To test distance vision, individuals stand 20 feet from the Snellen eye chart, cover one eye, read aloud the smallest line they can clearly see, and then repeat this process with the other eye, states MedlinePlus. To test near vision, a smaller chart is held 14 inches from the face.
Individuals who wear glasses or contact lenses are typically required to remove them when having their vision tested, states MedlinePlus. Sometimes the test is repeated to check the individual's vision while wearing glasses or contact lenses. Special eye charts are available for people who are unable to read or identify letters. Vision tests are not uncomfortable, require no special preparation and are usually performed in health clinics, offices, schools or workplaces.
After performing an eye test, a person's visual acuity is written as a fraction. Normal vision is defined as 20/20 visual acuity, which means at 20 feet away from the eye chart, the person is able to read the line that most human beings with normal vision can read at 20 feet away, explains All About Vision. To get a driver's license, individuals must have a visual acuity of 20/40 or better, which may include the use of contact lenses or glasses.