Mayo Clinic offers PRK refractive surgery

Thursday, August 19, 2004

When it comes to refractive surgery, everything old is new again. Dr. Akbar Hasan, a Mayo Clinic ophthalmologist, is performing photorefractive keratectomy (PRK), a laser vision correction procedure developed in the 1990s. The procedure was eclipsed by laser in-situ keratomileusis (LASIK), but thanks to improved technique, technology and patient evaluation, it is once again gaining popularity.

To perform PRK, the surgeon polishes off the skin (epithelium) of the cornea and uses an excimer laser — a "cool" laser that doesn't produce heat — to remove tissue from the surface of the cornea. The patient goes home with a contact lens, which acts as a bandage, on the treated eye. Blinking without the lens is uncomfortable, so it is worn for three-to-five days while the skin grows back.

In contrast, the surgeon performing LASIK reshapes the inner layers of the cornea with an excimer laser after creating a flap of corneal tissue that is folded back during the laser treatment. After the procedure, the flap is positioned back over the treated area. The incision to make the flap is made across the cornea with a precision cutting instrument. Healing progresses rapidly and with less discomfort than with PRK. However, compared to PRK, the procedure carries a small, but greater risk of problems associated with the corneal flap.

Most people with low-to-moderate correction necessary because of nearsightedness, farsightedness or astigmatism, are candidates for either procedure.

"With the older generation lasers in the mid-90s, people developed some corneal scarring with the PRK technique," Hasan says. "A lot of them were very, very nearsighted and required a large treatment, which resulted in some scarring. Because of the newer generation lasers, we don't see any scarring in low-to-moderately nearsighted people."

Hasan says patients' wariness over potential complications from LASIK also contributes to the renewed interest in PRK. Hasan performs both LASIK and PRK. He considers PRK safer.

"You have short term benefits with LASIK," Hasan says, "and in my opinion, long term benefits with PRK — also called surface ablation. With LASIK you do have to make an incision, which opens up the potential for some additional risk. It's not a high risk, but it is some additional risk. With PRK there is more corneal stability. There are no flap complications because there is no incision on the eye. The only downside is it takes longer to heal. Patients will probably have good vision in five-to-seven days and probably have great vision in three-to-four weeks. With LASIK they'll have good vision within a couple days and great vision within the week."

Hasan sees further refinements in refractive surgery. A hybrid procedure called laser epithelial keratomileusis (LASEK) combines the quicker healing and minimal discomfort of LASIK with the surface ablation of PRK. The key improvement will be saving the epithelial tissue that now sloughs off and is replaced by new tissue. "Eventually there will be a jet of water or plastic blade that will shave off the skin to keep it viable," Hasan says. "That will be the ideal situation."

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