July 2017

 

REFRACTIVE

 

Device focus
Femtosecond corneal laser platforms: Offering better vision and better flap predictability than microkeratomes


by Michelle Stephenson EyeWorld Contributing Writer

   

The first in this series highlights three femtosecond lasers available today

Femtosecond lasers have revolutionized LASIK by providing better vision, more predictable flaps, and less increase in IOP.
Traditional LASIK with a microkeratome-created flap is extremely safe; however, in cases with complications, the microkeratome is frequently the cause. Femtosecond lasers offer a blade-free approach to corneal flap creation that is safer and more predictable.
A recent study compared the corneal biomechanical outcomes at 1 year after LASIK with flaps created by the Ziemer Femto LDV (Port, Switzerland) and the Moria M2 microkeratome (Doylestown, Pennsylvania) with a 110 head and a –20 blade and found that the femtosecond laser can provide better corneal flaps with more stable cornea biomechanics than a microkeratome.1
This prospective study included 100 eyes of 50 consecutive patients. The eyes were divided into two groups for corneal flap creation. Corneal biomechanical properties including cornea resistance factor (CRF) and cornea hysteresis (CH) were measured before and 1, 3, 6, and 12 months after surgery by Ocular Response Analyzer (Reichert Technologies, Depew, New York). Optical coherence tomography was used to measure central cornea thickness and corneal flap thickness.
The ablation depth, residual corneal thickness, and postoperative corneal curvature were not significantly different between the femtosecond group and the microkeratome group after surgery. The residual stromal bed thickness, corneal flap thickness, CH, and CRF at 12 months after surgery were significantly different between the Ziemer group and the Moria 110-20 group (P<0.01), with the Ziemer group having better corneal biomechanical results. The CRF and CH increased gradually from 1 to 12 months after surgery in the Ziemer group and increased from 1 to 6 months but decreased from 6 to 12 months in the Moria 110-20 group. At 1 year after LASIK, CRF and CH increased with the increasing of residual corneal thickness. Before LASIK, CRF also increased with residual stromal bed thickness, while CH decreased with the increase of pre-LASIK intraocular pressure and corneal flap thickness.
There are a number of femtosecond lasers on the market today. Here, EyeWorld highlights three of them, with more to be highlighted in upcoming months.

WaveLight FS200

The 200 KHz WaveLight FS200 femtosecond laser (Alcon, Fort Worth, Texas) offers fast flap creation times and delivers precise, predictable outcomes, according to the company website. Standard flap creation takes approximately 6.0 seconds. The platform provides automated vacuum control of the patient interface for consistent suction and minimized IOP and ocular distortion during suction.
Additionally, the laser offers adjustable hinge position and size, variable side-cut angles, flap sizes, and shapes. It combines a small focus with low pulse energy and a unique cutting pattern for accurate flap creation.
Using the proprietary Beam Control Check, the laser accommodates a wide range of patient variables for consistent flaps.
It has a high-quality microscope that provides visibility throughout the entire procedure. The adjustable joystick can accommodate either hand depending on the treated eye, and its motorized laser arm moves in three axes for more precise docking, according to the company website.
“The FS200 adds versatility to our latest femtosecond technology,” said Karl Stonecipher, MD, Greensboro, North Carolina. “The laser works by photodisruption of corneal tissue in such a manner to improve the standard deviations of flap thicknesses to ±5 µm. Routine accurate flap thicknesses between 100 µm and 110 µm are easily obtained because of the checks and balances of the system, such as the Beam Control Check of each individual patient interface or cone. The flap diameters are automatically centered on the pupil by the laser system, reducing docking time for the patient. Centered flaps with diameters chosen by the surgeon that don’t change in size with movement allow for accurate placement of the excimer laser photoablation each time with each patient.”
Dr. Stonecipher’s average time for a 9.0-mm flap is 9 seconds. “With smaller diameter flaps, I have seen that reduced to as low as 6 to 7 seconds. Having had LASIK myself back in 2002 when the time required to make a flap was more than a minute, the patient appreciates the reduced time under the laser, and he or she is less likely to have issues during the flap-making process,” he added.
Stephen Slade, MD, Houston, noted that the software allows surgeons to center the treatment, which is important. “It is able to do any type of cut: flaps, pockets, lamellar cuts, PKP, etc. It has a robust suction and rarely ever has a break in suction. It is fast and comfortable for the patient as well,” he said.

