|
|
|
|
|
|
| Return to Savvy Consumer Information Center - Home Page |
by Carol Lewis
For Jeri Goldstein everything was a blur. Without her contact lenses she couldn't distinguish people, the scenes on television, the stars at night, and, generally, the world at large. Then, in March 1998, the 49-year-old California resident had eye surgery, and all that changed.
"After wearing contact lenses for 35 years, you can't imagine the freedom I felt," says Goldstein.
Goldstein underwent refractive eye surgery, an elective procedure intended to correct common eye disorders, known as refractive errors, such as myopia (nearsightedness), hyperopia (farsightedness), and astigmatism (distorted vision). 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 it allows for an unparalleled degree of precision and predictability.
"Laser surgery is the most exciting advancement in ophthalmology," says James J. Salz, M.D., clinical professor of ophthalmology at the University of Southern California in Los Angeles and the doctor who performed Goldstein's surgery. But surprisingly, he says, despite its sudden popularity, "only 20 percent of ophthalmologists in the United States today are trained in its operation."
The Food and Drug Administration first approved the excimer laser in October 1995 for correcting mild to moderate nearsightedness. With that approval, the agency also restricted use of the laser to practitioners trained both in laser refractive surgery and in the calibration and operation of the laser. Currently, the excimer laser is only approved for use in a procedure called photorefractive keratectomy (PRK).
Precision Surgery
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.
Since 1995, two laser systems have been approved by FDA to treat mild to moderate nearsightedness and mild to moderate astigmatism with PRK: The SVX Apex excimer laser, manufactured by Summit Technology of Waltham, Mass., and the VISX excimer laser, manufactured by VISX Inc., of Santa Clara, Calif. FDA also has approved the VISX system to treat high myopia.
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.
What About LASIK?
A more complex procedure than PRK is laser in-situ keratomileusis, or LASIK. Performed for all degrees of nearsightedness, it is still in clinical trials and not yet approved by FDA. 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 such 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."
Advantages of LASIK
Some doctors believe that LASIK is a suitable procedure for correcting the most severe refractive errors. They also say that there is generally a faster recovery time after LASIK than after PRK. In addition, LASIK patients can see well enough to drive immediately and have good vision within a week.
After studying the options, Goldstein first decided on the LASIK procedure, but was surprised to learn that her doctor advised against it.
"Initially, I wanted the quick recovery that LASIK offers," Goldstein says, "but the bottom line was, which surgery will give me the best results, and after considering everything, eventually we agreed on PRK."
James Salz is currently involved in an FDA-sanctioned clinical trial at Cedars-Sinai Medical Center in Los Angeles, which is now studying the laser system specifically for farsightedness (hyperopia) with astigmatism. Although routinely performing laser eye surgery, he still encourages a small percentage of his low to moderately nearsighted patients to undergo radial keratotomy, or RK, an earlier refractive correction procedure that does not require the excimer laser.
With RK, incisions are made in a "radial" pattern along the outer portion of the cornea using a hand-held blade. These incisions are designed to help flatten the curvature of the cornea, thereby allowing light rays entering the eye to properly focus on the retina. The number and length of the incisions determines the degree of correction attained.
"Typically, this is still a practiced procedure for select people with very small corrections of myopia," Salz says.
Conversely, Crawford says that although he will mention RK as an option to his patients considering eye surgery, he is not in favor of this method. He says studies indicate that incisions made during this procedure, which penetrate approximately 90 percent of the cornea, appear to weaken the structure of the eye. Also, once you've had RK done you can't repeat it or have PRK done.
"I think that patients should understand and consider all available options for correcting refractive errors," Crawford says, "but I would never recommend RK to anyone."
Is Laser Surgery for You?
For some, like Goldstein, 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.
Looking Ahead
At present, a number of other lasers for eye surgery are currently 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. Currently, neither the Summit nor the VISX lasers have been approved for correcting farsightedness.
"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.
During the first few weeks immediately following laser surgery, Goldstein says, "Every week I kept thinking, 'this is as good as it gets'?" Then, she discovered by the sixth week, as predicted by her surgeon, that her eyesight was noticeably better and eventually stabilized.
"I would tell others to be patient about their expected outcome," she advises. "Even though with LASIK you can expect quicker results, I'm happy with the choice of PRK."
Carol Lewis is a staff writer for FDA Consumer.
You may be a good candidate for laser eye surgery if you:
--C.L.
