Wednesday, May 03, 2006

Results with Newer Bladeless LASIK Equivalent to Standard Microkeratome LASIK

LASIK SURGERY Ultrasound probe measures the thickness of the cornea in preparation for LASIK surgery at the Hohenzollern Clinic for Refractive Surgery. LASIK stands for laser in situ keratotomy and is surgery that corrects near-sightedness by reshaping the cornea with a laser

LASIK (Laser-assisted in situ keratomileusis) involves treating nearsightedness, farsightedness or astigmatism by reshaping the eye's cornea to alter the way the eye refracts light. LASIK involves creating a flap, removing a defined amount of corneal tissue by an excimer laser, and replacing the flap. In standard LASIK with a mechanical microkeratome, the flap is created by a blade; in bladeless LASIK, the newer type, the flap is created by a femtosecond laser.

"At six months after surgery, there are no differences between the eyes that had bladeless or microkeratome LASIK with respect to visual acuity (vision as measured by reading an eye chart), contrast sensitivity (ability to discriminate bright objects from dark objects), or in perception of stray light or glare, such as the glare from oncoming headlights," says Sanjay Patel, M.D., Mayo Clinic ophthalmologist and study investigator.

Given the equivalent findings thus far in eye health and vision between the two types of LASIK, Dr. Patel slightly prefers bladeless LASIK due to its potential safety, which was not measured in his study. "I'd say the short-term outcomes are equal and the risks are, in theory, less with the bladeless technique, although our study was not designed to compare risks," he says. "Bladeless LASIK is potentially safer because of its computer-controlled precision, the ability to visualize the flap being created, and to stop the procedure whenever necessary. That said, however, the risk of complications with a traditional, microkeratome blade is very small: some vision loss from surgery with a microkeratome blade occurs in well under 1 percent of all cases. The long-term risks of either procedure, however, are unknown, and defining them is the primary purpose of our study."

The study followed 20 patients who received LASIK for nearsightedness or astigmatism. Each patient was treated with microkeratome LASIK in one eye and bladeless LASIK in the other eye. The researchers found no difference in subbasal nerve density between types of surgery, though the density decreased after both treatments compared to density before LASIK. Corneal sensitivity did not differ between microkeratome and bladeless LASIK. Subbasal nerve density and corneal sensitivity do not impact vision, but rather the potential to heal from a scratch or other injury to the eye. High-contrast visual acuity, the capability to see fine details, and contrast sensitivity, the ability to perceive contrast in objects and their environments, also did not differ between LASIK types. The researchers found corneal backscatter was greater with bladeless LASIK for the first three months after surgery, yet the patients perceived no difference in vision after three months between their eyes treated with bladeless or microkeratome LASIK. Backscatter is haziness in the cornea that is usually invisible to the naked eye and is identified through testing in a physician's office. Cell densities in all layers of the cornea also did not differ between the LASIK surgeries.

The ultimate goal of the Mayo Clinic study of microkeratome versus bladeless LASIK is to obtain long-term information about patients' vision and eye health five years following surgery. The results presented now represent the first six months of findings.

Other Mayo Clinic researchers involved in this study include: Cherie Nau; Jay McLaren, Ph.D.; Jay C. Erie, M.D.; Leo Maguire, M.D.; and William Bourne, M.D. None of the investigators has any commercial interests. The study was funded by the National Institutes of Health, Research to Prevent Blindness, and Mayo Clinic.

Source / Credit: Mayo Clinic