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Issue: March 15, 2000
March 15, 2000
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Laser microkeratome granted 510(k) status

The femtosecond laser is also being investigated as a stand-alone refractive surgery instrument.

Issue: March 15, 2000

IRVINE, Calif. — IntraLase received approval to market its photodisruptive laser microkeratome and plans to sell the device at the American Academy of Ophthalmology (AAO) meeting this year.

Researchers have not seen epithelial defects or ingrowth, buttonholes, partial flaps, diffuse lamellar keratitis or free flaps in the 40 patients treated with the laser keratome so far, Dr. Kurtz said.

The company has started research in Europe on using the IntraLase for refractive procedures, and they intend to start similar protocols in the U.S. this year.

Company president Randy Alexander said, “We are designing a surgical workstation. Our ultimate goal is a stand-alone laser to perform vision correction procedures.”

According to Eric Weinberg, vice president of sales and marketing at IntraLase, the company has not set a price for the IntraLase, an operating workstation complete with surgical microscope. The company will debut the device at the AAO’s annual meeting in Dallas this year.

Mr. Weinberg added, “Although this represents a true quantum leap in technology, we intend to make it affordable to refractive surgeons. We believe our laser technology will appeal to consumers and expand the market for laser vision correction.”

The Food and Drug Administration (FDA) granted the laser microkeratome a 510(k) premarket notification approval. The FDA grants this type of approval under section 510(k) of its regulations to premarket applications that demonstrate that devices are as safe and as effective, or substantially equivalent to, a legally marketed device that was or is currently on the market and that does not require premarket approval.

According to FDA documents, the agency clears most devices for commercial distribution by 510(k) approvals.

Step by step

Ron M. Kurtz, MD, vice president and medical director at IntraLase explained how the device works. Surgeons first place a suction ring on the limbus. They then lower an applanating contact glass onto the cornea through which the surgeon can verify and adjust centration.

The laser focuses femtosecond pulses at a predetermined depth.

Unlike excimer lasers, where the ultraviolet light is highly absorbed by the stroma, the infrared wavelength used in photodisruptive beams usually is not absorbed by the cornea, Dr. Kurtz said.

However, when the beams are concentrated to a small focal point, the short-duration pulses disrupt the chemical bonds of corneal tissue, generating a high-density plasma. This hot plasma expands rapidly, creating a shock wave and cavitation bubble of vaporized material.

The size of that cavitation bubble is related to the energy required to create plasma. For nanosecond pulses, this energy is relatively large and creates a large cavitation bubble. This requires a large space between pulses. Femtosecond pulses use considerably less energy and create 2 µm cavitation bubbles.

“When you couple this with a sophisticated computer control delivery system, one can deliver almost any surgical pattern within the cornea,” Dr. Kurtz said.

In its microkeratome application, the laser delivers those pulses in a spiral pattern to create a plane at the required depth, Dr. Kurtz said. The laser completes the flap by making an arc-shaped side cut from the plane to the corneal surface.

Surgeons can choose a hinge position and an angle for the flap, typically between 60° and 90°, Dr. Kurtz said.

Aligning the patient, placing the ring and applanating the cornea can be done in about 1 minute. The laser takes another minute to create the flap. Dr. Kurtz said he expects that time to drop even further as the software improves.

Safety considerations

The femtosecond laser is safer than a mechanical microkeratome, said IntraLase vice president for research and development Tibor Juhasz, PhD. Surgeons set the laser parameters relative to the base of the contact glass, so the results are completely reproducible, regardless of the eye’s shape or the suction generated by the ring.

The depth of the cut is accurate to within ±5 µm, as opposed to within ±30 µm with traditional microkeratomes.

Surgeons can vary flap parameters such as diameter with high precision, Dr. Juhasz said. If limbal vessels cause concern, surgeons can program the laser to create a smaller diameter flap.

Dr. Kurtz said that, unlike traditional microkeratomes, which require time to sterilize and assemble, the applanating contact glass is disposable and requires no assembly.

“There is a minimal learning curve, and the procedure is stress free for the surgeon, since it is done under direct visualization,” he said.

In some eyes, the flap did not re-cover the entire width across the stromal bed, but no epithelial ingrowth or other complications occurred as a result, Dr. Kurtz said.

The laser creates a much steeper side cut than the microkeratome blade, Dr. Kurtz said.

So far, researchers have used vertical side cuts to create the flap. With this incision, the flap fits into place similar to a manhole cover and has a high degree of lateral stability, he said.

“The cells would essentially need to go down a steep side cut and make a 90° turn to get underneath the flap, as opposed to a keratome, which has a more gradual entrance cut,” Dr. Kurtz said.

Also, the suction ring and applanating contact lens create about 35 mm Hg of intraocular pressure in the eye. Mechanical microkeratomes can create pressure above 80 mm Hg, sometimes to 100 mm Hg, Dr. Kurtz said.

Trials planned

The next likely application for the device will be for creating the channels and entry cuts for KeraVision’s (Fremont, Calif.) Intacs. Researchers have created intrastromal grooves in 15 eyes. According to Mr. Weinberg, creating grooves for Intacs takes about 30 seconds and the IntraLase accurately places the channel depth.

The laser could offer intrastromal ablation, as well as a new method: lenticular removal.

“You would not have to cut a full flap, you could cut a side port and pull lenticle out,” he said. “That would be a phenomenal procedure — all the benefits of LASIK without flap creation,” Mr. Weinberg said.

For Your Information:
  • Eric Weinberg, Tibor Juhasz, PhD, and Randy Alexander can be reached at IntraLase, 30 Hughes, Ste. 208, Irvine, CA 92618; (949) 461-3321; fax: (949) 461-3323; e-mail: info@intralase.com; Web site: www.intralase.com. Mr. Weinberg is vice president of sales and marketing at IntraLase. Mr. Juhasz is vice president for research and development at IntraLase. Mr. Alexander is president at IntraLase.
  • Ron M. Kurtz, MD, can be reached at 1000 Wall St., Ann Arbor, MI 48104; (734) 763-3727; fax: (734) 763-6098. Mr. Kurtz is vice president and medical director at IntraLase.