Vision Testing

Vision tests check many different functions of the eye. A complete evaluation of a person's eyesight involves tests that measure the ability to focus on and see details at near and far distances (visual acuity), check for gaps or defects in the field of vision, and evaluate the ability to see different colors. More specialized tests may be done, depending on the person's symptoms, age, and medical and family history.

Visual acuity tests are the simplest tests used to evaluate a person's eyesight. They measure the eye's focusing power and the person's ability to see details at near and far distances. The tests usually involve reading letters or looking at symbols of different sizes on an eye chart. Both eyes are always tested individually with and without corrective lenses and separate scores are recorded for each eye. The visual acuity exam may also include a refraction test which detects nearsightedness or farsightedness that occurs when light rays entering the eye do not focus exactly on the retina at the back of the eye. This leads to blurred vision. Refraction testing is done as a routine part of an eye exam for people who already wear glasses or contact lenses, but it will also be done if the results of the other visual acuity tests show that a person's eyesight is below normal and can be corrected by glasses.

A person's complete visual field is the entire area seen when the person's gaze is fixed in one direction. The complete visual field is seen by both eyes simultaneously and it includes the central visual field and side (peripheral) visual fields. Visual field tests can help detect eye diseases or nervous system problems that limit a person's ability to see objects clearly in the entire visual field or in one part of it.

Color vision testing checks a person's ability to distinguish colors and is often part of a routine eye exam. It is also used to screen for color blindness in people with suspected retinal or optic nerve disease or a family history of color blindness. The color vision test is also used to screen applicants for jobs in fields where color perception is essential, such as the military or electronics.

There is no pain and very little discomfort associated with most of these tests and these tests do not have any risks or complications.