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A person taking the test covers one eye from 6 metres or 20 feet away, and reads aloud the letters of each row, beginning at the top. The smallest row that can be read accurately indicates the visual acuity in that specific eye. The symbols on an acuity chart are formally known as "optotypes". Variation of Snellen chart with another letter ...
Snellen's eye chart became the first of its type, hence it being the most scientifically reliable design in order to test vision distance in that time period. [6] Snellen's success within his charts was because they differed from past models that measured visual acuity. His chart varied the sizes of stimuli. [10] Snellen's eye chart opened the ...
Near visual acuity or near vision is a measure of how clearly a person can see nearby small objects or letters.Visual acuity in general usually refers clarity of distance vision, and is measured using eye charts like Snellen chart, LogMAR chart etc. Near vision is usually measured and recorded using a printed hand-held card containing different sized paragraphs, words, letters or symbols.
Herman Snellen, a Dutch ophthalmologist, publishes in Utrecht his book, Probebuchstaben zur Bestimmung der Sehschärfe [Test letters for measuring visual acuity, containing charts for measuring visual acuity. [14] In later editions of his book, Snellen called the letters of his charts optotypes and advocated for standardized vision tests. [15]
Visual acuity VA Dcc - VA Dsc Visual acuity with Distant chart with correctors Visual acuity with eye chart at Distant 20 feet (6 m) and with (cc: Latin cum correctore) correctors (spectacles); Dsc is without (sc: Latin sine correctore) correctors. See Visual_acuity#Legal_definitions: VA Nsc - VA Ncc Visual acuity with Near chart without correctors
The chart was designed by Ian Bailey [5] and Jan E. Lovie-Kitchin at the National Vision Research Institute of Australia. [1] [3] They described their motivation for designing the LogMAR chart as follows: "We have designed a series of near vision charts in which the typeface, size progression, size range, number of words per row and spacings were chosen in an endeavour to achieve a ...