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Eye Library / Diagnostic Tests / Visual Acuity Testing

Visual acuity testing is a simple and important component of a comprehensive eye exam. An eye exam measures a person's ability to see an object at a specified distance. The results of an eye exam determine if a person has normal vision or if a prescription for glasses or contact lenses would help put things into proper focus.

This test may be done in a health care provider's office, a school, a work place,or elsewhere. No special preparation is necessary for this test. There is no discomfort. Removal glasses or contacts are required. Keep both eyes open and gently cover one eye with the palm of your hand, a piece of paper, or a paper cup while you read out loud the smallest line of letters that you can read on the chart. If you are not sure of the letter, you may guess. This test is done on each eye, one at a time. If necessary, it is then repeated while you wear your glasses or contacts.

Visual acuity is expressed as a fraction. 20/20 means "normal vision". If you can read the 20/40 line, that means that at 20 feet, you can see what a person with normal vision can see at 40 feet.

You may also be asked to read letters or numbers from a card held 14 inches from your face. This will test your near vision.