Where is the eye chart light box hanging in the infirmary?

According to the classification of the eye chart, the five-meter E meter is generally used in the infirmary, and can be hung on any wall, and a mirror is hung on the opposite wall. The testee sat under the chart with his back to the chart and read through the reflection in the mirror. The distance from the subject to the mirror+the distance from the mirror to the eye chart is 5 meters.