Unresolved issue of blade vs laser

Clinical benefit of femtosecond laser in flap creation remains unclear

Roibeard O’hEineachain

Posted: Saturday, June 1, 2019

Femtosecond lasers have a clear advantage over microkeratomes in terms of precision in LASIK flap creation, but whether that translates into a clinical benefit for the patient remains an unresolved question, as studies comparing the two technologies have yielded contradictory and inconclusive findings, said Mercè Morral MD, Institute of Ophthalmic Microsurgery, Barcelona, Spain.
“The theoretical advantages of using a femtosecond laser in LASIK procedures are that the laser may produce thinner, more accurate, reproducible and uniform flaps with a more planar architecture, and minimal thickness and edge variations.
“However, most studies comparing outcomes between femto-LASIK and microkeratome LASIK have been inconclusive, with similar visual outcomes and complication rates for both groups,” said Dr Morral, who presented the paper at the 23rd ESCRS Winter meeting on behalf of José L. Güell MD, who was unable to attend.
She noted, moreover, that microkeratomes have some theoretical advantages over femtosecond lasers. For example, histological analysis comparing the stromal surface quality after application of the two technologies suggests that the microkeratome provides a smoother cut than the laser and might be associated with a lower induction of total higher aberrations and spherical aberration.
However, that is still under debate, as the higher frequency of newer femtosecond lasers means they provide a much smoother cut than the older lasers.
She added that although IOP becomes more elevated during flap creation with a microkeratome, the procedure is much quicker, requiring only 20 seconds of suction. Creating LASIK flaps with a femtosecond laser takes longer and is associated with a higher rate of posterior vitreous detachment. In addition, the time between the cutting of the flap and the commencement of photo-ablation with the excimer laser is only 10-to-30 seconds with a microkeratome, compared to four-to-10 minutes with a femtosecond laser.
Dr Morral noted that femtosecond lasers appear to have an advantage over microkeratomes in terms of epithelial ingrowth owing to the vertical architecture of the edge of the flap. She reported that in Dr Güell’s opinion, the only situation where the microkeratome has a real practical surgical advantage is when you need to create a new flap in a cornea after a previous LASIK procedure. With the femtosecond laser it can be much more difficult to identify the interface of the newly cut laser-created flap from that of the flap in the previous surgery, which in turn may cause problems in lifting the flap.