20/20 Vision and Visual Acuity

20/20 vision is a measurement of visual acuity. 20/20 visual acuity means that a person can see small detail from 20 feet away the same as a person with normal eyesight would see from 20 feet. If a person has a visual acuity of 20/40, he is said to see detail from 20 feet away the same as a person with normal eyesight would see it from 40 feet away.

Eye glasses sitting on an eye exam chart
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Dutch ophthalmologist, Herman Snellen developed Snellen visual acuity in 1862. Snellen visual acuity is measured as a fraction and is represented as the distance at which the test is performed over the distance at which the smallest optotype identified subtends an angle of 5 minutes of arc and the detail of that optotype subtends 1 minute of arc. An optotype is a standardized letter, shape, picture or number used to show the subject whose visual acuity is being measured. 

20/20 vision is considered normal but it does not necessarily mean perfect vision. Having 20/20 vision only indicates the clarity of vision at a distance. It says nothing about the quality of vision and skills needed to have good vision, such as eye-hand coordination, accommodative ability, depth perception, peripheral vision, or color vision.

Furthermore, having 20/20 vision does not necessarily mean your eye is healthy. One can be farsighted, but still measure 20/20 visual acuity with no glasses on. Farsighted people sometimes have the ability to focus harder and compensate for the farsightedness. However, holding it there for a long period of time is exhausting and eventually, vision becomes blurry.

20/20 vision is considered normal vision. It is possible to have vision superior to 20/20: the maximum acuity of the human eye without visual aids (such as binoculars) is generally thought to be around 20/10.

Other Ways to Measure Visual Acuity

"Tumbling E" Visual Acuity Chart: How do you measure visual acuity in someone that can't speak or is maybe just too shy to speak? The Tumbling E chart uses the same measurement scale as the typical Snellen Eye Chart. However, all of the optotypes used on the chart are a capital E but displayed in different orientations. In this case, a person being shown a letter to read on the eye chart can simply use his or her fingers and show the tester what direction the E is pointing.

LEA Vision Test: The LEA test is a visual acuity test designed for children who can not read letters. The test uses for optotypes: an apple, a pentagon, a square, and a circle. The test uses these common symbols so that visual acuity can be measured at a much younger age.

Jaeger Eye Chart for Near Vision: If you have had an eye examination, you may have been shown a Jaeger eye chart to test your near visual acuity. The Jaeger chart is a small handheld chart that shows blocks of text in various sizes. Instead of using the term 2/20, The Jaeger chart uses a scale that ranges from J1 to J11. J2 is usually considered equal to the typical 20/20 measurement. The chart is usually head between 12-16 inches from your eyes.

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  1. American Optometric Association. Visual acuity.

  2. Mbagwu M, French DD, Gill M, et al. Creation of an accurate algorithm to detect snellen best documented visual acuity from ophthalmology electronic health record notesJMIR Med Inform. 2016 Jun;4(2):14. doi:10.2196/medinform.4732

  3. Yeung WK, Dawes P, Pye A, et al. eHealth tools for the self-testing of visual acuity: a scoping review. Nature Partner Journals. Aug 2019;2(82):1-6. doi:10.1038/s41746-019-0154-5