PRK (or photorefractive keratectomy) is a laser eye surgery similar to LASIK. Like LASIK, PRK involves the use of the cool (non-thermal) energy of the Excimer laser to re-shape the cornea and correct nearsightedness, farsightedness and astigmatism. It differs from LASIK in that no corneal flap is created prior to the laser treatment.
The U.S. Food and Drug Administration (FDA) first approved the Excimer laser for PRK in 1995---prior to its approval of the same laser for LASIK.
Though it generally takes PRK patients a longer time to achieve their best visual acuity (compared to LASIK patients), many refractive eye surgeons still prefer PRK over the more popular LASIK surgery.
What are the advantages of PRK over LASIK?
Though visual recovery is slower and there is more discomfort after PRK, it offers at least two advantages over LASIK:
1. The surgeon doesn't have to create a corneal flap during PRK. Therefore, PRK is a slightly easier procedure to perform and there is no risk of a flap complication.
2. PRK can be performed on thinner corneas. Since no corneal flap is required, more of the patient's corneal thickness is available for laser treatment.
What takes place during PRK?
The steps in the PRK procedure are usually as follows:
1. A few minutes before PRK, anesthetic eye drops are applied to the eye to numb the cornea and prevent discomfort during the procedure.
2. A small instrument is used to hold both eyelids open throughout the procedure.
3. The surgeon gently removes the thin, outer layer of corneal cells (called the epithelium) that has been softened with the anesthetic eye drops and/or a weak alcohol solution. This is performed manually with a surgical spatula or rotating brush.
4. After the epithelium has been removed, the Excimer laser is positioned over the center of the cornea. The laser changes the shape of the cornea by ablating (vaporizing) a tiny amount of corneal tissue. This part of the procedure takes less than one minute for most patients.
5. At the conclusion of the laser treatment, the surgeon will place a bandage contact lens on the eye for improved comfort after the procedure has been completed. This contact lens is left on the eye for a few days while the epithelium grows back over the surface of the cornea.
6. Antibacterial and anti-inflammatory eye drop medications are prescribed for use for a period of time after PRK to reduce the risk of infection and facilitate the healing process.
What happens after PRK?
Post-operatively, most PRK patients need to be evaluated by the surgeon or their eye doctor at the following milestones:
- Two to three months after PRK
- Four to six months after PRK
More frequent visits may be required, depending on your individual needs. The bandage contact lens can usually be removed 2 to 3 days after PRK, at which time the epithelium should be healed.
Most patients need to continue using medicated eye drops for 6 to 12 weeks after PRK. Some patients may need to continue to use the drops for up to 6 months or longer. (In general, patients who have higher amounts of nearsightedness or farsightedness treated with PRK will need to use medicated eye drops longer than patients who have mild refractive errors.)
Will my eyes hurt after PRK?
There is more eye discomfort after PRK than after LASIK. For a few days after the procedure, your eyes may be quite uncomfortable and sensitive to light. Usually these short-term problems can be managed with over-the-counter pain medicines (e.g. Tylenol(R)) and the use of sunglasses.
How long will it take for my vision to improve after PRK?
Visual recovery after PRK is generally slower than after LASIK. Though most people can perform routine tasks the following day, it may take a week or two after PRK before your eyesight is clear enough to drive. Your best vision after PRK may take up to six months.
Six months after surgery, visual outcomes of PRK and LASIK are quite comparable.
Are there any risks associated with PRK?
PRK and LASIK are popular because both surgical procedures have proven to be safe and effective. However, like any surgery, they are not risk-free. The primary post-operative risks associated with PRK are:
- Glare, halos or starbursts around lights at night
- Loss of some level of best corrected visual acuity
Fortunately, occurrences of sight-threatening corneal infections and loss of best corrected visual acuity are rare.
Who is a good candidate for PRK?
The best candidate for PRK (and LASIK) is someone who:
1. Has a mild or moderate amount of nearsightedness, farsightedness and/or astigmatism.
2. Is over 20 years old and hasn't had a change in their eyeglasses prescription for two years.
3. Desires to be less dependent on eyeglasses or contact lenses and has realistic expectations.
4. Is willing to accept the risks associated with the procedure.
5. Understands that a second treatment (called an enhancement) may sometimes be required to attain the desired level of visual acuity.