20/20 vision - please explain
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20/20 vision - please explain
I understand the 20 feet at 20 feet thing, but how can someone be 20/20 for "near" vision?
My son just go checked and they listed his near vision at 20/20...... is that just to make it easier on people to understand? It clearly isn't 20 feet since that is the far sight test.
i tried to quickly look it up but couldn't find the answer.
thanks
My son just go checked and they listed his near vision at 20/20...... is that just to make it easier on people to understand? It clearly isn't 20 feet since that is the far sight test.
i tried to quickly look it up but couldn't find the answer.
thanks
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http://en.wikipedia.org/wiki/Visual_acuity
From what I understand, it's just a ratio, so it doesn't have to be 20 feet away.
I'm sure that S2020 will chime in with the right answer.
From what I understand, it's just a ratio, so it doesn't have to be 20 feet away.
I'm sure that S2020 will chime in with the right answer.
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Hey guys, I'm an ophthalmic tech so I thought I'd chime in.
The most commonly used format for recording VA's (visual acuities) is in Snellen notation, whether it be for distance or near testing. Snellen notation is recorded as 20/X, where 20 means test distance, and X is the line of acuity the patient can read. Lets say you read off the 20/200 line. A person with emmetropic vision (20/20) could see the 20/200 line at 200 feet, versus your 20 feet.
On to your question.. Near point acuities are also written in Snellen notation (20/X), and are done with a card that has to be held a certain distance from the eye (usually 14 inches). No matter what the testing distance, the vision will still be recorded as 20/X, since it is the most conventional way to see va's recorded.
Why do we record it as 20/20 even though its not at 20 feet?--just because its easier for us to comprehend and thats the way we've done it for years.
You can translate 14/y to 20/x mathematically if you wanna do it the hard way, but its conveniently printed on the card in Snellen notation.
Good job to your son for reading off the small line! Young eyes can accomodate so easily, now when you hit 40, it can be challenging.
The most commonly used format for recording VA's (visual acuities) is in Snellen notation, whether it be for distance or near testing. Snellen notation is recorded as 20/X, where 20 means test distance, and X is the line of acuity the patient can read. Lets say you read off the 20/200 line. A person with emmetropic vision (20/20) could see the 20/200 line at 200 feet, versus your 20 feet.
On to your question.. Near point acuities are also written in Snellen notation (20/X), and are done with a card that has to be held a certain distance from the eye (usually 14 inches). No matter what the testing distance, the vision will still be recorded as 20/X, since it is the most conventional way to see va's recorded.
Why do we record it as 20/20 even though its not at 20 feet?--just because its easier for us to comprehend and thats the way we've done it for years.
You can translate 14/y to 20/x mathematically if you wanna do it the hard way, but its conveniently printed on the card in Snellen notation.
Good job to your son for reading off the small line! Young eyes can accomodate so easily, now when you hit 40, it can be challenging.
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Originally Posted by jamesk,Nov 20 2006, 10:10 AM
Hey guys, I'm an ophthalmic tech so I thought I'd chime in.
The most commonly used format for recording VA's (visual acuities) is in Snellen notation, whether it be for distance or near testing. Snellen notation is recorded as 20/X, where 20 means test distance, and X is the line of acuity the patient can read. Lets say you read off the 20/200 line. A person with emmetropic vision (20/20) could see the 20/200 line at 200 feet, versus your 20 feet.
On to your question.. Near point acuities are also written in Snellen notation (20/X), and are done with a card that has to be held a certain distance from the eye (usually 14 inches). No matter what the testing distance, the vision will still be recorded as 20/X, since it is the most conventional way to see va's recorded.
Why do we record it as 20/20 even though its not at 20 feet?--just because its easier for us to comprehend and thats the way we've done it for years.
You can translate 14/y to 20/x mathematically if you wanna do it the hard way, but its conveniently printed on the card in Snellen notation.
Good job to your son for reading off the small line! Young eyes can accomodate so easily, now when you hit 40, it can be challenging.
The most commonly used format for recording VA's (visual acuities) is in Snellen notation, whether it be for distance or near testing. Snellen notation is recorded as 20/X, where 20 means test distance, and X is the line of acuity the patient can read. Lets say you read off the 20/200 line. A person with emmetropic vision (20/20) could see the 20/200 line at 200 feet, versus your 20 feet.
On to your question.. Near point acuities are also written in Snellen notation (20/X), and are done with a card that has to be held a certain distance from the eye (usually 14 inches). No matter what the testing distance, the vision will still be recorded as 20/X, since it is the most conventional way to see va's recorded.
Why do we record it as 20/20 even though its not at 20 feet?--just because its easier for us to comprehend and thats the way we've done it for years.
