Eyes / Ophthalmologists

Vision Test

In general, when someone mentions a vision test, they are referring to obtaining standard readings by identifying figures on an eye chart. Professionals call this a visual acuity test. It may be as simple as a poster taped to the wall or as sophisticated as computerized equipment that provides a variety of tests.

Almost without exception, the visual acuity test involves test objects (usually letters) that get progressively smaller. You are asked to identify the smallest figures that you are able to see.

The visual acuity exam often includes your vision with and without glasses at near (with a hand-held card) and at a distance. By convention, each eye is tested separately, although some practitioners will test the eyes together as well.

You’ve no doubt heard the term “20/20” as a way of referring to “perfect vision.” What does 20/20 mean? The first 20, which remains constant, refers to the distance from the eye to the chart. (While all exam rooms are not 20 feet, the letters are calibrated to simulate 20 feet.) The second number is the actual measurement. Thus, 20/20 is the size of letters that a “perfect” eye can see from a distance of 20 feet. A person with 20/40 vision sees, at 20 feet, what the normal eye could see at 40 feet. The larger that second number, the poorer the vision. 20/400 indicates that the person sees at 20 feet what the normal eye could see from 400 feet away.

Jan Ledford, COMT
EyeWrite Productions