Using a Snellen Eye Chart Video Demonstration

Video Details: Video information on the proper use and setup of a Snellen eye chart, a chart used by eye care professionals to measure visual acuity. The chart consists of 11 lines of block letters, beginning with a large single letter on the top row. The number of letters on each row increases moving from top to bottom. The size of the letters progressively decreases, allowing for more letters on each subsequent line. The traditional Snellen eye chart only makes use of the following letters: C, D, E, F, L, O, P, T and Z. The chart is usually read while standing at a distance of 20 feet. Acuity is represented as a fraction, with the distance at which you are standing being the numerator (top part of fraction), and the normal maximum legible viewing distance ("Distance" on the chart above) as the denominator (bottom of fraction). So if, at 20 feet, you can read the letters on the row marked "40", this means you have visual acuity of 20/40 or better: 1/2 normal. From 10 feet, if the smallest letters you could read were on the "40" line, this would give you an acuity of 10/40: 1/4 normal. If you are nearsighted, your vision will become more normal the closer you stand to the chart.

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