You can translate 14/y to 20/x mathematically if you wanna do it the hard way, but its conveniently printed on the card in Snellen notation.
Good job to your son for reading off the small line! Young eyes can accomodate so easily, now when you hit 40, it can be challenging.
Learn something new everyday.
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From: Nashville
Originally Posted by jamesk,Nov 20 2006, 10:10 AM
Hey guys, I'm an ophthalmic tech so I thought I'd chime in.
The most commonly used format for recording VA's (visual acuities) is in Snellen notation, whether it be for distance or near testing. Snellen notation is recorded as 20/X, where 20 means test distance, and X is the line of acuity the patient can read. Lets say you read off the 20/200 line. A person with emmetropic vision (20/20) could see the 20/200 line at 200 feet, versus your 20 feet.
On to your question.. Near point acuities are also written in Snellen notation (20/X), and are done with a card that has to be held a certain distance from the eye (usually 14 inches). No matter what the testing distance, the vision will still be recorded as 20/X, since it is the most conventional way to see va's recorded.
Why do we record it as 20/20 even though its not at 20 feet?--just because its easier for us to comprehend and thats the way we've done it for years.
You can translate 14/y to 20/x mathematically if you wanna do it the hard way, but its conveniently printed on the card in Snellen notation.
Good job to your son for reading off the small line! Young eyes can accomodate so easily, now when you hit 40, it can be challenging.
The most commonly used format for recording VA's (visual acuities) is in Snellen notation, whether it be for distance or near testing. Snellen notation is recorded as 20/X, where 20 means test distance, and X is the line of acuity the patient can read. Lets say you read off the 20/200 line. A person with emmetropic vision (20/20) could see the 20/200 line at 200 feet, versus your 20 feet.
On to your question.. Near point acuities are also written in Snellen notation (20/X), and are done with a card that has to be held a certain distance from the eye (usually 14 inches). No matter what the testing distance, the vision will still be recorded as 20/X, since it is the most conventional way to see va's recorded.
Why do we record it as 20/20 even though its not at 20 feet?--just because its easier for us to comprehend and thats the way we've done it for years.
You can translate 14/y to 20/x mathematically if you wanna do it the hard way, but its conveniently printed on the card in Snellen notation.
Good job to your son for reading off the small line! Young eyes can accomodate so easily, now when you hit 40, it can be challenging.
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Originally Posted by jamesk,Nov 20 2006, 07:10 AM
Hey guys, I'm an ophthalmic tech so I thought I'd chime in.
The most commonly used format for recording VA's (visual acuities) is in Snellen notation, whether it be for distance or near testing. Snellen notation is recorded as 20/X, where 20 means test distance, and X is the line of acuity the patient can read. Lets say you read off the 20/200 line. A person with emmetropic vision (20/20) could see the 20/200 line at 200 feet, versus your 20 feet.
On to your question.. Near point acuities are also written in Snellen notation (20/X), and are done with a card that has to be held a certain distance from the eye (usually 14 inches). No matter what the testing distance, the vision will still be recorded as 20/X, since it is the most conventional way to see va's recorded.
Why do we record it as 20/20 even though its not at 20 feet?--just because its easier for us to comprehend and thats the way we've done it for years.
You can translate 14/y to 20/x mathematically if you wanna do it the hard way, but its conveniently printed on the card in Snellen notation.
Good job to your son for reading off the small line! Young eyes can accomodate so easily, now when you hit 40, it can be challenging.
The most commonly used format for recording VA's (visual acuities) is in Snellen notation, whether it be for distance or near testing. Snellen notation is recorded as 20/X, where 20 means test distance, and X is the line of acuity the patient can read. Lets say you read off the 20/200 line. A person with emmetropic vision (20/20) could see the 20/200 line at 200 feet, versus your 20 feet.
On to your question.. Near point acuities are also written in Snellen notation (20/X), and are done with a card that has to be held a certain distance from the eye (usually 14 inches). No matter what the testing distance, the vision will still be recorded as 20/X, since it is the most conventional way to see va's recorded.
Why do we record it as 20/20 even though its not at 20 feet?--just because its easier for us to comprehend and thats the way we've done it for years.
You can translate 14/y to 20/x mathematically if you wanna do it the hard way, but its conveniently printed on the card in Snellen notation.
Good job to your son for reading off the small line! Young eyes can accomodate so easily, now when you hit 40, it can be challenging.
I still note a person's vision to be at 20/xx with a near card but there's also a Jaeger or point notation.
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While we're on this near vision thing, my Dr. says that it's difficult for eyes to adjust to contacts for up close vision. Have you guys found this to be true? I can read up close stuff better without my contacts than with them on.
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