Ultrastructural analysis demonstrates benefits of 150 kHz femtosecond laser

San Francisco-Results of a study using scanning electron microscopy (SEM) analysis to study the ultrastructural characteristics of lamellar flap specimens and stromal beds show marked differences depending on the instrument used for flap creation. The variation noted may have implications for clinical outcomes, said Renée D. Solomon, MD.

The study compared three femtosecond lasers, the 150 kHz iFS Advanced Femtosecond Laser (Abbott Medical Optics), the 60 kHz IntraLase (Abbott Medical Optics), Femto LDV (Ziemer), and a mechanical microkeratome, Zyoptix XP (Bausch & Lomb), that were used to create flaps in 16 human whole eye bank eyes. The globes used were not suitable for transplant and were from donors ranging in age from 58 to 77 years.

SEM analysis of the beds and edges of the keratectomy specimens was performed by an ophthalmic pathologist who was masked to the method of flap creation. The review showed irregularity in the stromal bed was more prominent and tissue remnants were more common when using the Femto LDV and the mechanical microkeratome for flap creation compared with the IntraLase and iFS femtosecond lasers. With use of the IntraLase, the stromal beds showed mild areas of surface irregularity, whereas surface irregularity was least when the iFS was used.

“Constructing the lamellar corneal flap is perhaps the most important part of a LASIK procedure,” Dr. Solomon said. “An irregular corneal flap creates an irregular refractive surface that may result in loss of BCVA, decreased contrast sensitivity, glare, and halos. However, even if the flap is regular and complete, it has been hypothesized that the smoother the surface, the better the final optical quality and visual outcome.”

“Further evaluation is needed to assess the impact of differences in stromal bed regularity on quality of vision issues as well as on strength of flap adherence,” she concluded.