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Q: Why must the subject stand 20 feet from the snellen eye chart?
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How is the snellen eye chart used to measure visual acuity?

20 feet


What is the purpose of a snellen chart?

The Snellen chart is the chart used by opticians to measure the sharpness of your eyesight (or visual acuity). It was developed by Dr Hermann Snellen in 1862. It has several lines of letters which get smaller as you go down the chart. The chart is placed level with the eyes at a distance of 20 feet (in Europe 6 metres). The standard reference eye is said to have 20/20 vision but this is not particularly good, any more than an IQ of 100 is good. If at 20 feet you can only just read letters that a person with "standard" eyes could read at 40 feet then you have 20/40 vision or if at 20 feet you can only just read letters that a standard eye could read at 60 feet then you have 20/60 vision and so on. If you can read the bottom line of very small letters on the Snellen chart your vision is an excellent 20/10. If you can read the third line from the bottom then it is a "standard" 20/20 which most people have fallen to by the age of 60.


What is the distance of snellen's test to the patient?

20 feet


How far do you have to stand away from the eye chart?

Stand about 20 feet away from the eye chart for optimal testing accuracy and precision when checking your vision. This distance ensures that the chart is viewed properly and helps in determining your visual acuity.


What does it mean if your vision is 40 20?

A person with 20/20 vision can read an eye chart at a distance of 20 feet. A person with 20/40 vision can't and has to get closer to the eye chart. A person with 20/20 vision can read at 40 feet what a person with 20/40 visionAnswerIf you have 20/40 vision, it means that when you stand 20 feet away from the chart you can see what a normal human can see when standing 40 feet from the chart. That is, if there is a normal person standing 40 feet away from the chart and you are standing only 20 feet away from it, you and the normal person can see the same detail. 20/100 means that when you stand 20 feet from the chart you can see what a normal person standing 100 feet away can see. 20/200 is the cutoff for legal blindness in the United States.


How is a visual acuity measured?

Snellen chart


Conversion Chart Acres to Square Feet?

I cannot provide a conversion chart but the formula is 1 acre = 43560 square feet.


When was Two Feet Stand created?

Two Feet Stand was created in 1996.


Where does Pisces point to on the chart of the human body?

feet


What do you stand with?

Your feet


To rise to your feet?

Terms meaning 'to rise to one's feet' include to 'stand', or 'stand up'.


Why do feet get ache if you stand longer?

Because some people stand long and there feet hert