Presbyopia, or presbyopia, is a phenomenon in which the near vision is not sustained, and the lack of adjustment means that the near point gradually becomes farther and farther away, and the near object can be seen clearly after effort. As the eye grows older, the ability to adjust gradually decreases, causing patients to have difficulty seeing near, so that in close work, they must add a convex lens in addition to their static refractive correction in order to have clear near vision, a phenomenon known as presbyopia (presbyopia). The reasons why elderly people cannot sustain near vision are both physiological and pathological. The physiological factors are the reduced light transmission of the cornea, crystal and vitreous humor of the elderly; the reduced pupil size of the elderly, so that the light reaching the retina is weakened; the physiological aging of the visual path to the visual center function, etc. These physiological changes have obvious individual differences. However, most of them are caused by presbyopia or farsightedness that cause errors and blurring, so how can presbyopia and farsightedness be identified? In fact, presbyopia is a physiological phenomenon of aging with human age and does not belong to refractive error; while hyperopia is a disease of the eye and is a kind of refractive error. In people over 40 years old, the plasticity of the lens gradually decreases and tends to harden, the ciliary muscle becomes thinner, and the adjustment function is weakened, as a result of which the clarity of near objects becomes less and less, and the near point gradually shifts farther and farther. In the farsighted eye, after the refraction of the refractive system, the parallel light rays are focused behind the retina, forming a ring-shaped aperture on the retina, without a clear image, and becoming an imaginary focus after the retina. The age of presbyopia is generally not less than 40 years old; there is no age limit for hyperopia, and even children as young as six or seven years old can suffer from hyperopia. The degree of presbyopia in the left and right eyes is equal. The corrective lenses used are designed for near vision, so if the distance exceeds 0.3m, you will not be able to see clearly. Farsightedness in hyperopia can occur in one, both or both eyes to varying degrees. When corrected, farsighted glasses are not only used for seeing near, but also for seeing distant objects.