The University Record, May 7, 1996

U-M researchers develop laser systems for delicate surgery

Ron M. Kurtz, assistant professor of ophthalmology, examines a patient at the W.K. Kellogg Eye Center. Researchers at the Center for Ultrafast Optical Science (CUOS) are working with Kurtz to develop new 'ultrashort pulse lasers' for use in eye surgery and other medical applications.

Photo by Bob Kalmbach

By Sally Pobojewski
News and Information Services

Researchers at the Center for Ultrafast Optical Science and the W.K. Kellogg Eye Center are working together to develop new laser systems to perform precise procedures, such as intraocular microsurgery, on delicate eye tissue. Once perfected, the new lasers could avoid many of the complications of current surgical and laser treatments.

"Lasers now used inside the eye include so-called 'continuous wave lasers,' which use light to burn tissue, and 'pulsed lasers,' which tear tissues with mini-explosions," says Ron M. Kurtz, assistant professor of ophthalmology.

"Although useful in treatment of several eye diseases, current commercial lasers are not capable of removing tissue without producing significant inflammation and scarring."

The U-M device will use powerful laser light packaged in pulses that last for just a few quadrillionths of a second. Called ultrashort laser pulses, they can ablate or vaporize tissue without creating large "shock waves" that can damage surrounding healthy tissue.

"Ultrashort pulsed lasers produce very localized ablations, which should be especially useful in eye surgery where delicate structures can be easily damaged," Kurtz says. "Another important feature is the ability to focus the laser light through the clear cornea onto structures within the eye without the need for a surgical incision."

"The University can be extremely proud of this groundbreaking and promising collaboration to research and develop ultrafast lasers for use in eye surgery," says Homer A. Neal, vice president for research. "The faculty of the Center for Ultrafast Optical Science and the W.K. Kellogg Eye Center are to be commended for bringing this innovative project to this important stage. It is particularly exciting to see an initiative which unites so many of the exemplary research strengths of the University ranging from the fundamental to the highly applied."

A prototype of the new surgical laser will be designed and built by Tibor Juhasz, associate research scientist, and Xinbing Liu, assistant research scientist, in the new Femtosecond Medical Research Laboratory at the College of Engineering's Center for Ultrafast Optical Science (CUOS). Biological responses to the laser will be evaluated at the W.K. Kellogg Eye Center by Kurtz and Victor M. Elner, associate professor of opthalmology.

Since CUOS was established in 1990 with $14.3 million in funding from the National Science Foundation and the state of Michigan, research scientists at the center have developed ultrashort pulse laser technology for many applications in high-speed communications, manufacturing and biological imaging. 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, CUOS lasers produce extremely short, powerful optical pulses in the range of femtoseconds, or quadrillionths of a second.

"The shorter the laser pulse, the more confined the surgical effect," Juhasz explains. "With optical pulses in the femtosecond range, we hope to be able to produce a laser incision as fine as half the width of a human hair."

Even though the new laser system will be more complex than anything currently available, Liu says it also must be compact, reliable and inexpensive, since it eventually will be used by surgeons in an office setting.

Once the prototype is built, the Kellogg group will begin testing the new laser in several potential surgical applications, including glaucoma. Affecting 1.5 million Americans, glaucoma is associated with increased pressure inside the eye that damages the optic nerve. To lower the pressure, surgeons currently use a variety of drugs, laser and surgical treatments---none of which are totally successful or without side-effects, according to Paul R. Lichter, the F. Bruce Fralick Professor of Ophthalmology and co-investigator on the research project.

"It is exciting to contemplate that utilizing this new technology, it may be possible to create permanent drainage channels to reduce elevated intraocular pressure," Lichter says. "If this application is found to be effective, it will have major advantages over other incisional and laser surgical procedures now being utilized. The lack of collateral tissue damage is a marvelous patient benefit in reducing scarring that can lead to failure of glaucoma surgical procedures."

The group also plans to evaluate the laser in other ocular conditions including cataract and vision correction. Other Medical Center researchers will use the femtosecond laser to explore the interactions between laser pulses and biological materials. This long-range research may eventually lead to additional medical applications in neurology, dentistry, vascular surgery or dermatology, according to Juhasz.

The U-M has applied for several patents related to ultrafast lasers and is exploring commercialization and licensing options for the new technology. Funds for equipment and initial operating expenses for the Femtosecond Medical Re search Laboratory were provided by the Office of the Vice-President for Research. Support for faculty and staff re searchers is being provided by the W.K. Kellogg Eye Center and the Center for Ultrafast Optical Science.