To perform lasik surgery, ophthalmologists must cut a thin flap in the cornea (surface layer of the eye), lift the flap, remove some of the stroma (middle layer of the cornea) and replace the flap. Traditionally, the flaps have been created with a mechanical microkeratome — a small instrument that, once affixed to the eye, uses a sharp blade to cut a layer of the cornea. The femtosecond laser has become a popular and noninvasive alternative method for flap creation. However, not much is known about the difference in visual outcomes between the two methods.

Dr. Sanjay V. Patel from the Mayo Clinic College of Medicine in Rochester, Minn., and his colleagues measured corneal haze (backscattered light) and visual outcomes after lasik surgery, comparing results using the femtosecond laser for flap creation (bladeless) with those using the mechanical microkeratome.

The researchers enrolled 21 patients who had myopia or myopic astigmatism for treatment with lasik surgery. One eye of each patient was randomized to flap creation with the femtosecond laser, and the other eye’s flap was created with the mechanical microkeratome. They used a 15-kHz femtosecond laser from IntraLase Corp. of Irvine, Calif., to create a bladeless flap with a thickness of 120 μm. A mechanical microkeratome from Bausch & Lomb of Rochester, N.Y., was used to cut a flap in the opposite eye with a thickness of 180 μm.

The patients were examined before lasik and at one, three and six months after surgery for visual outcomes and corneal haze. After one month, the researchers discovered that the patients experienced about 6 percent more corneal haze in the eye assigned to the femtosecond laser than in the one assigned to the microkeratome. However, there was no difference after three and six months. Visual acuity, contrast sensitivity and other visual outcomes did not differ at all between the two treatments.

The researchers believe that their results indicate that either method of flap creation is acceptable for lasik surgery. However, they caution that not much is known about the differences in safety between the two methods. The team reported its results in the August issue of Ophthalmology.