Femtosecond LASIK is an all-laser LASIK procedure that uses a femtosecond laser to make a corneal flap, which means that the flap is created with the femtosecond laser first, and then the excimer laser is used to make the corneal stromal cut. It is a very popular form of myopia surgery at the moment. What is a femtosecond laser? Femtosecond laser is a laser that operates in pulses of very short duration, only a few femtoseconds, a femtosecond is 10-15 seconds, or one trillionth of a second. Femtosecond laser has several characteristics: First, it is thousands of times shorter than the shortest pulses obtained by using electronics, and is the shortest pulse available to man under experimental conditions. The second characteristic of the femtosecond laser is its very high instantaneous power, which can reach one million billion watts, a hundred times more than the total power generated worldwide. The third characteristic of the femtosecond laser is that it can focus to a region of space smaller than the diameter of a hair, making the electromagnetic field several times stronger than the force of an atomic nucleus on its surrounding electrons. In the medical field, the femtosecond laser can be used as an ultra-precise surgical scalpel and is now successfully used in the field of ophthalmology for the creation of corneal lamellar flaps in excimer laser treatment of myopia, as well as other corneal procedures. The main difference between femtosecond laser surgery and conventional excimer laser surgery with a mechanical corneal lamellar knife is that the flap is made differently: femtosecond laser surgery uses a laser to make the flap without a blade, while conventional excimer laser surgery uses a mechanical corneal lamellar knife to make the flap, and the excimer laser cutting is the same after the flap is made. The negative pressure of the suction ring used to create the flap with the femtosecond laser (approximately 35 mmHg) is significantly lower than the negative pressure of the mechanical corneal lamellar knife (approximately 65 mmHg). Therefore, the use of femtosecond laser to create the corneal flap can greatly improve the safety of excimer laser surgery for myopia, especially for patients with thin corneas, large corneal curvature variation, and high myopia is a great blessing. The advantages of the femtosecond laser: 1. The femtosecond laser is used to create the corneal flap in LASIK myopia surgery, and its greatest advantage is that it produces a very high accuracy corneal flap thickness, and its accuracy (fluctuating at 10-15um) is three times greater than the accuracy of the laminar knife (fluctuating at 30-45um). “Femtosecond laser” is more than 100 times more accurate than laminar knife, which is unparalleled by laminar knife, and is safer for any patient. 2, reduce the risk of surgery In traditional laminate knife surgery, if the blade rotates during the process of negative pressure ring loosening and other accidents, the production of corneal flap will completely fail, the surgery can only wait for three months to do again, bringing great psychological pressure to patients and doctors. In the case of a similar accident with the femtosecond laser, the surgeon can simply put the negative pressure ring back on and immediately replenish the laser without interrupting the surgery. Because the femtosecond laser only produces some water and bubbles to push away the corneal tissue when creating the flap, there is no damage to the tissue, and multiple surgeries can be performed on the same affected area, greatly improving safety. It is also worth noting that the negative pressure of the suction ring used to create the flap with the femtosecond laser (about 35 mmHg) is significantly lower than the negative pressure of the mechanical corneal lamellar knife (about 65 mmHg). The lowest negative pressure in femtosecond laser is Ziemer LDV femtosecond laser. 3, more accurate reset The lamellar knife is horizontal cutting, and the surface of the eye is a sphere, so the flap profile is “cup and lid” type, and the adhesion with the eye matrix is not good enough; while the corneal flap made by femtosecond laser and the eye matrix is “underground well lid” type. The flap is embedded in the eye, so it is easy to reset and bite tightly without misalignment, and there are no complications such as flap fragmentation or button flap. The laser light source also avoids the residual metal debris that may be caused by the use of lamellar knife. 4, post-operative visual quality more perfect “femtosecond laser” can accurately open the eye tissue molecular chain, making a more uniform and perfect corneal flap, effectively avoiding the laminate knife flap may appear medical aberration, avoiding foggy days, rainy days and driving at night and other visual conditions such as glare, blur, so that myopic people The quality of vision tends to be perfect. 5, not affected by corneal curvature In the past, the corneal thickness was affected by nearly 10% of patients who were too deep and too thin to undergo traditional laser surgery such as LASIK. Femtosecond laser surgery can perfectly cut a thinner corneal flap, thus increasing the correction range of myopia laser surgery, while not affected by corneal curvature, so it is a great blessing for myopic patients with thin corneas and large corneal curvature variation.