As people’s demand for quality of life gets higher and higher, more and more people want to cure their myopia through surgery, remove their pesky glasses or contact lenses, and restore their clear and bright vision once and for all. Therefore, in recent years, excimer laser myopia surgery has blossomed all over the country, and all kinds of advertisements are everywhere, boasting the excimer laser as a miracle, omnipotent, what “no incision, no rebound, no pain”, what “30 seconds to give you a clear world “It is a perfect surgery. In fact, we should look at excimer laser surgery with a scientific attitude, as any surgery has its advantages and disadvantages. Excimer laser surgery has certain risks, such as failure of flap making, laser eccentric cutting, post-operative infection and strong external impact can cause quite serious consequences, resulting in worse vision than before surgery or even blindness. These serious conditions aside, even a successful surgery cannot be considered perfect, because excimer laser surgery has another inherent and currently insurmountable biggest drawback – loss of visual quality. Visual quality is a concept at a higher level than visual acuity. It requires not only normal visual acuity of 1.0 or higher, but also clarity, comfort, and stability, involving factors such as aberration, contrast sensitivity, night vision, and tear film stability, in addition to the diopter being ortho-optic. Pragmatically speaking, the current excimer laser technology can only improve the naked eye vision, but not the visual quality; on the contrary, the visual quality is usually decreased after the surgery. I. Increased aberrations The eye is a masterpiece of nature. The eye is like a precision optical instrument composed of many lenses, each of which has its own aberration, but when these lenses are combined together, these aberrations cancel each other out and become small, resulting in clear, comfortable vision. Excimer laser surgery essentially changes the curvature of the cornea by removing part of the corneal tissue with a laser, thus changing the refractive power. While changing the curvature of the cornea, it also changes the aberration of the cornea, causing the aberration of the entire eye system to change. Theoretically, the postoperative aberration can be larger or smaller, but the current human understanding and application of aberration is far from making it more perfect than the natural state, which means that the postoperative aberration is increased in most cases and affects the quality of vision. The direct causes of increased aberration are at least: (1) the corneal flap cannot be returned to exactly the same position after the keratome cut, and the extremely small displacement is undetectable by the naked eye and current detection methods, but it can greatly affect the aberration, like a big wave on a calm lake. Even the aberration-guided cutting can only control the size of the aberration in the instant after surgery, and the current technology is still helpless in the aberration change during the corneal healing process. Contrast sensitivity is also an indicator of visual quality. Some myopic patients may feel that the color of the visual acuity chart has become lighter and less sharp than the original one, despite the fact that their visual acuity can reach 1.0 after surgery. Since the excimer laser only cuts the corneal tissue in the central 5-6 mm area during surgery, the light passing through this area is focused on the retina, while the peripheral corneas that are not cut are still in a myopic state, and when the light passes through the part of the cornea outside the treatment area, the blurred circle of myopia will be superimposed on the clear image made by the central treatment area, which only affects the quality of vision in mild cases and makes you feel a little blurry when you look at things, and in severe cases, it will cause symptoms such as glare and halos, which affect vision, and even dizziness and nausea. The decrease in contrast sensitivity is related to the degree of myopia and the optical cutting zone before treatment. The higher the original degree, the smaller the optical cutting zone, the greater the difference between the central and peripheral corneal curvature after treatment, and the more obvious the decrease in contrast sensitivity. Night vision loss Patients with over 300 degrees of myopia usually complain that their vision is not as good at night as it is during the day, or that they experience vision loss on rainy days after excimer laser surgery. In fact, this is a disadvantage of excimer laser surgery that has not yet been overcome, mainly due to the aforementioned decrease in contrast sensitivity and increased aberration. Under natural conditions, the size of the human pupil is 2.5 to 4 mm, which is smaller than the optical cutting zone, so the light from the peripheral cornea outside the treatment area rarely enters the pupil, while at night or under dim light conditions, the human pupil will physiologically dilate, even reaching more than 8 mm, far exceeding the diameter of the optical cutting zone, which will lead to obvious glare, especially when driving at night, when the opposite car drives high beam. The driver will feel a white blur in front of his eyes and cannot see anything. Therefore, we advise our friends who need to drive at night to be cautious when considering excimer laser surgery. The tear film is an important part of the refractive system of the human eye. An intact tear film makes the entire front surface of the eye very smooth and maintains stable vision. Once the tear film is destroyed and its integrity is lost, it will cause symptoms such as dryness, foreign body sensation and visual fatigue on the one hand, and the refractive system of the eye will be affected on the other hand, as light will scatter irregularly when passing through the tear film, which will also cause an increase in aberration and a decrease in visual quality. LASIK surgery cuts off the nerve endings in the superficial layer of the cornea when making the flap, resulting in decreased corneal sensitivity and corneal dystrophy, which affects the stability of the tear film and shortens the tear film rupture time, especially in patients who have a certain degree of dry eye before surgery, this feeling is more obvious after surgery, and even blurred vision. Of course, with the repair of corneal nerve endings, the stability of the tear film will be gradually restored, but this often takes six months or even longer, so patients who are ready to undergo excimer laser surgery must be fully prepared for this. In conclusion, excimer laser surgery is not as simple, safe and flawless as advertised. Although the rapid development of this technology has made it more mature, it does not mean that it is free of defects and complications. We should be careful in choosing the indications for surgery. With the development of technology, it is believed that one day excimer laser surgery will not only not cause the loss of visual quality, but also improve the original visual quality and realize the dream of 3.0 vision.