A Closer Look by Elvira Maricic Laser vision correction can now give farsighted patients a close-up view print article      send to a friend

Far More Farsighted

A person with hyperopia, the medical term for farsightedness, can clearly see objects at a distance, but has trouble seeing up close. The condition occurs if the eyeball is too short or if the cornea is too flat, causing light entering the eye to focus incorrectly.

An independent research study known as "The Baltimore Eye Study" (conducted by investigators from Johns Hopkins University and supported by grants from the National Institutes of Health), revealed that the number of Americans over age 40 with hyperopia is nearly twice as large as those with myopia (nearsightedness).

"Up until they're about 40, everybody who has farsightedness can compensate for it by dialing in prescription power [focusing] on their own. After that, they start losing the power [to focus] and become more dependent upon glasses. They can no longer change their power automatically," says Robert L. Treft, MD, a board certified ophthalmologist at the Mountain View Eye Center in Layton, Utah.

Lasers to the Rescue

In October of 1995 the FDA approved the use of the excimer laser--a precise, computer-assisted laser--for the correction of moderate myopia. Three years later, approval was granted for the use of the laser in correcting hyperopia. 

Photorefractive keratectomy (PRK) was the first procedure to use the laser. In the procedure, which takes 30 to 60 seconds, the laser doesn't actually cut the tissue. Instead, it uses a beam of ultraviolet light to sculpt the surface of the cornea by vaporizing the tissue without damaging surrounding cells. After surgery, most patients achieve 20/40 vision.

While PRK is still around, most surgeons are currently using LASIK for the majority of their patients. LASIK, which stands for Laser Assisted In Situ Keratomileusis, also uses the excimer laser. In the procedure, which only takes a few minutes, an instrument called a microkeratome cuts a corneal flap, which acts as a hinge. The flap is folded back and the laser then reshapes the cornea below the flap. The flap is then closed, adhering naturally and requiring no stitches.

If the patient is nearsighted, tissue closer to the central part of the cornea is removed to decrease the curvature or flatten the cornea. If a patient is farsighted, tissue in the peripheral part of the cornea is removed to increase the curvature of the cornea.

In June, the FDA granted approval to the Sunrise Hyperion LTK (Laser Thermal Keroplasty) system, the first refractive laser procedure designed specifically for farsightedness. "They are allowed to treat low-levels of farsightedness," says Dr. Treft. "They use the laser to create burns in the cornea that shrink down the tissue, and can treat up to 2.50 diopters of farsightedness," he adds.

Differences of Opinion

As with any new procedure, the jury is still out on the LTK system. "I don't believe that it's as great a procedure as some people have talked bout, because the effects have been temporary. You have to overcorrect when you first treat [the patient] and there isn't a way to absolutely control the healing, so that the results are somewhat variable.

"Patients usually end up overcorrected for the first month or two, then they end up with fairly good correction, but we're not sure how long they'll be able to hold on to that because there haven't been any really long-term studies done with it," Dr. Treft adds.

Opinions also differ on the issue of PRK versus LASIK for vision correction. Although the long-term prognosis may be similar for patients undergoing laser vision correction, many surgeons like LASIK because it offers less discomfort after surgery, reduces recovery time, offers stable vision more quickly, and re-treatments, if necessary, are easier to perform.

Split the Difference

Undergoing laser surgery doesn't mean complete freedom from glasses or contacts for every patient. "It depends on what we hope to accomplish with the surgery," says Dr. Treft. "If you're simply going to correct their ability to see far away, those over 40 still may have difficulty seeing up close, in which case they would still have to put on a reading glass.  A lot of the patients are opting for something called Monovision, where one eye is focused far away and the other eye is focused at their desktop, in order to enable them to see without their glasses 90-plus percent of the time," he adds.

Complications rare, but possible

Laser vision correction, like any surgery, involves risk. While most problems and complications can be managed, they can occur in 1 to 2 percent of patients.  Complications may include:

. under and over correction
. astigmatism
. infection
. night vision difficulties
. delayed healing, and
. corneal haze

In addition, not everyone is a candidate for the surgery.  " If patients have irregular astigmatism or they had significant corneal scarring from before, this would not be a good procedure," says Dr. Treft.

The severity of hyperopia can vary, as the following chart demonstrates: