Snellen's test type
The letters on the familiar eye chart used to measure how well you see at various distances. The eye chart, known as Snellen's chart, is imprinted with block letters that line-by-line decrease in size, corresponding to the distance at which that line of letters is normally visible. The block letters, Snellen's test type, are quite scientific in design (so that at the appropriate distance each letter subtends a visual angle of 5 degrees and each component part subtends an angle of 1 minute). The chart and the letters are named for a 19th-century Dutch ophthalmologist Hermann Snellen (1834-1908) who came up with them as a test of visual acuity. Visual acuity refers to the clarity or clearness of the vision, a measure of how well a person sees. The word "acuity" comes from the Latin "acuitas" = sharpness.

Medical dictionary. 2011.

Look at other dictionaries:

  • Snellen's chart — The familiar eye chart used to measure how well you see at various distances. Snellen s chart is imprinted with block letters that line by line decrease in size, corresponding to the distance at which that line of letters is normally visible. The …   Medical dictionary

  • Chart, Snellen's — The familiar eye chart used to measure how well you see at various distances. Snellen s chart is imprinted with block letters that line by line decrease in size, corresponding to the distance at which that line of letters is normally visible. The …   Medical dictionary

  • Eye chart, Snellen's — The familiar eye chart used to measure how well you see at various distances. Snellen s chart is imprinted with block letters that line by line decrease in size, corresponding to the distance at which that line of letters is normally visible. The …   Medical dictionary

  • Test, visual acuity — This test measures how well you see at various distances. It is the familiar eye chart test. The eye chart itself the usual one is called Snellen s chart is imprinted with block letters that line by line decrease in size, corresponding to the… …   Medical dictionary

  • Test, eye chart — This test measures how well you see at various distances. The eye chart itself the usual one is called Snellen s chart is imprinted with block letters that line by line decrease in size, corresponding to the distance at which that line of letters …   Medical dictionary

  • Acuity test, visual — This test measures how well you see at various distances. It is the familiar eye chart test. The eye chart itself the usual one is called Snellen s chart is imprinted with block letters that line by line decrease in size, corresponding to the… …   Medical dictionary

  • Visual acuity test — This test measures how well you see at various distances. It is the familiar eye chart test. The eye chart itself the usual one is called Snellen s chart is imprinted with block letters that line by line decrease in size, corresponding to the… …   Medical dictionary

  • Eye chart test — This test measures how well you see at various distances. The eye chart itself the usual one is called Snellen s chart is imprinted with block letters that line by line decrease in size, corresponding to the distance at which that line of letters …   Medical dictionary

  • Visual acuity — 20/15 and 20/15 vision redirect here. For other uses, see 2020 (disambiguation). Typical Snellen chart used for visual acuity testing. Visual acuity (VA) is acuteness or clearness of vision, which is dependent on the sharpness of the retinal… …   Wikipedia

  • List of instruments used in ophthalmology — Instruments used specially in Ophthalmology are as follows: [1] Contents 1 Instrument list 2 Image gallery 3 References Instrument list …   Wikipedia

Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”