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A Snellen chart is an eye chart that can be used to measure visual acuity. Snellen charts are named after the Dutch ophthalmologist Herman Snellen who developed the chart in 1862 as a measurement tool for the acuity formula developed by his professor Franciscus Cornelius Donders. [1] [2] Many ophthalmologists and vision scientists now use an ...
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.
An example of the Landolt C eye chart (also known as the Japanese eye chart.). Numerous types of eye charts exist and are used in various situations. For example, the Snellen chart is designed for use at 6 meters or 20 feet, and is thus appropriate for testing distance vision, while the ETDRS chart is designed for use at 4 meters. [16]
Normal" visual acuity (in central, i.e. foveal vision) is frequently considered to be what was defined by Herman Snellen as the ability to recognize an optotype when it subtended 5 minutes of arc, that is Snellen's chart 6/6-metre, 20/20 feet, 1.00 decimal or 0.0 logMAR.
See Visual_acuity#Legal_definitions: VA Nsc - VA Ncc Visual acuity with Near chart without correctors Visual acuity with eye chart at Near 15.7 inches (400 mm) and without (sc: Latin sine correctore) correctors (spectacles); Ncc is with (cc: Latin cum correctore) correctors. See Visual_acuity#Legal_definitions: VA OS Left visual acuity VA OD
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 ...
Whereas for adults a small Snellen chart letter or number can be used. [1] Distance Targets (6m) Spotlight – In those patients with amblyopia a spotlight could be used. (Same as near targets). [1] Snellen chart – This is the most commonly used target when assessing a patient's far component of a cover test. [1]
••Snellen's near chart (1/17th reduction of distant chart)-do-; standard chart of alphabets; video link •Colour vision: to test colour vision ••Ishihara's chart: to determine the type of colour blindness Stenopaeic slit: detection of axis of the cylindrical (astigmatism) power of the eye; glaucoma testing Implants - •Intraocular lens