Photorefractive Keratectomy (PRK)

• About the Surgery
• Risks
• Who ia a Candidate for PRK
• Treament
• Clinic Information
• Complete List of Surgical Procedures at Kellogg

About Photorefractive Keratectomy (PRK)
Photorefractive keratectomy (PRK) uses an excimer laser to reshape the cornea. (The "photo" in "photorefractive" refers to the light generated by the laser.) This laser procedure does not use incisions to reshape the cornea. Instead, it uses laser pulses to evaporate microscopic portions of the cornea so that it can change its shape in order to enhance vision. This type of surgery was approved for the treatment of nearsightedness in 1995.

Does it hurt?
No. For all refractive surgery procedures the eye is anesthetized before surgery using eye drops. Most people say they feel a slight amount of pressure when the laser is on, but absolutely no pain. There may be some pain during the healing process -- more for PRK than LASIK. That discomfort is treated with pain medication when necessary. Advances in technology and surgical technique have made refractive surgery more accurate and safe with the vast majority of patients having their vision corrected to 20/40 or better, although some patients may still need to wear glasses or contact lenses to achieve their best vision.

What's a laser?
Lasers focus a beam of light. There are different types of lasers whose energy is generated by various kinds of gases. The specific wavelengths of the light produced by the different gases affect different types of tissue. The excimer laser used for refractive procedures emits a "cold" light beam of light.

By mixing Argon and Fluoride gases together in an electrically charged cavity, the excimer laser produces a cool beam of highly precise ultraviolet laser. Instead of burning tissue, the excimer actually breaks the chemical bonds between the individual molecules of corneal tissue, all with little or no damage to surrounding cells. This process is known as photoablation, or vaporization using laser light.

By applying the laser's light beam to the surface of the cornea, the cornea is gently reshaped to focus light rays entering he eye directly on the retina.

How do you know where to focus the laser beam?
First we "map" your cornea so that we can see its exact shape as well as the microscopic hills and valleys on the surface. Using the computer in the laser and your refractive correction we develop a program of laser pulses to guide the refractive procedure. The computer will calculate the amount of energy needed and the exact placement of the beam to accomplish the amount of corneal correction so you can see clearly.

How long does the procedure take?
PRK for simple myopia or myopia with astigmatism generally takes less than 1 minute of laser use, requires no incisions, and is very precise. Each pulse of the excimer's laser light gently removes a microscopic layer of corneal tissue until the corrected curvature of the cornea is achieved. Total time for the procedure is approximately 15 minutes. Refractive surgery is done on an out-patient basis with most people returning to their normal activities within one to three days.

What's the difference between PRK and LASIK?
In PRK, the top layer of the cornea is removed so the surgeon can reshape the underlying cornea. In LASIK the ophthalmologist gets to the cornea by opening up a flap of the top layer, then performs the sculpting. Once the flap is returned to its original position, it protects the treated corneal tissue. The postoperative discomfort is usually shorter and vision returns faster with LASIK than with PRK.

How long does it take before my vision is improved?
With LASIK and PRK, you should see some improvement in the first few days after the surgery, with slight improvements over the next couple of weeks. The full effect will be achieved within 4-6 months after surgery. Note that some patients may still need to wear glasses or contact lenses following their procedure.