I. What is a distance lens? A distance lens is a medical device that can regulate myopia and control the deepening of vision, and is by far the most scientifically based. Through optics and other related disciplines, the lens allows the eye to look far away through special optics, which means that when you use the lens, your eye is actually relaxed when you keep looking near. Therefore, it also achieves the effect of regulating myopia and controlling the deepening of vision. Second, the principle of action of modern hyperopic defocusing mirror The concept of “one main cause and two key links” is the principle of action of modern hyperopic defocusing mirror: A large number of studies have shown that the occurrence and development of myopia in students is related to “one main cause and two key links The concept of “one major cause and two key links” is related. That is, the main cause of myopia in students is “looking at the near”, looking at the near mainly through the near reflex “peripheral visual field front defocus” and “adjustment lag” two key links to cause and aggravate myopia. Any myopia prevention method must control the “nearness” or the two key links in order to obtain good long-term results. Farsighted defocusing lenses can offset the main cause of myopia by optically shifting the near focus to the far side, and can also block the two key aspects of myopia: “near reflex defocusing” and “adjustment lag” by providing farsighted defocusing or training eye adjustment sensitivity. “and the “adjustment lag” link. Since its effect is a curative one, the long-term effect is better. Animal experiments: Studies on a large number of animal models of myopia such as rhesus monkeys by Zhongshan Eye Center (State Key Laboratory), University of New South Wales Vision Research Institute, Australia, and University of Houston College of Optometry, USA, have confirmed that the placement of myopic (negative) defocusing lenses in front of the eyes can cause and aggravate myopia, while the placement of hyperopic (positive) defocusing lenses can prevent the development of myopia. It is suggested that hyperopic defocusing lenses can prevent the occurrence and development of myopia. The modern hyperopic defocusing lenses can be divided into three main categories according to the way they distantly focus on “nearness”: 1) defocusing defocusing lenses (belonging to the second generation of basic myopia devices): they can virtualize the refractive focus when looking at nearness to a distance of 5 meters, directly offsetting the “nearness” which is the main cause of myopia in students. “This is the main reason for students’ myopia, and can provide hyperopic defocus (front defocus), blocking the first key link of myopia: “peripheral vision after defocus”, such as patch-type telephoto mirror, frame type telephoto mirror and table lamp type telephoto mirror. 2.Focusing distant mirror (belongs to the third generation of enhanced myopia instrument): can guide the eye refractive system for far-seeing and near-seeing focusing movement, so that the high focusing sensitivity when looking at the near, blocking the second key link of myopia “adjustment lag out of focus” caused by the occurrence and development of myopia. Such as eye sensitivity telecine or resonance sensitivity telecine. 3.Focus-shifting telephoto lenses (belonging to the 4th generation of enhanced myopia devices): they can shift the refractive focus of near vision to a distance of 5 meters away, directly offsetting “near vision” and providing progressively enhanced hyperopic defocus, blocking the first key link of myopia, “peripheral visual field after defocusing”. “It is a reinforcing type of defocusing lens because its effect can be reinforced in a relay manner. Such as automatic telephoto lenses. The defocusing, focusing and defocusing teleoptosis methods are the three most widely used and effective teleoptotic defocusing lenses in clinical practice.