The study, led by a University of Illinois at Chicago researcher, is published in the December 2006 issue of the American Journal of Ophthalmology.

"Although there have been many studies of the safety and efficacy of both types of laser surgery, there has not been a large study directly comparing the outcomes of the two procedures," said Dr. Dimitri Azar, field chair of ophthalmologic research and professor and head of ophthalmology and visual sciences at UIC.

In the retrospective, case-matched study, eyes that had undergone laser eye surgery were matched for a number of measures, including visual acuity and astigmatism; 122 LASIK-treated eyes were matched for all measures with 122 LASEK-treated eyes from a review of the charts of 2,257 eye surgeries performed by Azar. All patients' outcomes included a follow-up of at least six months.

"We found that although there were some differences in the visual and refractive results that favor the LASEK procedure, the differences were not clinically significant," said Azar. "These results are in line with previous smaller studies that we reviewed comparing the procedures."

LASIK, which stands for laser in situ keratomileusis, was introduced in the mid-nineties and has largely replaced the older photorefractive keratectomy procedure, better known as PRK. Unlike PRK, where the surface layer of the cornea is scraped away to allow the reshaping of the underlying cornea, with LASIK a flap is made in the top cornea layer to permit access to the underlying cornea. LASIK avoids most of the problems of corneal haze, postoperative pain and slow rehabilitation seen in PRK, but complications are sometimes associated with the flap.