Mr. Zhang, 45, who was not nearsighted, felt a little blurry reading newspapers and books since this year. After coming to the hospital for a checkup, the doctor told him that his eyes were a little presbyopic and that a pair of presbyopic glasses would do. Mr. Wang is a little confused, 60-year-old colleague Li myopia for more than 30 years, but so far to see near are not required to wear glasses, this is why? In fact, Mr. Wang this problem is very common. The so-called myopia refers to the parallel light into the eye after imaging in front of the retina, resulting in unclear retinal imaging, clinical performance is to see near things clear, see far is not clear. As we age, generally after the age of 40, due to the weakening and hardening of the lens of the eye, its adjustment function is weakened, and the visual impairment phenomenon of not being able to see objects at close distances but relatively being able to see objects at a distance is called presbyopia, commonly known as presbyopia. This is caused by the aging of the whole body and eye tissue, abnormal metabolism of fibrous proteins in the eye lens, loss of water, hardening of texture, loss of elasticity, and weakening of accommodation power. Presbyopia is a physiological phenomenon that occurs in everyone, regardless of the usual refractive state. However, the original refractive state will affect the time of onset of presbyopia symptoms, with uncorrected farsighted people experiencing presbyopia earlier and myopic people experiencing it later. The eye needs a certain distance to see objects. The point at which the eye can see the nearest object is called the near point. Since myopic people have a closer near point than normal, presbyopes have a farther point than normal. Therefore, nearsighted people have presbyopia in old age, and when they look closer, the near point is relatively shifted back, so it is shown that nearsightedness can offset some of the presbyopia. However, what myopia and presbyopia can offset is only the part of “seeing close”. It is still the same when you look far away. Moreover, presbyopia is only 300-350 degrees at most (400 degrees or more is rare), so it can only offset 300-350 degrees of myopia. If a person has 300 degrees of myopia and 300 degrees of presbyopia at the same time, then he needs to wear 300 degrees of nearsighted glasses to see far, while he does not need presbyopia glasses to see near objects. This is the case of the old man Li who was talked about earlier. But if you have 600 degrees of myopia and 200 degrees of presbyopia, you need to wear 600 degrees of glasses for near vision and 400 degrees of glasses for presbyopia. In short, the law of myopia with presbyopic glasses is: the algebraic sum of myopia and presbyopia degrees. If the 50-year-old original 300 degrees of myopia with presbyopia: -300 + (+200) = -100, that is, when looking at the near need to match 100 degrees of myopia lenses. The principle of prescription for presbyopic lenses is: first of all, a distance vision examination and optometry should be conducted to understand the refractive state, as well as to understand the nature of the work and reading habits of the examinees, and choose the appropriate reading distance for presbyopic prescription. The correction of presbyopia should be done with convex lenses, and single-light glasses, bifocal glasses and gradient multifocal glasses can be chosen. This shows that anyone needs to prevent presbyopia. Pay attention to dietary nutrition, more protein, more food rich in vitamin A, such as carrots, etc. Strengthen exercise and improve physical fitness. According to Chinese medicine, “the liver is open to the eyes”. Liver and kidney are the same source, liver and kidney deficiency, the eyes are not nourished, then the vision is faint, so usually can be appropriate oral supplementation of liver and kidney drugs, such as bright eyes Dihuangwan, Qiju Dihuangwan, etc.. In addition, special attention should be paid to eye hygiene, do not read at close range for a long time, and ensure sufficient light when reading books to reduce lens adjustment force fatigue and prevent inadequate adjustment function.