Femtosecond flap complications occur at low overall incidence in study

March 1, 2010

Results of a retrospective study evaluating safety of LASIK flap creation using the 60-kHz femtosecond laser show complications occur at a low overall incidence and, ultimately, are visually insignificant, according to one researcher.

Lackland Air Force Base, TX-Results of a retrospective study evaluating the safety of LASIK flap creation using the 60-kHz femtosecond laser (IntraLase, Abbott Medical Optics [AMO]) show complications occur at a low overall incidence and, ultimately, are visually insignificant, according to Lt. Col. Charles D. Reilly, MD.

Overall, intraoperative complications occurred in six eyes (1.02%), and 33 eyes (7.16%) had a postoperative complication/abnormality, said Dr. Reilly, chairman, department of ophthalmology, Wilford Hall USAF Medical Center, Lackland Air Force Base, TX.

"Safety and visual acuity outcomes are paramount for any refractive surgery procedure performed in members of the U.S. Armed Forces, and when we began using the femtosecond laser for flap creation a few years ago, we believed it offered an added safety factor," said Dr. Reilly, also consultant to the USAF Surgeon General for refractive surgery.

"Documenting no loss from preoperative BSCVA is the best measure of safety for refractive surgery," he said.

"On that basis, the outcomes in this retrospective study are impressive and give me great confidence as a surgeon going forward in continuing to use the femtosecond laser for our patients," he added.

Identifying 'complications'

For the purposes of the study, Dr. Reilly and colleagues applied liberal criteria to identify flap "complications."

"If just one epithelial cell was seen at the border of the flap, it was categorized as a flap ingrowth," Dr. Reilly said. "Any slight microwrinkle was considered a microstria."

Among the 48 flap events, microstriae were most common (29 eyes, 4.9%), followed by epithelial ingrowth (nine eyes, 1.5%). Diffuse lamellar keratitis (DLK) occurred in four eyes (0.68%), and, during flap creation, a flap tear or incomplete side cut each occurred in three eyes (0.51%).

BSCVA outcomes were analyzed separately for each complication subgroup and showed consistently that BSCVA was excellent before surgery and remained so after. For eyes with microstriae, mean BSCVA was 20/17 preoperatively and 20/17.4 postoperatively, a difference that was not statistically significant. Eyes with DLK also had a slight worsening from the mean preop to postop BSCVA, 20/15.4 to 20/15.6, but again the change was not statistically significant.

"We included any case of DLK, no matter how mild, but no case in our series was severe enough to necessitate a flap lift or any other intervention besides increasing topical steroid use for a few days," Dr. Reilly said.

In eyes with a flap tear or incomplete side cut, mean BSCVA improved slightly after surgery. Among eyes with a flap tear, mean BSCVA was 20/19.8 preop and 20/18.9 postop; preop and postop BSCVA values within the incomplete side cut group were 20/17.8 and 20/16, respectively.

"What was even more remarkable in the eyes with an incomplete side cut was the fact that the mean uncorrected visual acuity at 1 month was 20/17.5, which bettered their best preoperative vision of 20/17.8," Dr. Reilly said.

For the control eyes having no flap complication, mean BSCVA was 20/16.1 preoperatively and 20/16.8 postoperatively. He said that although the study included almost 600 eyes, the sample size still is relatively small and outcomes were assessed only at 1 month after surgery.

"The early results are exceptional, and while we don't anticipate any changes in the safety profile over the long term, we will continue to follow these patients to confirm our early outcomes," Dr. Reilly said. He added that the femtosecond laser being used for refractive surgery has been upgraded from the 60-kHZ model to the 150-kHz device (IntraLase iFS, AMO).

"We are very interested in comparing our initial results using the newest generation of the femtosecond laser [with] our previous experience," he concluded. "Anecdotally, performance of the 150 kHz device has been much better in our hands."

FYI

Lt. Col. Charles D. Reilly, MD
E-mail: charles.reilly@lackland.af.mil

Dr. Reilly has no financial interest in the subject matter.