IntraLase

More than 5 million procedures have been performed safely and effectively using the IntraLase (Johnson & Johnson Vision, Santa Ana, California), according to the company website. This method allows surgeons to tailor the LASIK flap according to the shape of the patient’s eye. Everything from the diameter of the flap to the angle of its edges can be precisely determined.
The IntraLase method of flap creation can take 15 seconds or fewer per eye, depending on the parameters chosen by the surgeon. Including preparation time, the entire LASIK procedure typically takes about 10 minutes. Once the procedure is completed, the corneal flap “locks” back into position, according to the company website.
“In my hands, the IntraLase technology for LASIK has unique features that allow me to fully create a customized flap for a patient and has completely changed my approach to LASIK over the years,” said Stephen Coleman, MD, Albuquerque, New Mexico. “Flap diameter, flap shape, flap thickness, as well as the angle of the side-wall construction are all easily and readily programmable in my laser suite, for each individual patient. It is fast, precise, accurate, and reproducible.”
Dr. Coleman considers this technology to be the single greatest advancement in his 22 years of doing LASIK. “It is an absolute game-changer. It exceeds other huge steps forward, such as the introduction of eye-tracking systems as well as customized excimer treatments, both of which made LASIK a much better procedure. Modern LASIK, which in my estimation includes using a femtosecond laser to create the flap, is the approach I use when treating all my patients—family, professional athletes, movie stars, military pilots, and firefighters. It’s the best that I can offer in 2017,” Dr. Coleman said.

VisuMax femtosecond laser

The VisuMax (Carl Zeiss Meditec, Jena, Germany) employs high-performance femtosecond laser technology and is characterized by its cutting precision, speed, and gentle treatment technique, according to the company website.
With ReLEx SMILE, VisuMax begins a paradigm shift in refractive surgery: minimally invasive laser vision correction.
According to William Wiley, MD, Cleveland, the patient experience with this platform is the best in its class. “It has low pressure docking, which allows for comfortable procedures for patients and minimal eye irritation in the early postop period. It also allows for no loss of vision during suction, which is less anxiety-provoking for the patient. Patient fixation during lasering allows for easy docking, and low energy delivery allows for minimal inflammation and quick healing. Additionally, the precise depth provides confidence that appropriate corneal tissue is preserved,” he said.
Dr. Wiley uses the VisuMax for both flap making and SMILE. “It is key to have another modality to treat refractive errors, capturing more patients and offering more options for vision correction and providing unique advantages for certain patients,” he said.

Reference

1. Sun Q, et al. Effect of femtosecond and microkeratome flaps creation on the cornea biomechanics during laser in situ keratomileusis: one year follow-up. Int J Ophthalmol. 2016;9:1409–1414.

Editors’ note: Dr. Wiley has financial interests with Alcon and Carl Zeiss Meditec. Drs. Coleman, Slade, and Stonecipher have no financial interests related to their comments.

Contact information

Coleman
: stephen@colemanvision.com
Slade: sgs@visiontexas.com
Stonecipher: StoneNC@aol.com
Wiley: wiley@cle2020.com

Femtosecond corneal laser platforms: Offering better vision and better flap predictability than microkeratomes Femtosecond corneal laser platforms: Offering better vision and better flap predictability than microkeratomes
Ophthalmology News - EyeWorld Magazine
283 110
283 110
,
2017-06-30T14:14:27Z
True, 7