Not Just for the Nearsighted Any More, LASIK Eye Surgery Advances

Photorefractive laser surgery seems to have moved "light years" ahead since it was first approved to treat mild to moderate nearsightedness in 1995. Now, the LASIK procedure is approved for use in farsightedness and astigmatism, too, and advances in technology and technique have made the treatment available to a much broader range of patients.

In the two-step LASIK procedure, surgeons correct refractive error with ever-improving precision by using an excimer laser. The laser works by removing microscopic amounts of tissue from the cornea. A thin flap is created, then lifted back to permit the more extensive laser reshaping of the underlying surface of the cornea.

"The LASIK procedure is designed to change the shape of the cornea," said Medical College of Wisconsin Professor of Ophthalmology Steven B. Koenig, MD, who practices at the Froedtert & The Medical College of Wisconsin Eye Institute. "The cornea is the clear membrane in the front of your eyes, the watch crystal or the window of your eye. And because the cornea does most of the focusing power of the eye, by changing the shape a little bit we can produce a large change in your prescription. In most cases, we can reduce or eliminate your need for glasses or contact lenses.

"What we do with LASIK is first create a 'split-thickness' flap in your cornea. Now, your cornea is about the thickness of a dime. The split-thickness corneal flap we make is about a third of the thickness of the cornea, so it's very, very thin. This flap is attached to the cornea by way of a hinge, so it allows us to fold it back and forth like the cover of a book.

"We first make the flap, fold the flap back, and expose the deeper layers of the cornea. Then we use an ultraviolet laser (the excimer), which uses cold ultraviolet light, to basically disrupt the atomic bonds within the corneal tissue. That disruption allows us to remove microscopic amounts of corneal tissue. We can do this in a pattern so that we can either flatten the cornea to treat nearsightedness, or steepen the cornea to treat farsightedness, or we can make the cornea more spherical to treat astigmatism."

An Evolution from PRK
Dr. Koenig is the only physician at Froedtert & The Medical College who performs LASIK surgery. He is fellowship trained, having spent two years just in the study of the cornea alone. He noted that LASIK is essentially an evolution from photorefractive keratectomy (PRK), which provides laser reshaping of the outer surface of the cornea only.

"The basic difference between PRK and LASIK is the use of a flap," said Dr. Koenig. "They both use the same laser and they can both treat nearsightedness, farsightedness and astigmatism. The only difference is the presence of a flap in LASIK that isn't created in PRK.

"PRK works very well and it's very safe and very effective. But it can be associated with a certain amount of discomfort postoperatively and the recovery of vision is relatively slow. LASIK is the most popular refractive procedure performed today. In fact, I believe it's the most commonly performed elective surgical procedure in the country.

"In LASIK the cornea is sculpted beneath a protective flap. The advantage to that is that the recovery of vision is very rapid, almost instantaneous. Almost everybody who has LASIK will be able to return to work the next day and be able to drive their car without glasses the next day. Because LASIK isn't associated with any sort of abrasion of the cornea, there is virtually no pain. It's effectively a painless procedure."

Today, only about 5% of laser surgery candidates at the Eye Institute are treated with PRK, said Dr. Koenig. LASIK is used for the rest with, as he put it, "no pain, rapid rehabilitation, and excellent results. It's a wonderful procedure."

Flap-Making and Software Improvements
LASIK has been made even safer and more effective in treating severe refractive conditions through a variety of hardware and software innovations. Among them are a new "IntraLase" laser system that can be used to create the corneal flap itself, and new "Custom Vue" computer software that uses state of the art light analysis to provide more accurate prescriptions.

"Now we can treat nearsightedness, patients with astigmatism, and we can treat farsightedness," said Dr. Koenig. "And we're able to treat higher degrees of each one of those refractive errors. It used to be only mild to moderate degrees of nearsightedness. Now we can treat higher degrees of nearsightedness, higher degrees of astigmatism and higher degrees of farsightedness.

