Because Dry Eye Syndrome can affect vision, a Snellen eye chart is used to test visual acuity — clearness or sharpness of vision.
One eye is closed or covered, and the letters and numbers on the chart are read off, starting with larger characters, and moving progressively to smaller characters.
Visual acuity is expressed as a fraction e.g.: 20/20.
- The top number indicates the distance from the chart
- The bottom number indicates from which distance a personal with normal vision can read the same line
For example, 20/20 is normal vision. 20/40 indicates that the characters read from 20 feet away can be read from 40 feet away by someone with normal vision.
