Laser Eye Surgery

Femtosecond lasers can make clean, high-precision cuts in the human cornea.

A joint team of physicists and ophthalmologists at the University of Michigan has developed a new bladeless laser surgical method, which may help reduce complications and improve overall results of the popular Lasik eye surgery.

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According to a recent study of 208 procedures in 108 patients, femtosecond lasers can make clean, high-precision cuts in the human cornea that offer superior reliability and fewer complications than cuts made with mechanical devices now used in most LASIK procedures.

Intralase Corporation, a university spin-off, commercialized the technology and currently has over 40 lasers operating in clinics around the country. Over 30,000 procedures have been safely completed with the new technology.

LASIK, or laser in situ keratomilieusis, surgery reduces refractive error in the eye by reshaping or removing a portion of the cornea with an excimer laser. But before an excimer laser can be used, a thin flap in the cornea must be cut and folded away from the eye to provide better access to the tissue to be sculpted.

Creation of this flap is one of the most important steps toward insuring a successful and trouble-free procedure. In the traditional LASIK procedure, a microkeratome is used to create the flap.

The microkeratome relies on a mounted metal razor blade to cut the flap in the cornea. Even in very skilled hands, accurate depth and consistent flap thickness can be difficult to control with the device.

Flap-related complications occur in as many as 5 per cent of microkeratome LASIK cases, often delaying recovery of visual acuity or occasionally leading to permanent visual loss.

The new procedure replaces the microkeratome with a femtosecond laser, making the procedure completely bladeless and reducing the overall complexity of the surgery. Femtosecond lasers, which emit pulses of light that are a billion times shorter than an electronic camera flash, create a string of 3-micron bubbles just below the surface of the cornea.

These bubbles then create a precise and well-defined flap through a process known as photodisruption. The process leaves a more well- defined flap, while doing less damage to surrounding tissue than a microkeratome.