The University Record, July 16, 1997

New U-developed laser performs high-precision corneal surgery

This scanning electron microscope image shows the internal surface of a human cornea following an incision made with the U-M laser to create a flap in the exterior surface of the cornea (large circle at left). A small, thin section of tissue called a lenticule (shown at right) was cut out and removed from the middle layers of the cornea. After the procedure, the exterior flap is repositioned. Removing the lenticule corrects nearsightedness by flattening the surface of the cornea. Magnification: 10x. Photo courtesy Tibor Juhasz

By Sally Pobojewski
News and Information Services

University researchers have developed and demonstrated a new, high-precision laser for eye surgery that can be used to perform surgical procedures within the transparent cornea of the eye-something not possible with current laser technology.

The U-M laser uses powerful light pulses lasting just a few hundred femtoseconds, or quadrillionths of a second. According to Ron M. Kurtz, assistant professor of ophthalmology, these ultrashort pulses require less energy to cut tissue and do not create large "shock waves" that can damage surrounding structures.

Kurtz is testing the laser for use in corneal refractive surgery for vision correction and in corneal transplantation. Future research will test the laser's effectiveness in the treatment of glaucoma and cataracts.

The new laser system was developed by a team of scientists from the College of Engineering's Center for Ultrafast Optical Science and the Medical School's W.K. Kellogg Eye Center.

Tibor Juhasz, an associate research scientist with joint appointments in the College of Engineering and the Medical School, presented the results of recent experiments with the U-M laser at the Advanced Opthalmic Laser Surgery Conference held June 25-28 in Interlaken, Switzerland. These studies compared the precision cuts made in human cadaver corneas with the U-M laser with cuts made by laser and mechanical surgical devices currently used by opthalmic surgeons.

"Cuts made by the U-M's femtosecond laser had extremely high surface quality with accuracy better than 10 microns," Juhasz says. "These results were markedly better than similar cuts made with mechanical devices, which are associated with significant risks and complications. Other lasers were unable to perform the procedure."

"Although the new laser will not be available for general patient use for at least three to four years, it could represent a major advance in the surgical treatment of several eye diseases and conditions by avoiding the risks and complications associated with less precise mechanical and laser techniques," Kurtz says.

An analysis of the optimal laser parameters for corneal surgery based on work by Kurtz and several U-M colleagues is being published in an upcoming issue of the Journal of Refractive Surgery. Animal tests are under way, with plans for human testing in the near future.

A prototype of the new surgical laser system was designed and built by Juhasz and his colleagues in the Femtosecond Medical Research Laboratory at the College of Engineering's Center for Ultrafast Optical Science (CUOS). Since it was established in 1990 with $14.3 million in funding from the National Science Foundation and the state of Michigan, CUOS scientists have developed ultrashort-pulsed laser technology for many applications in high-speed communications, manufacturing and biological imaging. CUOS lasers are based on a technique called chirped pulse amplification, developed by Gerard A. Mourou, professor of electrical engineering and computer science and director of the research center.

The U-M has applied for several patents related to ultrafast lasers and is currently assisting in the establishment of a new company to commercialize the technology. A corporate partner will provide the delivery system technology and additional intellectual property for the new company, called InterLase, which will be established in Ann Arbor this summer.

Research leading to the development of the new laser was funded by the National Science Foundation, the Office of the Vice President for Research, the College of Engineering, the W.K. Kellogg Eye Center, the Research to Prevent Blindness Foundation, and the Midwest Eye Bank and Transplantation Centers.

Tibor Juhasz with equipment used for the high-precision laser. Photo by Bob Kalmbach