Laser Surgery - Elective Procedures May Correct Common Eye Disorders

Image of Laser Surgery

Although there are several types of surgical techniques being performed today to correct refractive errors, laser refractive correction is fast becoming the most technologically advanced method available, according to the American Academy of Ophthalmology in San Francisco. Doctors say laser surgery allows for an unparalleled degree of precision and predictability.


PRK

PRK is an outpatient procedure generally performed with local anesthetic eye drops. This type of refractive surgery gently reshapes the cornea by removing microscopic amounts of tissue from the outer surface with a cool, computer-controlled ultraviolet beam of light. The beam is so precise it can cut notches in a strand of human hair without breaking it, and each pulse can remove 39 millionths of an inch of tissue in 12 billionths of a second. The procedure itself takes only a few minutes, and patients are typically back to daily routines in one to three days.

Before the procedure begins, the patient's eye is measured to determine the degree of visual problem, and a map of the eye's surface is constructed. The required corneal change is calculated based on this information, and then entered into the laser's computer.

According to FDA's Center for Devices and Radiological Health, clinical studies showed that about 5 percent of patients continued to always need glasses following PRK for distance, and up to 15 percent needed glasses occasionally, such as when driving. In addition, many patients experienced mild corneal haze following surgery, which is part of the normal healing process. The haze appeared to have little or no effect on final vision, and could only be seen by a doctor with a microscope. Some patients experienced glare and halos around lights.

These conditions, however, diminished or disappeared in most patients in six months. For about 5 percent of patients, however, best-corrected vision without corrective lenses was slightly worse after surgery than before. In view of these findings, FDA and the Federal Trade Commission (which oversees advertising) issued a letter to the eye-care community in May 1996 warning that unrealistic advertising claims, such as "throw away your eyeglasses," and unsubstantiated claims about success rates could be misleading to consumers.

Lasik

LASIK is a more complex procedure than PRK. It is performed for all degrees of nearsightedness. The surgeon uses a knife called a microkeratome to cut a flap of corneal tissue, removes the targeted tissue beneath it with the laser, and then replaces the flap.

"With LASIK, the skill of the surgeon is important because he'll be making an incision," says Stephen Crawford, O.D., an optometrist practicing in Virginia, "compared to the PRK method where the machine does more of the work." Crawford urges people to find qualified, experienced doctors to perform this surgery. "You'll want someone who's done a number of LASIK procedures since this is a surgeon-dependent operation," he said.

According to Ken Taylor, O.D., vice president of Arthur D. Little, Inc., a technology and management consultant firm in Cambridge, Mass., "Last year, across the country, 40 to 45 percent of refractive surgeries performed by physicians were LASIK, which equates to approximately 80,000 procedures." Doctors not participating in clinical trials may choose to use the approved laser to perform LASIK procedures at their discretion, says Morris Waxler, Ph.D., chief of FDA's diagnostic and surgical devices section. But most uses are considered "off label" and are not regulated by FDA.

Ralph A. Rosenthal, M.D., director of FDA's division of ophthalmic devices, says, "The agency has ruled that individual physicians can perform LASIK under the general 'practice of medicine,' if it's in the patient's best interest."

Is lasik surgery for you?

For some, laser surgery has been the ultimate freedom from the everyday hassles of contact lenses, and a second chance at having normal eyesight. But can everyone expect such dramatic results?

"The answer is no," says Rosenthal. "It's not a foolproof procedure and people need to know that some can end up with worse eyesight than before they went in."

Mary Ann Duke, M.D., a general ophthalmologist practicing in Potomac, Md., adds that there are other reasons why the expectations for laser surgery vary from person to person. "People who are slow healers or who have ongoing medical conditions [such as glaucoma or diabetes] are not good candidates for laser surgery," she says. "That's why it's so important for patients to undergo a thorough examination with their doctor."

Poor candidates for this surgery also include those with uncontrolled vascular disease, autoimmune disease, or people with certain eye diseases involving the cornea or retina. Pregnant women should not have refractive surgery of any kind because the refraction of the eye may change during pregnancy.

Lasik: looking ahead

Currently, a number of other lasers for eye surgery are being tested in FDA-sanctioned studies to determine their safety and effectiveness. Investigational Device Exemptions (IDEs) filed with FDA allow for clinical studies involving the excimer laser and the correction of farsightedness. The IDE process is designed to investigate the safety and effectiveness of a device, or a new procedure with an already approved device, either to obtain information for publication or to generate the data needed to obtain marketing approval from FDA.

"If the refractive surgery center says the laser is approved by FDA, it probably is," Waxler concludes. "Still, it is wise for consumers to check that the device being used for their surgery is FDA-approved," he says, or that they make sure they are being treated with a laser that is under study in an FDA-sanctioned clinical trial.

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