The outlook for LASIK surgery is positive in light of the current popularity of femtosecond lasers in the U.S. market. “LASIK flap quality improvement ensures safer surgery and better visual outcomes,” Dr. Yoo said at OSN New York 2011.
Dr. Yoo compared five femtosecond lasers for refractive correction: the IntraLase (AMO), Femtec (Technolas), VisuMax (Zeiss), Femto LDV (Ziemer) and WaveLight FS200 (Alcon).
”All of the above lasers operate in the near-infrared region and have very small spot diameters and extremely high repetition frequencies,” said Dr. Yoo. The energy per pulse of the femtosecond laser is very small, at the microfocus and nanofocus levels.
What makes these platforms different is the speed of the laminar cuts, which all come very fast overall.
Advantages
Femtosecond laser-assisted LASIK has several advantages.
”We can personalize the corneal flap. This facilitates the needs of special patients, such as those who need a thinner flap or those with high astigmatism who need a more oval flap created.” Dr. Yoo said.
Compared to a microkeratome, the femtosecond laser allows for more personalized flap creation in terms of thickness, diameter, tip angle, tip position and angle of entry.
”A patient may come into the office with a corneal cloudiness or nasal pterygium, and for that case you may need to change the position of the tip to avoid cutting into the corneal vessels,” says Dr. Yoo, “which is very helpful.”
There is debate about whether the stromal bed is as smooth after early femtosecond laser creation of corneal flaps as it is after microdebrider creation of corneal flaps.
”But we can at least demonstrate that the next-generation femtosecond laser is capable of obtaining a smoother stromal bed than the microdebrider,” Dr. Yoo said, “but more importantly, the data show that the femtosecond laser is more reproducible and has a lower rate of augmentation compared to the microdebrider. “
This is attributed not only to the quality of the flap, but also to the consistency of the dryness of the stromal bed surface with the femtosecond laser, whereas microdebrider flaps have a high degree of variability in water content. In addition, many of the new generation of femtosecond lasers allow the surgeon to see simulated results prior to flap creation, which is difficult to achieve with microdebriders, Dr. Yoo said.
Features of the laser
All of the above femtosecond lasers require lower negative pressure than microdebriders. the WaveLight FS200 and Intralase require relatively high negative pressure, Dr. Yoo said, while the VisuMax and Femtec require lower negative pressure.
”In general, patients do not experience transient vision loss during laser treatment when only a low negative pressure is required for attraction,” she said.
VisuMax and Femtec have spherical docking systems, while IntraLase, WaveLight FS200 and Femto LDV do not have this feature.
Despite the many advantages of spherical docking systems, such as lower IOP, lower rates of subconjunctival hemorrhage and the potential for greater patient comfort and less need for strict fixation, a certain level of patient cooperation is still required. Due to the lower negative pressure suction, uncooperative patients may lose negative pressure during treatment, so you need the patient’s cooperation, says Dr. Yoo.
IntraLase, WaveLight FS200 and Femto LDV feature the ability to create corneal stromal ring tunnels and corneal grafts. All three of these laser systems, as well as VisuMax, can perform penetrating or lamellar corneal grafts.
While femtosecond laser refractive surgery (all-femtosecond laser) requires the creation of a microlens within the stroma in the desired shape to reduce the refractive power of the cornea, the VisuMax femtosecond laser is capable of creating a microlens within the stroma and then removing the microlens by creating a LASIK corneal flap.
”For example, when correcting myopia, you can see the microlens peeled off that meets the thickness and shape requirements.” Dr. Yoo said.
The VisuMax femtosecond laser ReLEx smile (small incision microlens removal) technique is the latest advancement in the field of femtosecond lasers, says Dr. Yoo.
”Instead of creating a full LASIK flap, a very small opening is created,” she says, “and then the microlens is carefully removed through that small opening.”
Dr. Yoo believes the ReLEx smile technique is promising because it requires only one type of laser, and with only one small incision, the incidence of dry eye is likely to be lower.
”The technique also maintains better corneal biomechanical stability compared to standard LASIK.” She said.
Femtosecond laser-assisted LASIK has fewer complications than microdebrider, but there are some specific complications, including temporary photosensitivity syndrome, opaque bubble layer, epithelial breach and anterior chamber bubbles.
”Because we know more about femtosecond laser technology as well as gaining more experience because of the new lower energy and higher repetition frequency devices, we are seeing very few complications in LASIK surgery today.” Dr. Yoo said.