Transition to femtosecond laser flap requires attention to detail

Accurate centration of suction ring, removal of bubbles and careful lifting of the flap are critical to optimizing patient outcomes.

David R. Hardten

Creating femtosecond laser flaps is a fairly safe and straightforward procedure with a moderate learning curve, according to one surgeon.

“I think that after you get through the initial transition, you’re then trying to master the nuances of a new technology,” OSN Cornea/External Disease Board Member David R. Hardten, MD, said. “With a little bit of education, you’ll do fine with femtosecond lasers, with minimal transition pain.”

Dr. Hardten described some of the challenges in making the transition from microkeratome-created flaps to femtosecond laser-created flaps at Hawaiian Eye 2009. He recalled his own transition to the technique about 4 years earlier.

“I was a pretty happy metal keratome user,” he said. “I was used to all the issues with it. I kind of knew how to prevent the biggest problems with metal keratomes.”

Keratome and femtosecond laser flap creation share some similarities, such as the importance of centering the suction ring and flap, and potential complications. However, surgeons must avoid a few pitfalls, Dr. Hardten said.

“You can still get complications,” he said. “It’s still a flap, so you have the potential for epithelial ingrowth or flap displacement, etc.”

Centration and docking

When applying suction, careful centration on the pupil and removal of excess fluid from the conjunctival surface to obtain good suction are critical, Dr. Hardten said.

“You don’t want to have a whole lot of extra fluid on the eye because you want to be able to see when the suction ring is in total contact with the conjunctiva,” he said. “You don’t want a false start for your suction ring application because it can create some indentation on the conjunctiva. And if that original place was not where you wanted it to be when you try to re-apply, it wants to go back to the same spot again. So, perfect centration first time around is helpful.”

Dr. Hardten said docking is made much easier when there is accurate centration of the suction ring.

“Docking is easy if that first step, that centration of the suction ring, is extremely well-centered,” he said. “I think that makes it much easier if it’s perfectly centered because then the applanation cone won’t be off-center.”

Dr. Hardten said he prefers a one-handed docking technique that allows the applanation cone to push down on the suction ring and eye, and then squeezes the clip to pull the suction ring into the applanation cone.

Monitor ring light to make sure all striae are resolved. Image: Hardten DR

“Then, if you need to, you can manipulate your centration on the screen, but I think you should have the goal that you’re well-centered on the pupil with your initial applanation,” he said.

Managing bubbles before lifting flap

Bubble formation is especially challenging, Dr. Hardten said. Bubbles can block the excimer laser tracker and impede iris registration. However, before lifting the flap, the surgeon has ample time to remove bubbles and avoid problems with tracking and iris registration.

“I like to put a little fluid on the cornea and massage those bubbles out of place before I lift the flap,” he said. “Also, test the tracker and the iris registration before you lift the flap because once you lift the flap, the clock starts ticking. Your cornea starts to dehydrate, and that could create a problem.”

Wavefront-based excimer laser treatments are especially beneficial with use of the femtosecond laser for flap creation, and in complex cases, such as enhancements, make certain that the topography confirms any irregular treatment suggested by the wavefront acquisition, he said.

Lifting and replacing the flap is similar to an enhancement and involves breaking the epithelium in the periphery in one spot first and separating the epithelium the entire way around before lifting the flap is helpful.

“You definitely don’t want to put excess tension on the hinge itself because you can potentially tear the hinge off. So I tend to separate the area by the hinge last. After the flap is up, make sure that the stromal bed is evenly dry before treating with the excimer laser,” he said.

“Replacing a femtosecond flap is similar to replacing a keratome flap. I like to make sure that the flap is in good position, the gutters are even for the entire 360°,” he said. “So dry the cornea off to look at the gutter, look at the central ring light to make sure there are no malpositioned striae.”

Overall, the femtosecond laser for flap creation has been a useful addition to the techniques for laser vision correction. The combination of wavefront-driven excimer laser ablation with femtosecond flap creation can create happy patients, he said. – by Matt Hasson

• David R. Hardten, MD, can be reached at Minnesota Eye Consultants, 710 E. 24th St., Suite 100, Minneapolis, MN 55404; 612-813-3600; fax: 612-813-3658; e-mail: drhardten@mneye.com.