeon and an introduction to the informed consent process.
LASIK Surgery: Why All Patients Need the K Card (PDF 650K)
If you have decide to have LASIK, it is important to keep a record of your pre-operation and post-operation eye information. Your ophthalmologist may need this information if you have other eye surgery later, such as cataract surgery. Bring this "K Card" with you to your appointment with your ophthalmologist to have it completed and keep it for future use.
Questions to Ask When Considering LASIK
If you are considering LASIK, you should discuss with your ophthalmologist the benefits and risks — including quality of life issues — that could result from correcting vision with surgery rather than eyeglasses or contact lenses.