The Lasitome system (Gebauer Medizintechnik GmbH, Neuhausen, Germany), a new microkeratome available on the European market since February 2003 (Figure 1), shows considerable promise. Since its introduction to my clinic 3 months ago, I have been impressed by the device's efficacy and quality, and I have begun using it in almost all of my surgical cases. In more than 300 LASIK procedures I have performed with the Lasitome, I have not experienced any epithelial dislocation or free caps.
CAPABILITIES
The Lasitome's suction rings are highly effective, and the device creates excellent quality flaps. It makes a regular cut and leaves a smooth stromal bed surface. The microkeratome creates a customized nasal hinge that can range from 0.3 to 1.0 mm in length, depending on the patient's corneal topography and visual defect; in fact, in hyperopic patients, I can produce a small hinge and a large flap with a diameter that can range from 8.5 to 10.0 mm.
DESIGN
The Lasitome shares the same basic structure as the SKBM microkeratome (Alcon Laboratories, Inc., Fort Worth, TX), which is now retired from the market. The Lasitome, however, features two modifications. First, its applanation window is laterally secured to the head by two independent fixtures, micropins and setscrews, in order to more safely hold the window in the accurate position. Moreover, the applanation window provides a view of the entire cut of the cornea and corneal meniscus (Figure 2). Second, the suction rings have many holes along the side that adheres to the cornea. The holes are protected by diagonal bands and help the suction ring to attach itself more strongly to the cornea.
The microkeratome has two heads, one regular and one hyperopic, which can create various types of flaps. The standard-sized head cuts at 160 µm for applanations of up to 9.5 mm, and the larger head cuts at 130 µm for applanations exceeding 9.5 mm. The latter is useful in hyperopic cases in which the ablation zone of the excimer laser is usually wider in diameter. Both types of heads can also create thinner flaps (130 µm). The microkeratome's transverse speed may be set from 0.4 to 3.0 mm/second.
The Lasitome has two motors, one for oscillation and the other for advancement. As the head returns to the starting position after making the cut, the blade's motor stops. With only one motor functioning, the blade does not move. Therefore, the risk of damaging the flap is minimal during this reverse movement of the head.
CUSTOMIZATION
The technician can control the Lasitome's suction to the cornea and the cut the device makes directly from the console (Figure 3) or the foot pedal. Personally, I prefer that my technician manage everything manually from the console so that I may concentrate on the position of the ring and the cut.
For each case, I assist in determining the parameters of the cut. I prefer to create an appropriate meniscus beneath the window (including the flap's diameter and hinge and the speed of the pass across the cornea). The corneal meniscus diameter depends on the tipology of head used. Compared with that of other microkeratomes, the learning curve for this machine requires that more advanced surgeons operate the device, primarily because of its greater customizeability. After using the Lasitome, I appreciate the device's ability to customize the procedure for a variety of corneas, refractive errors, optical zone sizes, pupil diameters, and K values.
RARE COMPLICATIONS
Sometimes, especially in hyperopes, the cornea may become slightly decentered from under the ring during the suction phase. To prevent this occurrence, I suggest making a small nasal hinge close to the limbus and keeping the flap as large as possible. This technique protects the hinge area from the laser ablation.
In the rare instance that suction is lost, the blade and head of the microkeratome cease movement. Immediately returning the head to its starting position protects the incomplete flap and provides the opportunity to effectively manage the complication. Two months later, it will be possible to create a new flap with a different diameter and thickness.
I have not experienced any buttonholes with the Lasitome, and the risk of inducing a free cap is almost negligible with the device. I attribute this success rate to the ability to clearly view the pass of the blade through the meniscus once the head is properly engaged on the suction ring. Additionally, by following the two lines drawn on the applanation window, I can clearly view the border of the soon-to-be created flap.
THE BENEFITS OF A NASALLY HINGED FLAP
Because of the type of flap it creates, the Lasitome reduces the incidence of dry eye syndrome in post-LASIK patients.1 The device makes a lateral cut that, combined with the use of appropriate anesthetic drops, can help considerably reduce epithelial dislocation and dry eye syndrome after LASIK. Cutting temporally and creating a nasal hinge preserves the nasal innervation, which carries signals indicating dryness from the ocular surface to the brain.
CONCLUSIONS
Several new details differentiate the Lasitome microkeratome from the SKBM, including the secured applanation window, improved 19-mm rings with better holding force, an ergonomically improved handpiece design, and a new vacuum tubing system with luer-connection. I find the Lasitome microkeratome safe and able to maintain flap consistency. Future improvements for the LASIK procedure include a better quality of vision and the treatment of presbyopia and high astigmatism. The Lasitome's technology is certainly able to satisfy each patient's customized parameters.
1. Donnenfeld ED, Solomon K, Perry HD, et al. The effect of hinge position on corneal sensation and dry eye after LASIK. Ophthalmology. 2003;1105:1023-1029; discussion 1029-1030.
