Femtosecond laser technology is fueling the development of new corneal surgery approaches. In refractive surgery, for instance, corneal flaps may now be created with higher reproducibility in flap thickness and flap edge design.

After forming the corneal cut by photodisruption, there is an incomplete separation of the stromal bed with the flap due to tissue bridges. The surgeon, therefore, is confronted with obtaining a new technique to open the flap.

A classic and safe technique to access the stromal bed is to create the flap by entering the corneal tissue near the hinge. The steel instrument, a Seibel-IntraLASIK Flap Lifter (Rhein Medical, Tampa, Florida), enters the side cut, and the flap is stretched against the counter resistance of the peripheral unseperated part of the flap. Those surgeons who have started on 5-, 10-, or 15-Hz femtosecond technology have chosen this technique because of its easy adaptability. One disadvantage, however, is that the steel instrument intrudes into a preformed corneal space, and there is a potential for via falsa penetration of the tissue with the steel instrument. Due to the varied initial interactions between the corneal tissue and the gas bubbles—formed by the femtosecond laser—effects of vertical or horizontal breakthrough may occur, forming an opaque bubble layer of softened and weakened tissue. In these cases, the surgeon may not be able to exit the side cut at the opposite side of the hinge. In a complicated case, intrusion of the instrument may also increase the (1) chance of tissue damage and (2) implantation of epithelial cells or detritus into the interface due to prolonged manipulation.

Flap opening difficulties may also arise when—as described above—the surgeon is unable to push the instrument fully to the other side of the hinge. In this case, the surgeon must widen the gap between stroma and flap from hinge to periphery several times in a multilane fashion. Thus, in otherwise uneventful treatments, microstriae are sometimes visible in the first postoperative week due to mechanical stress on the flap's inner side. Wavefront-guided treatments may suffer from mechanical stress because they are preferably performed on an untouched stromal bed with uniform dryness.

ALTERNATE APPROACH
I suggest an alternative femotosecond laser approach after flap creation to open the flap from the opposite side of the hinge. I call this approach flaporhexis. Below is a step-by-step guide to the alternative technique:
(1) Enter the side cut with the short hook side of the Seibel-IntraLASIK Flap lifter at the 9 o'clock or 3 o'clock position. Push down vertically into the gap (Figure 1).
(2) Turn the tip by 90º, and make a 180º swing to the contralateral side, following the tip inside the edge of the gutter (Figure 2).
(3) Use Baraquer forceps or the specially designed Flaporhexis forceps (Geuder, Heidelberg, Germany) to firmly grab the flap open at the 6 o'clock position (Figure 3).
(4) Lift the flap, with a strong and determined pull, back to the hinge (Figure 4).

At this point, the surgeon should find a virgin, uniform, dry stromal bed that is ready for wavefront-guided treatment. When the flap is refloated after the laser ablation, the slight mark of the forceps is stainable with fluorescein for some hours, but the flap is perfectly adapted in its gutter. In my experience, the uniform design of flaps created by this femtosecond laser technique transfers the optical higher-order aberrations found on the surface down to the ablation area of the corneal stroma.

USED WITH FEMTOSECOND LASERS
The surgical approach presented here is derived from what is commonly known as the can-opener technique, used when mechanical flap relifts are made for retreatments or enhancing procedures with the excimer laser. It was intended to reduce the mechanical trauma of separating the corneal tissue, taking advantage of the cornea's natural anatomy. We suggest that this flap creation method exclusively be used with the femtosecond laser since no preexisting cut but a virtual predetermined breaking point between the flap-to-be and stroma is made. The breaking point has yet to be separated by tearing.

We have completely converted our flap-lifting to this technique in February 2005. To date, we performed more than 700 consecutive flaps. Our standard average flap thickness is 100 µm (ie, the minimum flap thickness parameter suggested by Intralase [Irvine, California]). This measurement underlines the safety of this procedure as well as points out the biophysical sturdiness of the thin flaps created by femtosecond technology.

Like in any procedure, complications may arise. We have not, however, faced one complication that lead to BCVA loss due to flap malformation. One critical situation that may occur is if a pronounced line of tissue bridge occurrs due to eye movement. When tearing on the flap, the surgeon will feel a slight resistance that will be overcome by the momentum of the tearing. Very rarely does the surgeon face abandoning flap creation; it may be best if the resistance is too high.

We have experienced two incidents of tissue bite-out by the forceps, however, it may be easily repaired by inserting the flap particle after refloating the flap. These incidents have led to the design of the flaporhexis-forceps mentioned above. At any point during the procedure, the surgeon may switch back to their preferred technique of hinge opening. Therefore, it is an easy technique to learn, even for beginners.

In the earlier stages of femtosecond flap creation (eg, with the 5-, 10-, and 15-Hz technology), surgeons were taught—and many still use—the hinge opening technique. It is a safe access to flap creation, although mechanical tissue stress is evident when converting from mechanical microkeratomes to the femtosecond laser. Improved quality of tissue dissection, thanks to the 60-Hz femtosecond lasers, allows for our approach to be a safe and easy method for making the flap. We believe that this technique is appealing for any surgeon who does wavefront-guided treatments in combination with femtosecond laser technology.

Wolfgang Pfäffl, MD, PhD, is the medical director of AugenVersorgungsZentrum, in Weilheim, Germany. Dr. Pfäffl states that he has no financial interest in the products or companies mentioned. He may be reached at pfaeffl@msn.com.