20 100 Vision Chart

Vision Without Glasses

What is 20/20 Vision?

If you have what has been determined as humanity's anormala eyesight, you have 20/20 vision. In countries which use metric measurements, it is called 6/6 vision, referring to meters instead of feet. 20/20 vision is not aperfecta vision, but it is clear at all distances, needing no glasses or contact lenses. Vision can be better than 20/20, so let's look at that further down this article.

The Snellen Eye Chart

Most of us are familiar with that eye chart which has a single large letter at the top (usually an

aEa) and rows of progressively smaller letters below it. There are some variations on the most common version of this chart. In all versions, one line is designated as the anormal visiona line and the others te 00004000 st your vision relative to that anormala line.

When your eye doctor tests your vision for a glasses or contact lens prescription, the eye chart is seen through an ophthalmic device called a phoropter. You rest your chin and forehead against smooth surfaces and look with one eye at a time at the lighted chart inside the aperture.

There are also printed charts that can hang on the wall, and these can test your vision too, but the phoropter is more precise. Instead of you having to physically stand a certain distance away from it, distance is simulated by the phoropter's optics.

From Twenty Feet Away

Normality is defined as a clear perception of the designated anormala line of letters at 20 feet from the eye chart. That is the first a20a. The second number, which may or may not be a20a is a comparison between the tested eye and a anormala eye. The higher the second number is, the more vision impairment your eyes have.

If a normal eye can see from 40 feet away what you must stand only 20 feet away to see, your vision is described as a20/40a.

If a normal eye can see from 100 feet away what you can only see if you stand 20 feet away, your vision is a20/100a.

If your vision is described as a20/200a, you are legally blind.

To describe this another way, imagine you moving back and forth from the eye chart, trying to see the anormala line clearly. If you can see it clearly from 20 feet away, your eyesight is 20/20. If you must edge closer to the chart to see it, your vision is impaired and you are nearsighted.

But ophthalmologists don't usually measure those closer distances in defining your visual acuity. They talk in terms of further distances and postulate that the tested eye is always at 20 feet from the chart. They then compare that amount of acuity with what a normal eye has at varying distances. When the normal eye can see from 80 feet what you see at 20 feet, your vision is 20/80.

Vision Better Than aNormala

If your vision is 20/16 you can see from 20 feet away what a anormala eye can only see from 16 feet. That is better visual acuity than what we consider to be normal.

After a Custom LASIK surgery many people can see with 20/16 clarity. Their vision has been made better than humanity's normal vision. Custom LASIK is based on a more sophisticated and accurate diagnosis than the original Traditional LASIK was. A Custom LASIK procedure does more than just correct nearsightedness, farsightedness and/or astigmatism (that is, the three Lower Order Aberrations).

It also corrects the tiny irregularities called Higher Order Aberrations. A phoropter is not used to diagnose your eyes for Custom LASIK. Instead, a newer technology is used called Wavefront technology. It shines a light into each eye and measures the slight changes in it as it reflects back from your eye into the Wavefront system. From the resulting colored 3-D maps of each eye's contours, your LASIK surgeon can plan a more precise treatment.

When the Custom LASIK laser smoothes out these microscopic irregularities in the eye's cornea (clear front part), your vision improves beyond what glasses or contact lenses can achieve. This is how a person can achieve 20/16 vision - better than normal. The Higher Order Aberrations cause visual distortions which show up in dim light, such as halos around light sources, decreased contrast between light and dark, and faint duplicate images. When these are corrected, your vision is clearer in all lighting conditions.

About the author: If you are in the Calgary, Alberta area and would like to know more about your eyes and how your vision could be improved, please contact Western Laser Eye Associates, where Dr. Anderson Penno will give you top quality service.

Source: http://www.articlesbase.com/vision-articles/what-is-2020-vision-691769.html


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10 Responses to 20 100 Vision Chart

  1. ☮, ♥. Satisfaction. says:

    My vision is 180/100…how bad is it?
    And he said something about astigmatism and 575, but apparently I can only see 20/30 with my glasses ON.

