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  2. Snellen chart - Wikipedia

    en.wikipedia.org/wiki/Snellen_chart

    Snellen chart. Purpose. Snellen chart is used to estimate visual acuity (last three rows are 20/15, 20/13 and 20/10) 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 ...

  3. Visual acuity - Wikipedia

    en.wikipedia.org/wiki/Visual_acuity

    In the expression 6/x vision, the numerator (6) is the distance in metres between the subject and the chart and the denominator (x) the distance at which a person with 6/6 acuity would discern the same optotype. Thus, 6/12 means that a person with 6/6 vision would discern the same optotype from 12 metres away (i.e. at twice the distance).

  4. LogMAR chart - Wikipedia

    en.wikipedia.org/wiki/LogMAR_chart

    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 ...

  5. Eye chart - Wikipedia

    en.wikipedia.org/wiki/Eye_chart

    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]

  6. Minute and second of arc - Wikipedia

    en.wikipedia.org/wiki/Minute_and_second_of_arc

    The nautical mile (nmi) was originally defined as the arc length of a minute of latitude on a spherical Earth, so the actual Earth circumference is very near 21 600 nmi. A minute of arc is ⁠π 10 800⁠ of a radian . A second of arc, arcsecond (arcsec), or arc second, denoted by the symbol ″, [ 2] is ⁠ 1 60 ⁠ of an arcminute, ⁠ 1 3600 ...

  7. List of optometric abbreviations - Wikipedia

    en.wikipedia.org/wiki/List_of_optometric...

    Description ( notes ) AC. Anterior chamber. fluid-filled space between the iris and the endothelium. AC 4/4. Grade 4 anterior chamber angle. open angle between cornea and iris. AC 3/4. Grade 3 anterior chamber angle.

  8. Contrast (vision) - Wikipedia

    en.wikipedia.org/wiki/Contrast_(vision)

    Contrast (vision) Six renditions of a rocky shore photo with incremental contrast levels, clockwise from bottom left. Contrast is the difference in luminance or color that makes an object (or its representation in an image or display) visible against a background of different luminance or color. The human visual system is more sensitive to ...

  9. Field of view - Wikipedia

    en.wikipedia.org/wiki/Field_of_view

    The field of view ( FOV) is the angular extent of the observable world that is seen at any given moment. In the case of optical instruments or sensors, it is a solid angle through which a detector is sensitive to electromagnetic radiation. It is further relevant in photography .

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