Health Encyclopedia
Visual acuity test
Definition
The visual acuity test is used to determine the smallest letters a person can read on a standardized chart or card held 14 - 20 feet away.
Alternative Names
Eye test - acuity; Vision test - acuityHow the Test is Performed
This test may be done in a health care provider's office, a school, a work place, or elsewhere. Stand behind a line 20 feet from the eye chart. Remove glasses or contacts. 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. 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 any visual problems. Vision problems in young children can often be corrected or improved. Undetected or untreated problems may result in permanent damage to vision.
Normal Results
Visual acuity is expressed as a fraction. The top number refers to the distance you stand from the chart. This is usually 20 feet. The bottom number indicates the distance at which a person with normal eyesight could read the same line you correctly read. For example, 20/20 is considered normal. 20/40 indicates that the line you correctly read at 20 feet can be read by a person with normal vision from 40 feet away.
What Abnormal Results Mean
Abnormal results may indicate that you need corrective lenses to obtain normal vision, or may indicate an eye condition requiring further evaluation.
Related topics:
- Nearsightedness
- Farsightedness
- Presbyopia
- Amblyopia (lazy eye)
Risks
There are no risks.
Reviewed By: Manju Subramanian, MD, Assistant Professor in Ophthalmology, Vitreoretinal Disease and Surgery, Boston University Eye Associates, Boston, MA. Review provided by VeriMed Healthcare Network.
