What does eyesight chart and myopic degree mean

Eye chart is usually to go to the hospital to check vision, the doctor most commonly used to check the vision chart. This chart is mostly called E word table, its direction is not the same. The eye chart can find out the eye's vision, through the eye chart to check. There is also a kind of called do degree, eye vision degree, this needs refraction, check the strength of the eye to the bending power of light, this degree has myopia degree, there are hyperopia degrees, there are astigmatism degrees, collectively known as do refractive error degrees. Myopia is expressed in negative degrees, say 200 degrees myopia. If hyperopia is expressed in positive degrees, this is the difference between degrees and vision. There is no strict correlation between degrees and vision.