Femtosecond laser facilitates corneal flap depth consistency

With the Pulsion FS laser, “bubbles” not blades, create the keratectomy.

ByRochelle Nataloni

NEW YORK — Patients who desire LASIK but fear the surgical cut now have an opportunity to experience the procedure’s benefits, thanks to flap creation with the Pulsion FS laser. This relatively new microkeratome-free form of LASIK relies completely on a femtosecond laser to perform the keratectomy.

“The Pulsion FS laser provides an excellent result for the correction of myopia, hyperopia and astigmatism. I think it will achieve center stage in the next 6 to 12 months as more surgeons gain experience,” said Lee T. Nordan, MD, at the Ninth Annual Ocular Surgery News Symposium here.

“Most patients think that LASIK is all laser. We have found that many patients become fearful once they learn that a blade is used in LASIK. With The Pulsion FS laser, it truly is all laser,” Dr. Nordan said.

Dr. Nordan reported that the Pulsion laser is still in prototype form. “A femtosecond is 10^-15 second. Because you have such a small spot size, it takes very little threshold energy to create the plasma field and the ablation. Essentially, we’re taking 3-µm ablation zones and stringing them together in a spiral pattern to create a keratectomy,” he said. The most important aspect of LASIK is consistent flap thickness, not ablation of the stroma. “If you have a flap that varies 10 µm from temporal to nasal, changing the stromal surface 0.25 µm is not the cause of optical problems. So the biggest issue is a good flap. With a good flap you usually get a very excellent result in LASIK,” he said.

How it’s done

---The Pulsion FS laser is manufactured by IntraLase.

Dr. Nordan avoids using dye to mark the cornea, relying simply on a 6-mm ring to mark the epithelial surface. He docks the eye to the laser using a suction ring that creates only 30 mm Hg of pressure on the eye, and then the cornea is applanated using a glass applanation plate. “Then the Pulsion laser creates hundreds of thousands, if not millions, of bubbles all in the same plane,” he explained. “This plane cannot vary by more than 4 or 5 µm because if the bubbles do not meet, there will not be a dissection. So one of the beauties of this new procedure is that if we can complete the procedure, we know we have a very sophisticated, consistent flap depth.”

Once the femtosecond ablation is made, Dr. Nordan continues with his standard LASIK routine. “I use a miotic pupil because I think it’s easier to keep things centered, and then I use a dry technique to replace the flap because I think it sticks faster and better that way. We can create any depth (160, 180 or 200 µm) and any size hinge we wish, located anywhere we want, and the result is a well-performed LASIK procedure,” he said.

Patient outcomes

At the time of this report, Dr. Nordan had performed 125 Pulsion flap procedures. Preoperatively, the first 70 consecutive eyes were a mean –3.5 D sphere, with 0.71 D cylinder. “One month postop they were essentially at spherical equivalent of zero. We’re doing well, and we’re using the same nomogram that I use for the regular LASIK procedure. There have been no complications, striae, recurrent erosions, infections or irregular astigmatism of any type, which I think speaks to the quality of the flap we are creating,” said Dr. Nordan.

One patient required a retreatment because a complete applanation was not achieved. “This is about the worst thing that can happen during a keratectomy, so we stopped. What’s very exciting about the Pulsion is that 45 minutes later we were able to proceed to retreat the patient just as though it were an original case,” said Dr. Nordan. The patient went on to have a normal LASIK, and did equally well as other patients.

“The femtosecond laser is very precise. We can create any diameter, flap depth and hinge design. But the most important issue is exact flap depth, consistently throughout the entire flap,” Dr. Nordan said. He thinks laser flap creation and LASIK will coexist in the marketplace because of the relative advantages of each procedure. He is currently charging $300 more for procedures with the Pulsion laser, though. “We think the technology justifies it,” he said.

For Your Information:

Lee T. Nordan, MD, can be reached at 9834 Genesee Ave., No. 209, LaJolla, CA 92037-1214; (858) 457-2220; fax: (858) 587-0528. Dr. Nordan has no direct financial interest in the products mentioned in this article, nor is he a paid consultant for any companies mentioned.

IntraLase Corporation, manufacturer of the Pulsion FS laser, can be reached at 3 Morgan, Irvine, CA 92618; (877) 393-2020; fax (949) 461-3323.