Definition of Visual acuity test:

The visual acuity test is used to determine the smallest letters a person can read on a standardized chart (Snellen chart) or a card held 14 - 20 feet away.

How the test is performed:

This test may be done in a health care provider's office, a school, a workplace, or elsewhere.

You will be asked to remove your glasses or contact lenses and stand or sit 20 feet from the eye chart. You will keep both eyes open.

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 you can see on the chart. Numbers or pictures are used for people who cannot read, especially children.

If you are not sure of the letter, you may guess. This test is done on each eye, one at a time. If needed, it is repeated while you wear your glasses or contacts. 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.

How to prepare for the test:

No special preparation is necessary for this test.

How the test will feel:

There is no discomfort.

Why the test is performed:

The visual acuity test is a routine part of an eye examination or general physical examination, particularly if there is a change in vision or a problem with vision.

In children, the test is performed to screen for vision problems. Vision problems in young children can often be corrected or improved. Undetected or untreated problems may lead to permanent vision damage.

There are other ways to check vision in very young children, or in people who do not know their letters or numbers.