Dr Richard Duffey seeks to answer this question by comparing the results of femtosecond LASIK flaps with those of the mechanical microkeratome.
All refractive surgeons are interested in reducing flap complications and the risk of ectasia. Many continue to prefer LASIK over surface procedures for the increased comfort and faster visual recovery that patients experience when the ablation is performed under a lamellar flap.
In a way, perfecting the flap is the last frontier in making LASIK as safe as possible. So it's no surprise that people have been interested in the femtosecond laser and its touted ability to produce flaps of more consistent thickness than mechanical microkeratomes and their ability to do so with fewer complications and faster visual rehabilitation. "As a long-time user of the Moria LSK-One microkeratome, the studies I've seen comparing the femtosecond laser favourably to mechanical microkeratomes just didn't ring true to me," said Richard J. Duffey, MD of Mobile, Alabama, USA.
According to Dr Duffey, one of the problems is that most such studies compare standard-flap LASIK (130-180 μm) to thin-flap IntraLASIK (110 μm) (using the IntraLase femtosecond laser; IntraLase), which is really an apples-to-oranges comparison. Thin LASIK flaps tend to be of much more consistent thickness than the traditional, thicker flaps. "Personally, I noticed distinct improvements when I switched a few years ago from the LSK-One's 150 and 130 μm heads to the 100 μm head. I think if we really want to compare laser and mechanical microkeratome results, we have to keep the flap size similar," he added.
To add support to his argument, he compared the flap characteristics of 100 consecutive eyes of 50 LASIK patients, all made by him with the LSK-One 100 μm head, with those of 34 eyes with femtosecond laser flaps reported by Dr Perry Binder.1 In the laser flap group, the intended flap thickness was 110 μm.
The mean age of patients was 38 (range 21 to 59 years). They included 92 myopic eyes with a mean refractive error of -4.01 D (-1.37 to -12.62 D) and eight hyperopic eyes with a mean error of +2.69 D (+1.50 to + 3.12 D). Mean cylinder was 0.67 D (0 to 2.50 D). These patient demographics were very similar to those in Dr Binder's study.
"In mine and Dr Binder's studies, both mechanical and femtosecond flaps centred very well, with minimal variablility in flap diameter. There are a few differences, of course. The LSK-One makes a fixed nasal flap, with a variable hinge size. With the IntraLase laser, the hinge width is standard, but it can be placed in a variety of locations," confirmed Dr Duffey.
He continued, "In my series, there were no slipped flaps, no diffuse lamellar keratitis (DLK), no epithelial defects and two epithelial slides. Furthermore, day one postoperative visual acuity (VA) was 20/20 or better in 76% of eyes."