The simpler, more intuitive and effective way to measure visual acuity is to use a visual acuity chart, which can clearly check the patient's refractive power. However, many people do not have a deep understanding of the conversion between visual acuity chart and power. As a result, refractive patients cannot expect the optician to provide accurate diopter during the process of fitting glasses, which affects the effect of vision correction. So how do the visual acuity chart and the degree are converted? The following editor will take you to find out. The visual acuity chart and the conversion of the degree of visual acuity chart are designed based on the principle of viewing angle. The so-called viewing angle is the angle formed by the light from two external points through the nodes in the eye. Under normal circumstances, the human eye can distinguish that the viewing angle formed by the small distance between two points is a smaller viewing angle, that is, a one-point viewing angle. However, the eye chart is designed in the unit of one-point viewing angle, and the conversion is also based on This viewing angle is used to determine the diopter. For example, 1 diopter is defined as the focal point formed one meter behind the lens. If the focal length from the lens is 0.5 meters, then the diopter of the patient is 200 degrees. In general, the patient rules for eye chart and degree are: old 0.1-new 4.0u003d650, old 0.12-new 4.1u003d550~600, old 0.15-new 4.2u003d500, old 0.2-new 4.3u003d450, old 0.2-new 4.4u003d400, old 0.3—new 4.5u003d300~350, old 0.4—new 4.6u003d250, old 0.5—new 4.7u003d200, old 0.6—new 4.8u003d150, old 0.8—new 4.9u003d100. These are the more common rules for conversion between the eye chart and the power. They are only for your reference and cannot be used as the rules for determining the power. The detailed refractive power is better after professional optometry. Generally speaking, people with refractive errors have poor vision. The higher the refractive power, the lower the naked vision and the lower the clarity of vision. But it is not absolute. Some people's refractive power is not high, but their vision is very low, because it is not only the refractive power that affects the quality of vision, but also has a great relationship with other diseases of the eye. For example, if the retinal imaging function of the eye or the optic nerve function is damaged, it will also cause vision loss. Therefore, for patients with diopter, it is better not to determine the diopter based on the eye chart alone, but to go to a more formal optician for refraction, and then wear appropriate frame glasses for correction.