Photorefractive Keratectomy (PRK)
What is photorefractive keratectomy?
Photorefractive keratectomy (PRK) is a type of eye surgery to reduce nearsightedness (when you have trouble seeing distant objects clearly) and sometimes farsightedness (trouble seeing close objects clearly) and astigmatism (blurred vision at any distance). In this procedure an eye doctor removes very thin layers of tissue from the cornea. The cornea is the clear dome on the front of the eye.
How does it work?
Nearsightedness occurs when the eye is too long for the focus of the cornea. Light rays that normally focus on the retina (light-sensitive tissue at the back of the eye) focus in front of it. This causes images to appear blurry. Occasionally, nearsightedness occurs because your cornea is too steep. This also prevents the light rays from reaching the back of the eye.
During PRK the surgeon uses a laser to remove thin layers of tissue from the cornea. This changes the focus of the cornea so that light rays focus on or closer to the retina, which improves distance vision.
When is it used?
PRK is used to correct your distance vision and reduce your need for glasses or contact lenses. It is generally more successful for people who are somewhat nearsighted than for people who are very nearsighted. Be sure to talk to your doctor about your chances for improved vision.
Usually one eye is done at a time.
How do I prepare for the procedure?
Do not wear any makeup the day of surgery.
The surgery is done in your eye doctor's office. You will need to arrange for someone to take you home about an hour after the surgery. Allow for a few days to rest at home while your eye heals.
What happens during the procedure?
The doctor numbs your eye with special eyedrops. He or she scrapes away the epithelium, which is the outer layer of the cornea. Then the doctor uses a special laser to remove thin layers of the stroma (the next layer of the cornea), until it is the right shape to improve your vision.
What happens after the procedure?
Your eyes may hurt until the epithelium grows back. This takes about 3 to 7 days. Your vision may be hazy during this time. Ask your doctor about medicines to reduce your discomfort. Often a contact lens will be placed in your eye immediately after surgery to protect the surface of the eye and to help with the discomfort. Your doctor will remove the contact 3 or 4 days after the epithelium has healed.
Your vision may continue to change for several months.
What are the risks of PRK?
Your eye may become infected. Medicines and special contact lenses can cure infections and help your eye heal.
As with any surgery, the results are not guaranteed. Your eyes may be over-corrected, and you may become farsighted. Or they may not be corrected enough. Then you may still need glasses for best distance vision.
When your eyes heal, you may find that you need reading glasses for close vision. After PRK some people need to begin using reading glasses sooner than they would have without it. Remember that most people need reading glasses after about age 40 because of normal changes in their eyes.
Your eyes may become more sensitive to light. Also, you may see halos around lights or other unusual effects. These effects are due to light coming through the cut edges of the cornea. Some of these problems go away after your eyes heal, but some do not.
Be sure that you talk to your doctor about your risk of side effects.
What are the benefits of PRK?
After their eyes heal, many people (95% in some studies) have 20/40 vision or better after PRK. They do not need glasses or contacts for driving and many other activities.
Compared with RK (radial keratotomy), another type of surgery for nearsightedness, PRK removes tissue from the cornea to a fairly shallow depth. RK requires deeper cuts into the cornea. PRK avoids these deep cuts, which can weaken the eyeball.
If needed, your eye doctor can repeat the surgery to improve your vision.
When should I call my doctor?
Call your doctor immediately if you have:
- unusual pain
- a sudden loss of vision
- a lot of drainage from your eye.