The standard visual acuity chart is divided into a near visual acuity chart and a distant visual acuity chart according to

the measuring distance and measurement function. The measuring distance of the near visual acuity chart is 25 cm,

which measures the near vision; the distance visual acuity chart measures the distance of 5 meters, which measures the

distant vision. Everyone The most familiar and commonly used is the distance chart. However, the revised far and near

visual acuity chart has increased the number of optotypes, improved the uniformity of the alignment of optotypes, and

enhanced the accuracy and convenience of visual acuity testing.

The visual acuity chart is designed based on the principle of viewing angle. The so-called angle of view is the angle

formed by the light from two external points passing through the nodes in the eye. Under normal circumstances, the

human eye can distinguish the minimum angle of view formed by the smallest distance between two points, that is,

one point of view. The eye chart is designed in units of one point of view.