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PRK (or photorefractive keratectomy) is the original laser vision correction procedure. It received FDA approval for use in the United States in 1995, a few years before LASIK.
Though LASIK has surpassed PRK as the most popular vision correction surgery, PRK remains a very viable procedure for the correction of nearsightedness, farsightedness and astigmatism.
PRK vs. LASIK
In both LASIK and PRK, an excimer laser is used to reshape the cornea and correct refractive errors. The difference between the two procedures is what happens before the laser treatment.
In PRK, only the clear outer layer of the cornea (called the epithelium) is removed prior to the laser reshaping. This epithelium generally grows back within a few days after surgery.
In LASIK, a corneal flap containing both the epithelium and underlying corneal tissue (called the stroma) is created. The flap remains attached to the eye by a small hinge and is replaced after the excimer laser treatment. The flap acts like a living bandage, and enables faster vision recovery after surgery. It also reduces post-operative discomfort while the eye is healing.
Though LASIK is more popular than PRK because of these features, PRK has its own distinct advantages. Because there is no corneal flap created during PRK, there is no risk of a flap complication after surgery. Also, PRK often can be performed on corneas that may be too thin for LASIK surgery.
Numerous studies have shown that the long-term visual outcomes of PRK and LASIK are essentially the same.
Before PRK Surgery
Prior to PRK surgery, your eye doctor will examine your eyes to determine the health of your eyes and exactly what kind of vision correction you need.
An instrument called a corneal topographer may be used to create a "map" of your cornea that displays the curvature of your eye and irregularities that the surgeon must address. Also, wavefront-guided measurements that are used for custom LASIK may be used to create a PRK treatment that reduces higher-order aberrations for optimum visual acuity.
Your eye doctor will ask you about any medical conditions you have. Some conditions may disqualify you altogether as a PRK candidate; others may mean a postponement of the procedure or special care afterward.
During PRK Surgery
PRK is an ambulatory procedure: you walk into the surgery center, have PRK, and walk out again. The actual surgery only takes a few minutes, and you're awake the whole time. Occasionally, the doctor will give a mild oral sedative beforehand.
The basic steps in PRK surgery are:
- Anesthetic eye drops are applied to the eye to prevent discomfort during surgery.
- A device is placed under the eyelids to keep the eye wide open.
- The central epithelium is removed — either manually (after being softened with a dilute alcohol solution) or with a laser.
- The excimer laser is positioned over the eye and activated to reshape the cornea.
After the laser treatment is finished, medicated eye drops are applied to the eye to prevent infection and reduce inflammation. A non-prescription contact lens then is applied to the eye to serve as a bandage during the initial healing period after surgery.
Your doctor also will prescribe medication to control any post-operative pain, but many people feel no more than mild discomfort or "scratchiness" afterward.
Immediately after PRK, you will rest for a little while. Unlike LASIK, which nearly always is performed on both eyes the same day, PRK often is performed on each eye separately, about a week or two apart. This allows time to ensure the first eye has achieved good vision before the second eye is treated.
You can go home shortly after the procedure, but someone else must drive. At home, you should relax for at least a few hours.
As with any kind of eye surgery, it is important that you follow your doctor's instructions to the letter. Get plenty of rest and call your doctor immediately if you suspect a problem.
You may be able to go to work the next day, but many doctors advise a couple of days of rest instead. You also should avoid strenuous exercise for up to a week.
Two or three days after surgery, after the epithelium has had a chance to grow back, the bandage contact lens is removed. Typically, you will continue to use anti-inflammatory medications for several weeks after surgery.
Visual Outcomes After PRK
Most people see 20/20 or better after PRK, as clearly as they would after LASIK.
But vision recovery takes longer after PRK, and it may be three to six months before optimum vision is attained. In some cases, prescription glasses may be needed temporarily until healing progresses and vision improves.
If you are over age 40, it is likely you will still need to wear reading glasses after PRK.
PRK Risks and Complications
As with LASIK, there are risks and potential complications associated with PRK. These include:
- Dry eyes
- Glare, starbursts and/or halos when driving at night
- Incomplete or inaccurate vision correction
- Infection after surgery
But serious complications during and after PRK are rare, and following your eye doctor's instructions will decrease your risk of any problems.
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