Excimer laser surgery has been improved and refined over the past 30 years, and the most mainstream procedure is now Lasik (excimer laser in situ keratomileusis). 3 The flap is reset and the procedure is completed. In the past, the flap was made by a microkeratome, but with the continuous development of excimer laser surgery, the femtosecond laser has gradually replaced the keratome and has become the mainstream of excimer laser surgery: femtosecond + Lasik. So what is the femtosecond laser? Femtosecond is a concept of time, 1 femtosecond is equal to 10-15 seconds or 1/1000 trillionth of a second. Femtosecond laser is an infrared laser that operates in pulses with a wavelength of 1053 nm and a very short duration of a few femtoseconds, the shortest pulse of laser light available to man. Since the duration is very short and the energy is released in an instant, it can focus a large amount of energy to a very small area of space to make microscopic cuts; and it does not produce thermal effects that can damage the surrounding corneal tissue. It is like an invisible scalpel that can create corneal flaps with precision. Compared with the mechanical knife femtosecond laser flap production has the following advantages: 1, to eliminate the medical source of infection: the use of laser production of corneal flap, the whole process without a blade, relatively eliminate the medical source of infection. 2, high accuracy: the production of corneal flap error value in ± 10-15um, the thickness of the same everywhere, while the use of microkeratome production of corneal flap generally exist in the peripheral part is slightly thicker, the central part of the thin situation, it is difficult to achieve the central and 3, high stability of corneal restoration: the flap is an embedded flap, which is more accurate. 4, low pressure on the eye: the negative pressure of the attraction ring used in femtosecond flap making is small (about 35 mmHg), while the negative pressure of corneal knife making is larger (about 65 mmHg). 5, wide range of people: for myopic patients with thin corneas and high myopia, it is more suitable for Femtosecond laser flap making. However, the femtosecond laser is expensive; compared with the corneal knife, the patient’s cooperation requirements are higher, and it is relatively difficult to lift the flap, which makes the surgery more difficult; for patients who have had other eye surgery in the past and then perform myopia surgery has certain limitations. Therefore, it is recommended that friends who want to do surgery choose the procedure under the guidance of the doctor, not the expensive one is good, but the best one for you!