Laser surgery can correct refractive errors of vision, including nearsightedness, or myopia; farsightedness, or hyperopia; and astigmatism, an unevenness of the cornea. Photoreactive keratectomy, or PRK, the most common type of corrective laser eye surgery before the debut of LASIK, is still the corrective surgery of choice for the military and for people with thin corneas and other corneal issues, the Encyclopedia of Surgery reports. PRK, unlike LASIK, is a flapless procedure, meaning the top layer of corneal cells is removed so the cornea can be reshaped. Like any surgery, PRK has side effects, some serious.
Pain
Because the top layer of cells is scraped off the cornea, PRK causes more pain after surgery than flap procedures such as LASIK, which leave the top layer of cells in place by creating a flap to work beneath. Pain severe enough to require narcotics may occur after PRK, unlike LASIK, which usually causes little discomfort after surgery. Epithelial healing can take three to five days to resolve, LASIK MD states, during which the eye remains scratchy and uncomfortable.
Vision Changes
Night glare, causing halos around lights and haze, often affects vision after PRK. Night vision problems may occur more often in people over age 50, people with high myopia, and those with residual refractive errors after surgery. Haze, one of the most problematic complications of flapless surgeries like PRK, according to LASIK MD, has become less common with newer lasers and surgical techniques. Rapid healing can leave corneal scars that contribute to haze.
Because the scraped off epithelial cells must grow back, vision fluctuates for as long as six months after PRK, the Encyclopedia of Surgery warns. Around 80 percent of people have vision improvement at one month post surgery, compared to almost immediate improvement after LASIK. Around 90 percent of people have 20/20 vision a year after PRK with corrective lenses, and 95 to 98 percent have vision 20/40 or better, the Cleveland Clinic states.
Dry Eye
Dry eye occurs less frequently after PRK than after flap procedures such as LASIK, but PRK patients still often require use of artificial tears after surgery. Dry eye occurs because of disruption of corneal nerve fibers, which gradually grow back, according to LASIK MD.
Infection
Infection can occur after any surgery, but more commonly occurs after PRK than LASIK due to the complete removal of the epithelial layer of cells from the cornea, the Encyclopedia of Surgery notes. Antibiotics eye drops used after surgery reduce the risk of infection.
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