Visual acuity test
Alternative Names: Vision test Snellen’s chart test
A visual acuity, or vision, test measures how well you can see in the distance (not near or reading vision). It may be done as part of a routine screening procedure or to examine eye problems. It cannot differentiate, however, between the possible causes of poor vision (such as short-sightedness, cataracts, or retinal detachment). The test involves reading letters or symbols on a chart. If the doctor cannot correct your poor vision with spectacles, further testing may well be necessary.
What is it?
A visual acuity test is a test to measure how well a person can see. It measures distant vision, not near vision or vision used for reading.
Visual acuity test can be performed wherever there is a suitable chart – commonly in your doctor’s rooms, at the optician, in schools, and in clinics or hospitals.
Why is it done?
Visual acuity testing is done to assess vision, either as a routine screening procedure or as part of a more complete eye examination in those with eye problems. It will measure how well a person sees but, if the vision is poor, it will not differentiate between the possible causes of poor vision (which range from simple refractive errors, such as short-sightedness, that need spectacles to more serious eye conditions like cataracts or retinal detachment).
What happens?
Before – how to prepare
No special preparation is necessary.
During – how the test is done
You stand 6 metres from the chart and, while covering one eye at a time, attempt to read the letters on the chart (other symbols are used for those who cannot read).
The result is expressed as a fraction, with 6 (the distance from the chart) the top number. The lower number is the distance a normally sighted person can read the letters you were able to read at 6 metres. Thus, 6/6 is normal and 6/30 means that you read at 6 metres, what a normally sighted person reads at 30 metres.
Risks and Compilations
There are no risks associated with this procedure.
Special Issues
To determine the cause of any vision problems, further examination and testing may well be necessary. However, simple refractive errors are the most common cause of poor vision and so many doctors will simply attempt to correct your vision by using spectacle lenses. If such lenses are able to correct your vision (to 6/6), it is probably reasonable to assume the problem is indeed a refractive error.
Short Description
A visual acuity, or vision, test measures how well you can see in the distance (not near or reading vision).
Keywords
visual acuity test, vision test, Snellen’s chart test, eye test, eyesight test