New laser-surgery technique to perform cornea-transplant surgery

May 3 2005

A UC Irvine ophthalmologist and his team have invented a new laser-surgery technique to perform cornea-transplant surgery that can replace the use of traditional handheld surgical blades and potentially improve recovery time for patients.

The technique was developed by Dr. Roger F. Steinert, director of cornea, refractive and cataract surgery in UCI Health Sciences. Cornea transplants are performed on the “front window” of the eye, using living tissue from donors to replace corneas in which swelling, scars, distortions and degenerations are causing blindness. The work will be presented today at the Association for Research in Vision and Ophthalmology meeting, the largest eye research meeting in the world, in Fort Lauderdale, Fla.

The work will lead to human application of the high-tech procedure. Clinical trials are expected to begin by this summer at UCI.

While most transplants are successful in providing the patient with a clear cornea, the majority of cornea transplants take more than six months to provide good vision, and even then strong glasses or contact lenses are needed. In addition, stitches usually need to stay in place for years, because the cornea is slow to heal and, as a result, the transplant remains a weak spot, vulnerable to injury for the rest of the patient’s life. After the laser-based transplant, suture removal may be as soon as three months, and the strength of the repaired area may be nearly 10 times that of conventional transplants.

“By using the laser, a highly precise incision is created, resulting in a perfect match of the donor and the patient,” said Steinert, a professor of ophthalmology in the School of Medicine. “In addition to precision that exceeds anything that can be duplicated by even a highly skilled surgeon, the laser can create complex shapes that are impossible to achieve with conventional surgery.”

The study compared the results of conventional transplant surgical techniques to the results of the laser surgery. Utilizing 14 donated human corneas that were not medically suitable for transplantation, Steinert and his team performed simulated transplant surgery and then tested for the mechanical strength of the incisions and for induced distortion.

They found that the initial strength of the laser incision, even before any healing, measured almost seven times higher than that of the incision from the usual transplant technique performed by hand.

The laser used to cut the cornea is known as a femtosecond-pulsed laser, manufactured by Irvine-based IntraLase Corp. The laser fires 15,000 pulses per second, each pulse lasting only 400 quadrillionths of a second. (To understand how brief each laser pulse lasts, in one second a pulse of light would travel around the equator of the Earth seven times, but in one femtosecond a pulse of laser travels only the width of three human hairs.)

The location of the pulses in the cornea to create the incision is controlled by sophisticated optics and a computer, so that each pulse interconnects with the next, similar to the perforations in paper sheets that allow the paper to be torn cleanly.

As many as 40,000 cornea transplants are performed each year in the United States. The most common reasons for this procedure are swelling, clouding after damage from other eye diseases – a distortion known as keratoconus – and scarring after injuries or infections.

Co-workers on this project included Dr. Ronald Kurtz, associate professor of ophthalmology at UCI and co-inventor of the laser; Dr. Melvin Sarayba, project director at IntraLase, and Dr. Theresa Ignacio, a UCI research fellow. Steinert also is a professor of biomedical engineering and vice chair of clinical ophthalmology at UCI.

http://www.uci.edu