The Eyes Have It

You may have read about a pair of new procedures to help correct presbyopia--the difficulty focusing on close objects that typically begins around one's 45th birthday and eventually leads to reading glasses. News that the FDA might soon be approving the operation called conductive keratoplasty (CK), having approved laser thermal keratoplasty (LTK) last June, has focused attention once again on the rapidly growing--and increasingly confusing--field of corrective eye surgery.

With all the hype surrounding LASIK--the most popular laser treatment--and these newer procedures, it's hard for physicians to know what to advise patients who are tired of seeing the world through a couple of layers of glass. As promising as these operations may seem, there are some serious considerations that must be addressed before you put down your money (more than $2,000 an eye for LTK) and jump on the operating table.

Presbyopia (not to be confused with farsightedness) is caused by a gradual stiffening of the lens of the eye, which makes it more difficult to focus an image sharply on the retina. CK tries to improve focus by shrinking collagen fibers in the periphery of the cornea with short bursts of radio-frequency energy. The energy is delivered by a hair-thin probe to as many as 32 sites on each cornea. The contraction of the collagen has a purse-string effect that steepens the cornea's curvature. The procedure usually lasts less than a minute, but it can take several months for improvements to fully kick in.

LTK also works by heating and shrinking fibers in the peripheral cornea, but it has several advantages over CK. There are no probes, so nothing touches the cornea. Instead, laser energy is delivered directly to the surface of the eye. Only 16 spots are treated per eye, and they can be done all at once in less than three seconds. "LTK has the safest profile of any procedure thus far approved by the FDA," says Dr. Sandra Belmont of New York Weill Cornell Medical Center. "The concern I have with CK is its greater potential to produce astigmatism, because all of the spots are done individually, which constantly changes the shape of the cornea."

CK and LTK, like any other corrective eye surgery, will cause patients temporary discomfort. There may be a 24-to-48 hour period during which tears flow, and there is a scratching sensation akin to getting sand stuck in your cornea. Near vision returns immediately, but it takes a couple of days for the eyes to achieve their best focus. Distant vision may take a few weeks to recover.

LTK would be the first choice for many ophthalmologists because it is less invasive than LASIK and there are fewer potential side effects. But if you also have astigmatism or your hyperopia (farsightedness) is greater than 3.0 diopters, then LASIK is probably the procedure of choice.

Before making any rash decision, however, remember 1) these are elective surgeries and 2) you have only one pair of eyes. Generations before us have done quite well with bifocals. It wouldn't hurt to keep yours around a few more years until the kinks in the new procedures have been worked out.

Dr. Ian is a medical correspondent for NBC's Today show. E-mail: ianmedical@aol.com . See also the FDA's page on LASIK Eye Surgery .