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When printed out at this size, the E on line one will be 88.7 mm tall and when viewed at a distance of 20 ft, you can estimate your eyesight based on the smallest line you can read.}} |Source=Own work by uploader, Based
Some clinics do not have 6-metre eye lanes available, and either a half-size chart subtending the same angles at 3 metres (9.8 ft), or a reversed chart projected and viewed by a mirror is used to achieve the correct sized letters. In the most familiar acuity test, a Snellen chart is placed at a standard distance: 6 metres.
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 internationalised vector image was then created by User:Silversmith and uploaded to Commons as Image:Schematic diagram of the human eye.svg (see right). On request, this version with English annotations was created and uploaded here. Later, the text labels were made into hyperlinks pointing at relevant articles in the English Wikipedia.
A 1951 USAF resolution test chart is a microscopic optical resolution test device originally defined by the U.S. Air Force MIL-STD-150A standard of 1951. The design provides numerous small target shapes exhibiting a stepped assortment of precise spatial frequency specimens.
Cross section of a human eye, showing a detached retina at top. Date: 24 June 2009, 17:44 (UTC) Source: Schematic diagram of the human eye.svg: Author: Erin Silversmith from an original by en:User:Delta G. derivative work: RexxS; Other versions: Derivative works of this file: Human eye cross section detached retina-es.svg: SVG development
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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]