What is the meaning of the WORTH four-dot reticle on the visual acuity chart?

That measures binocular vision. It has to be used with red and green filters. This is a very traditional method of ophthalmologic examination with a history of nearly 100 years. The English name is WORTH 4 dot. four holes, four dots, as the name implies, there are four image points. All four-hole lights, four-dot charts are composed of four image points, and are composed of red, green and white colors, which is also clearly differentiated from other eye examination equipment.

The visual acuity chart is designed according to the principle of angle of view. The so-called angle of view is the angle formed by the light emitted from two external points, through the nodes in the eye. Under normal circumstances, the human eye can distinguish the smallest distance between the two points formed by the angle of view for the smallest angle of view, that is, one point angle of view. The visual acuity chart is designed in units of one minute of visual angle.