Patient Management
All-Laser LASIK
A surgeon talks about his experience using a femtosecond laser to create the corneal flap during LASIK.
By Lee T. Nordan, M.D., Carlsbad, Calif.

In my practice I encounter many patients who are concerned about the safety of LASIK. In particular, some of them express concern about the idea of a blade touching their eyes.

Since I've begun working with the IntraLase Pulsion femtosecond (FS) laser -- which can be used in place of a microkeratome to create the corneal flap -- I've been able to offer these patients a safe, all-laser alternative to the standard LASIK procedure. In fact, the FS laser has added a new level of safety to our LASIK procedures, minimizing complications while allowing us to maintain our excellent outcomes.

How it works

The laser's mechanism of action is simple and elegant: Infrared light energy from the Pulsion FS laser passes harmlessly through the outer layer of the cornea, vaporizing collagen fibers at the laser's focal point within the corneal stroma. The resulting gas forms microscopic vaporization bubbles about 3 microns in diameter within the tissue.

The femtosecond laser creates a dissection plane by generating an interconnecting spiral of microscopic bubbles within the stroma. The plane of bubbles gently separates the tissues. At the periphery, a "wall" of bubbles stacked from the plane to the surface creates a beveled edge, completing the flap.

Starting at the center and working outward, the computer-controlled laser creates a precise, tightly wound spiral pattern of cavitation bubbles within the stromal bed. The interconnected bubbles eventually form a dissection plane, gently separating the anterior surface layer of the cornea from the tissue below, without harming the adjacent tissue or the outer corneal surface.

During the final pass of the laser, as it reaches the outside edge of the intended flap, the beam creates a "wall" of bubbles by stacking them toward the surface (instead of extending the plane). This "wall" of bubbles cuts a precisely beveled edge from the plane to the surface, creating a hinged flap. (You can program the laser to make the bevel of the edge perpendicular or oblique.)

The surgeon can customize the operation for each patient by programming flap diameter and thickness and hinge location and width into the computer. The ability to change flap thickness for each patient is especially useful when dealing with highly myopic patients.

A safe procedure

The chief advantage of using this laser instead of a microkeratome to create the flap is a higher level of safety. Advantages include:

Consistency. The femtosecond laser cuts flaps reliably and reproducibly.

Short learning curve. Most surgeons can learn to use the laser quickly. Many of the skills required for using the femtosecond laser are familiar, such as centering the suction ring and locking the laser into the ring, which is similar to assembling a microkeratome on the eye.

Quick problem resolution. If a complication develops during flap creation, you can stop the procedure before cutting the outer perimeter; the dissection plane created under the corneal surface -- not yet a flap -- will disappear in about 30 minutes. The microscopic bubbles created by the laser are absorbed into the aqueous, and the corneal tissues return to their previous locations. After an hour you can safely begin the procedure again.

In contrast, a microkeratome-cut flap complication usually requires that the patient heal for several months before the surgery can be completed.

Minimal complications. I've used this laser in approximately 300 flap procedures with no significant complications to date. Also, because the Pulsion FS laser has FDA clearance for corneal resection, I've used it to safely perform about 15 lamellar corneal transplants.

In addition to the advantages during surgery, the FS laser has produced excellent outcomes:

• After 1 or 2 weeks, visual outcomes for patients whose flaps were created with the Pulsion laser have been equivalent to those whose flaps were created with a microkeratome. (However, patients with microkeratome-created flaps may achieve slightly clearer vision 1 or 2 days sooner than patients with laser-created flaps. This is because the cut made with the blade is a more continuous, smooth cut at the microscopic level than the cut made by the plane of bubbles.)
• After a year of follow-up, I've found no difference in visual outcomes between the two groups of patients.

Using the laser

As in a standard LASIK procedure, our patients receive Valium while in the waiting room. Staff members inform them that this procedure will be performed under anesthetic drops with no needles or blades involved.

I use pilocarpine to constrict the pupil because this makes it easier to center the suction ring and the excimer laser treatment. (Of course, pupil diameter in low light has been determined beforehand.) I cover the other eye and place a speculum in the operative eye.

The microscope on the excimer laser, which is located on my right, is ideal for positioning the suction ring on the eye. Once the ring is in position, I swing the patient under the Pulsion laser, on my left. (The femtosecond laser is freestanding and smaller than the excimer, so it fits conveniently in the surgical suite.)

The small end of the laser cone then locks into the suction ring. (Note: The current Pulsion model features an auto-seating suction ring, which saves times by guiding the cone into the ring.) The flat glass window at the end of the cone presses against the cornea, flattening the surface. On my command, the technician at the computer screen can center the Pulsion beam as necessary.

Creating the flap takes about 45 seconds. Then I remove the suction ring, swing the patient back under the excimer, lift the flap, and sculpt the stromal bed. To finish, I smooth the flap back down using a curved tier and a Weck-Cel sponge without irrigation. The beveled edges on the Pulsion-created flap make reseating it a simple task.

It takes me about 10 minutes to do both eyes, which is only slightly longer than it would take to perform LASIK on both eyes using a microkeratome.

A step in the right direction

The FS laser has many advantages, including safety, reliability, excellent outcomes, thinner flap capability, multiple uses and attractiveness to patients. Microkeratomes still have some strong selling points. (See "What About the Microkeratome?" above.) Nevertheless, I believe the FS laser will eventually become a fixture in every refractive surgery practice.

Dr. Nordan is assistant clinical professor of ophthalmology at Jules Stein Eye Institute at the University of California at Los Angeles. He also heads the Nordan Laser Eye Medical Group, in Carlsbad, Calif.