EyeWorld India September 2017 Issue

55 EWAP DEVICES September 2017 by Michelle Stephenson EyeWorld Contributing Writer Femtosecond corneal laser platforms: Offering better vision and better flap predictability than microkeratomes continued on page 56 The first in this series highlights three femtosecond lasers available today F emtosecond 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 microker- atome is frequently the cause. Fem- tosecond 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 bet- ter 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 (Re- ichert Technologies, Depew, New York). Optical coherence tomogra- phy was used to measure central cornea thickness and corneal flap thickness. The ablation depth, residual corneal thickness, and postopera- tive corneal curvature were not significantly different between the femtosecond group and the micro- keratome group after surgery. The residual stromal bed thickness, cor- neal 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 biome- chanical 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 re- sidual stromal bed thickness, while CH decreased with the increase of pre-LASIK intraocular pressure and corneal flap thickness. There are a number of femto- second 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 crea- tion 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 accom- modates 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 technolo- gy,” said Karl Stonecipher, MD , Greensboro, North Carolina. “The laser works by photodisruption of corneal tissue in such a manner to improve the standard devia- tions 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 auto- matically centered on the pupil by the laser system, reducing dock- ing 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 appreci- ates 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 , Hou- ston, noted that the software al- lows surgeons to center the treat- ment, 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 deter- mined. 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 corne- al flap “locks” back into position, according to the company website. Traditional LASIK with a microkeratome-created flap is extremely safe; however, in cases with complications, the microkeratome is frequently the cause.