--C.L.
In order to decide whether laser vision correction is a viable option for you, it is important to first understand how the eye works and why people need glasses or contact lenses to see well.
The eye works much like a camera; its primary function is to focus light. For the eye to see, light rays must be bent or "refracted" to meet at a single point through the cornea, the clear window at the front of the eye that provides most of the focusing power. Light then travels through the lens, where it is fine-tuned to focus properly on the retina, the nerve layer that lines the back of the eye and connects to the brain. The retina acts like the film in a camera, and clear vision is achieved only if light from an object is precisely focused onto it. If the light focuses either in front of or behind the retina, the image you see is blurred. A refractive error means that the shape of eye structures does not properly bend the light for focusing.
Having 20/20 vision means seeing at 20 feet what a normal person sees at 20 feet. However, if vision is measured at 20/40, it means a person has to walk up to 20 feet to see the same size letter that someone with 20/20 vision could see at 40 feet. And so on. People whose best-corrected visual acuity (what they see using glasses or contact lenses) is less than 20/200 in the better eye are considered legally blind, even though they still have enough vision to get around. Prior to laser surgery, Jeri Goldstein's visual acuity without her contact lenses was measured at 20/400 in her right eye and 20/200 in the left eye. Following surgery, her eyesight without contacts stands at 20/25 and 20/20, respectively.
--C.L.
The risks outlined below apply to both PRK and LASIK procedures. The chances of having a serious vision-threatening complication are minimal, and there have been no reported cases of blindness following either PRK or LASIK, says James Salz, M.D., clinical professor of ophthalmology. However, FDA is aware of a few instances of severe eye injury requiring corneal transplant.
Infection and delayed healing: There is about a 0.1 percent chance of the cornea becoming infected after PRK, and a somewhat smaller chance after LASIK. Generally, this means added discomfort and a delay in healing, with no long-term effects within a period of four years.
Undercorrection/Overcorrection: It is not possible to predict perfectly how your eye will respond to laser surgery. As a result, you may still need corrective lenses after the procedure to obtain good vision. In some cases, a second procedure can be done to improve the result.
Decrease in Best-Corrected Vision: After refractive surgery, some patients find that their best obtainable vision with corrective lenses is worse than it was before the surgery. This can occur as a result of irregular tissue removal or the development of corneal haze.
Excessive Corneal Haze: Corneal haze occurs as part of the normal healing process after PRK. In most cases, it has little or no effect on the final vision and can only be seen by an eye doctor with a microscope. However, there are some cases of excessive haze that interferes with vision. As with undercorrections, this can often be dealt with by means of an additional laser treatment. The risk of significant haze is much less with LASIK than with PRK.
Regression: In some patients the effect of refractive surgery is gradually lost over several months. This is like an undercorrection, and a re-treatment is often feasible.
Halo Effect: The halo effect is an optical effect that is noticed in dim light. As the pupil enlarges, a second faded image is produced by the untreated peripheral cornea. For some patients who have undergone PRK or LASIK, this effect can interfere with night driving.
Flap Damage or Loss (LASIK only): Instead of creating a hinged flap of tissue on the central cornea, the entire flap could come off. If this were to occur it could be replaced after the laser treatment. However, there is a risk that the flap could be damaged or lost.
Distorted Flap (LASIK only): Irregular healing of the corneal flap could create a distorted corneal shape, resulting in a decrease of best-corrected vision.
Incomplete Procedure: Equipment malfunction may require the procedure to be stopped before completion. This is a more significant factor in LASIK, with its higher degree of complexity, than in PRK.
Problems with a Perfect Procedure: Even when everything goes perfectly, there are effects that might cause some dissatisfaction. Older patients should be aware that they can't have both good distance vision and good near vision in the same eye without corrective lenses. Some myopic patients rely on their myopia (by taking off their glasses, or by wearing a weaker prescription) to allow them to read. Such a patient may need reading glasses after the myopia is surgically corrected. Another consideration is the delay between eye treatments. If one eye is being done at a time, then the eyes may not work well together during the time between treatments. If a contact lens is not tolerated on the unoperated eye, work and driving may be awkward or impossible until the second eye has been treated.
--C.L.
FDA Consumer magazine (July-August 1998)
| Return to Savvy Consumer Information Center - Home Page |
|
|
|
|
|
|
|
Get the Savvy Consumer Newsletter! (FREE)
|
|