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Vision Tests

How It Is Done continued...

Color vision tests check your ability to distinguish colors. In the most commonly used color vision test, you look for different colored numbers or symbols hidden in varying backgrounds of colored dots.

First, you are shown sample patterns and told what symbols and numbers you can expect to see. You then sit at a table and cover one eye. The health professional holds the color test patterns about 14 in. (36 cm) away from you. Some patterns are harder to pick out than others. As the health professional holds up a pattern, you will identify the number or symbol you see and trace it using a pointer. Some patterns may not have a number or symbol. The test is then repeated with the other eye.

How It Feels

You should not feel any discomfort during these vision tests.

When dilating eyedrops are used

Dilating drops may make your eyes sting and cause a medicine taste in your mouth. You will have trouble focusing your eyes for up to 12 hours after your eyes have been dilated. Your distance vision usually is not affected as much as your near vision, though your eyes may be very sensitive to light. Do not drive for several hours after your eyes have been dilated. Wearing sunglasses may make you more comfortable until the effect of the drops wears off.

Risks

In some people, the dilating eyedrops can cause an allergic reaction.

Results

Vision tests check many different functions of the eye.

Visual acuity testing

The visual acuity score compares your distance vision with that of people who have normal vision, using an eye chart. Each eye's score is expressed as two numbers, such as 20/20 (6/6) or 20/100 (6/30). The first number is the distance you stand from the chart, usually 20 ft (6 m) when using a typical wall chart. The second number is the distance from which people with normal eyesight can read the same line on the eye chart.

20/20 (6/6) vision is considered normal. A person with 20/20 vision can see at 20 ft (6 m) what people with normal vision can see at this distance.

  • When the second number is smaller than the first number, the person's vision is better than normal. For instance, a person with 20/10 (6/3) vision can see from 20 ft (6 m) what people with normal vision can see from 10 ft (3 m).
  • When the second number is larger than the first number, the person's distance vision is worse than normal.
  • A person with 20/200 (6/60) vision or less in his or her best eye when wearing corrective lenses is considered legally blind.

WebMD Medical Reference from Healthwise

Last Updated: June 09, 2011
This information is not intended to replace the advice of a doctor. Healthwise disclaims any liability for the decisions you make based on this information.

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