what is 20/20 vision
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VISUAL ACUITY: WHAT IS 20/20 VISION?
Snellen Chart visual acuity is only one in a series of factors that evaluate one's vision.
20/20 vision is a term used to express normal visual acuity (the clarity or sharpness of vision) measured at a distance of 20 feet. If you have 20/20 vision, you can see clearly at 20 feet what should normally be seen at that distance. If you have 20/100 vision, it means that you must be as close as 20 feet to see what a person with normal vision can see at 100 feet. 20/20 does not necessarily mean perfect vision. 20/20 vision only indicates the sharpness or clarity of vision at a distance. There are other important vision skills, including peripheral awareness or side vision, eye coordination, depth perception, focusing ability and color vision that contribute to your overall visual ability. |
Some people can see well at a distance, but are unable to bring nearer objects into focus. This condition can be caused by hyperopia (farsightedness) or presbyopia (loss of focusing ability). Others can see items that are close, but cannot see those far away. This condition may be caused by myopia (nearsightedness).
The first eye chart was designed by the Dutch ophthalmologist Herman Snellen(1834-1908) whose Snellen Chart was imprinted with lines of black letters used to test the visual acuity of his patients. In 1843 the Test types were invented by Heinrich Kuechler (1811-1873) and were improved by the Vienna oculist Eduard Jaeger Ritter von Jaxtthal(1818-1884) in 1854. Shortly after this Snellen invented his chart of square shaped letters. This chart soon gained acceptance in all civilized countries. The Snellen fraction is a ratio measuring the visual acuity of a person's eyesight compared to a standard observer with good normal acuity. 20/20 means he can resolve 2 target features at 20 feet.
A comprehensive eye examination by a doctor of optometry can diagnose those causes, if any, that are affecting your ability to see well. In most cases, your optometrist can prescribe glasses, contact lenses or a vision therapy program that will help improve your vision. If the reduced vision is due to an eye disease, the use of ocular medication or other treatment may be used.
The first eye chart was designed by the Dutch ophthalmologist Herman Snellen(1834-1908) whose Snellen Chart was imprinted with lines of black letters used to test the visual acuity of his patients. In 1843 the Test types were invented by Heinrich Kuechler (1811-1873) and were improved by the Vienna oculist Eduard Jaeger Ritter von Jaxtthal(1818-1884) in 1854. Shortly after this Snellen invented his chart of square shaped letters. This chart soon gained acceptance in all civilized countries. The Snellen fraction is a ratio measuring the visual acuity of a person's eyesight compared to a standard observer with good normal acuity. 20/20 means he can resolve 2 target features at 20 feet.
A comprehensive eye examination by a doctor of optometry can diagnose those causes, if any, that are affecting your ability to see well. In most cases, your optometrist can prescribe glasses, contact lenses or a vision therapy program that will help improve your vision. If the reduced vision is due to an eye disease, the use of ocular medication or other treatment may be used.
WHAT'S YOUR 20?
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