The IntraLase laser is an optional technique for creating the flap that is coming into wider use. "Until recently we made the flap with a mechanical device called a microkeratome, which is basically an oscillating blade in an instrument that looks much like a miniaturized carpenter's plane," said Dr. Koenig. "That works very well, but we now have the ability to make that flap with an IntraLase laser.

"This device generates a near-infrared source of light that can be directed into the cornea. The result of that energy is that it creates microscopic bubbles of gas containing carbon dioxide and water. The bubbles will cleave the corneal tissue in a very precise plane, so we can generate thousands of these little bubbles at a specific location and that will basically make an incision in the cornea. We can do that horizontally or stack up those bubbles and make a vertical incision.

"That's important because it improves the precision of making the flap and reduces the risk of complications, which associated with this are minimal. IntraLase allows us to treat patients who otherwise might not be able to be treated with a microkeratome. Even for those who could be treated with a microkeratome, it increases the margin of safety. It takes a safe procedure and makes it even safer."

Elective Procedure 'Not for Everybody'
LASIK is an elective procedure that is not covered by most insurance plans. The basic fee for LASIK is about $1,950 per eye, not counting additional charges for evaluation and the IntraLase and Custom Vue options. For a variety of reasons, Dr. Koenig said, LASIK is not recommended for about one in five people who consider it.

"Some people aren't good candidates for LASIK," said Dr. Koenig. "The best candidates are people who fall within a certain range in terms of their nearsightedness and farsightedness and astigmatism. Occasionally people have preexisting eye problems that make them poor candidates. People who have no problems with their current contact lenses or glasses and are perfectly happy with what they have may not consider LASIK.

"So LASIK isn't for everybody, but it's something that people may consider if they're nearsighted, farsighted or have astigmatism and their glasses or contact lenses aren't working for them or they get in the way of their activities. They may be uncomfortable or have allergic reactions to their contacts, or (it's the) inconvenience of contact lenses or glasses.

"Most patients have refractive surgery because they're interested in participating in sports or physical activities where their glasses or contact lenses interfere, or if they can't wear their glasses or contact lenses and they want to improve their cosmetic appearance."

Minimal Risks and Complications
Complications from LASIK are generally minimal, said Dr. Koenig. "With any surgery there are risks, but LASIK happens to be one of the safest things that we do," he said. "Probably the most common problem is people not getting a full effect from the surgery, particularly people who are very, very nearsighted or farsighted. That's called an undercorrection.

"The beauty of LASIK is that we can usually go back after a few months, if you don't get a perfect result, and convert the same flap that we already made to touch it up. We can usually lift the flap and re-treat it and we usually get a great result." Undercorrections and overcorrections only occur in about 2% to 3% of LASIK patients, said Dr. Koenig.

"Occasionally, patients may have some dryness," said Dr. Koenig. "It usually resolves quickly and it's very rare for it to persist. An infection is very rare, maybe affecting one in 5,000 patients. Inflammation occurs in maybe one in 500 patients. A fraction of a percent of patients experience glare and halos in their vision. Those usually disappear, and rarely are they any worse than what patients experience with their contact lenses.

"LASIK isn't totally risk-free, but it's very safe. It's most important that you have a very careful examination, and that it be done by the same person who's doing the surgery, someone trained to evaluate your cornea and who has experience in refractive surgery. The evaluation shouldn't be left to another party. That's what distinguishes us from most other practices. LASIK, including IntraLase and Custom Vue, is the most exciting new development in refractive surgery. Imagine being legally blind one day and seeing 20/20 the next, without the need for corrective lenses. It's the dream of many, one we're finally able to realize."

Dan Ullrich
HealthLink Contributing Writer

Some information for this article was provided by the Froedtert & The Medical College of Wisconsin Eye Institute. Dr. Koenig presents monthly seminars on LASIK at the Eye Institute; call 414-456-5274 to register.

MCW Health News presents up-to-date information on patient care and medical research by the physicians of the Medical College of Wisconsin.