    So.
    Does anyone know what 180/100 vision is (how bad) and a chart where I can see optical…stuff. xD
    Um, he said 180/100 in accordance with 20/20.

    • Footprintz says:

      I think you heard bits and pieces of a bunch of numbers and got them all confused.

      180/100 doesn’t really make any sense in optical terms . ( where did you see that ? )

      ” Something about astigmatism and 575 ” doesn’t really say much either.

      575 on it’s own doesn’t mean anything either.

      Sooo, in other words, you don’t have enough clear information to be able to answer to.

      If that was a 5.75 cyl for astigmatism, your vision would be much worse that 20/180 or 20/100 , which may be the other part.

      All in all…not enough clear info, sorry.

  2. one who enjoys learning says:

    Snellen eye chart – is visual acuity from a 10-ft chart as opposed to a 20-ft chart that much different?
    Environment (molecules in the air) can play a role in how accurate our measurements are if we were to compare a visual acuity of 10/20 to a vision acuity of 50/100, for example.

    But is a measurement of 10/20 (from a 10 ft chart) identical or any different from a measurement of 20/40 (from a 20 ft chart), considering the very small distance between the two charts from the person?

    • greydoc6 says:

      Unless you’re testing in a London fog or a room that is ablaze, the 10 foot difference shouldn’t make a difference as far as atmospherics are concerned.

      The height of the letters are designed to subtend a visual angle of five minutes of arc at the specified distance. The width of the lines in the letters, and the width of their separation – the opening of the letter C, for example – and the lengths of the serifs subtend an angle of one minute of arc. Thus the letters on the 20/20 line at 20 feet subtend the same angle as the letters on the 20/40 line when read at 40 feet.

  3. Anonymous says:

    Is it true that if your vision is worst than 20/100 that they just automatically say its 20/200?
    My doctor told me that because my vision is worst than 20/100 that they just call it 20/200 even though my vision is obviously not that bad because they don’t bother testing for 20/125 or 20/150 etc.
    So basically if you can’t read at the 20/100 chart they just automatically say your vision is 20/200 even though it is probably not.
    Is this true?

    • Jmax says:

      Yes. There is no line on the Snellen chart for anything between 20/100 and 20/200. For most purposes there is little point in subdividing the standard increments for visual acuity. Although 20/200 looks twice as bad as 20/100 as a fraction, there is really little difference in visual efficiency between the two in reality. Like 20/200 represents about 85% of the visual efficiency of 20/100. Besides, your uncorrected VA isn’t used to work out your prescription.

  4. hi says:

    can someone tell me what eye vision is this?and give me a chart of all if u can?
    my eye vision the doctor said was 80 on left and 100 on right…what does that means?and can someone give me all the eye vision chart or some like 20/20 40/100 or w/e u call them

    • Menthoids says:

      The eye chart is called a Snellen Chart after the inventor. It is usually read while standing at a distance of 20 feet. Acuity (the visual accuracy) is represented as a fraction. 20/20 means that at 20 feet from the chart you can read the row marked 20 and that is normal vision.

      The distance you are standing from the chart is top part of fraction (or first number), and the maximum legible viewing distance is the bottom of fraction.

      So if, at 20 feet, you can read the letters on the row marked 40, this means you have visual acuity of 20/40 or better which is 1/2 normal.

      If at 10 feet, if the smallest letters you could read were on the 40 line, this would give you an acuity of 10/40 which is 1/4 normal.

      More info and picture at the link.

      Hope that helps.

  5. hemang p says:

    What does it mean if someone’s vision is described as being 20/100 according to the Snellen eye chart?
    What does it mean if someone’s vision is described as being 20/100 according to the Snellen eye chart?

    A. They have presbyopia
    B. They have hyperopia
    C. They have myopia
    D. They have cataracts

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