The eye chart is a chart used to measure vision. The visual acuity charts used in China are: international standard visual acuity chart, logarithmic visual acuity chart, Landolt ring visual acuity chart. From the functional point of view, there is a near vision chart and a far vision chart. The eye chart is based on the principle of perspective. Check vision is generally divided into distance vision and near vision. Distance vision usually uses the international standard vision chart. This chart is composed of 14 rows of "E" with different opening directions in different sizes; the measurement ranges from 0.1-1.5 (or 4.0 from 4.0). -5.2); each line has a label, and the line of the subject’s visual acuity chart operation method should be parallel to the 1.0 line and 5 meters away from the visual acuity chart.