Snellen fraction


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Snellen fraction

A representation of visual acuity in the form of a fraction (e.g. 6/6 (20/20), 6/24 (20/80), etc.) in which the numerator is the testing distance, usually expressed in metres (or in feet), and the denominator is the distance at which the smallest Snellen letter read by the eye has an angular size of 5 minutes. See near visual acuity; visual acuity; decimal visual acuity.
Table S3 Relationship between Snellen fractions in metres and feet, and for two testing distances (4 and 6 metres)
(6 m)(20 ft)(4 m)
6/320/104/2
6/4.820/164/3.2
6/620/204/4
6/7.520/254/5
6/9.520/324/6.3
6/1220/404/8
6/1520/504/10
6/1820/604/12
6/2120/704/14
6/2420/804/16
6/3020/1004/20
6/3820/1254/25
6/4820/1604/32
6/6020/2004/40
6/9020/3004/60
6/12020/4004/80
6/15020/5004/100
6/18020/6004/120
6/24020/8004/160
6/30020/10004/200