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#1
Old 11-29-2006, 07:51 PM
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Wearing glasses for better than 20/20 vision

Is it true that modern optometry can produce lenses that will give a person with 20/20 vision 10/20 vision, and is this really the equivalent of seeing details that you previously saw at 20 feet away, at 10 feet away?

That almost sounds worth it! (Do they come in contacts?)
#2
Old 11-29-2006, 08:28 PM
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I have no idea but I think you mean 20/10 vision.
#3
Old 11-29-2006, 08:43 PM
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Quote:
Originally Posted by alterego
Is it true that modern optometry can produce lenses that will give a person with 20/20 vision 10/20 vision, and is this really the equivalent of seeing details that you previously saw at 20 feet away, at 10 feet away?

That almost sounds worth it! (Do they come in contacts?)
Sure. You can wear opera glasses. But the magnification that improves your distant vision beyond 20/20 will reduce your peripheral vision, reduce your near vision, and mess up your ability to estimate distances.
#4
Old 11-29-2006, 08:45 PM
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I've wondered, what does 20/20 vision mean anyway, that you can focus to infinity, or what? Is that what they aim for with glasses for myopia? That seems to be what they do with mine.
#5
Old 11-29-2006, 08:50 PM
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My eye sight is better than 20/20 when I'm wearing contacts or glasses. But then, some people can't get corrected to even 20/20.
#6
Old 11-29-2006, 08:51 PM
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Quote:
Originally Posted by riker1384
I've wondered, what does 20/20 vision mean anyway, that you can focus to infinity, or what? Is that what they aim for with glasses for myopia? That seems to be what they do with mine.
It's a comparison ratio. Basically, it's stating that how objects appear to you at 20 feet is how objects appear to "normal" people at 20 feet; i.e., your vision is normal.

In my case, my uncorrected vision is 20/200; objects 20 feet away appear as objects 200 feet away appear to normal people.

(Actually I think it's worse now. To read a book without glasses, I have to hold it about 10 inches from my face.)
#7
Old 11-29-2006, 08:52 PM
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Visual Acuity:

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It is possible to have vision superior to 20/20: the maximum acuity of the human eye without visual aids (such as binoculars) is generally thought to be around 20/10 (6/3). Recent developments in optometry have resulted in corrective lenses conferring upon the wearer a vision of up to 20/10. Some birds, such as hawks, are believed to have an acuity of around 20/2, which is much better than human eyesight.
#8
Old 11-29-2006, 09:40 PM
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Originally Posted by Patty O'Furniture
I created this thread after reading that information on Wikipedia. I came for the Dope
#9
Old 11-29-2006, 09:57 PM
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I have 20/10 vision now in both eyes, thanks to my laser eye surgery. If that counts.

As I understand it, not everyone can be corrected to that level - part of it depends on just how well you eye naturally works. That is, there's more to it than just the focus of the lens. Some people, even with perfect focusing, may only get 20/20 vision, or, presumably, worse.
#10
Old 11-29-2006, 10:02 PM
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I didn't phrase that right, as I know how acuity works, but I'm wondering if normal people can focus all the way out to infinity. Sometimes I get a new pair of glasses and it feels like I'm looking through binoculars, and I wonder if it's actually normal to see out that much.
#11
Old 11-29-2006, 11:21 PM
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My corrected vision with glasses used to be 20/16, i.e., better than "perfect" vision. (Alas, no longer.) Bear in mind that we're talking about averages. So, to say I had 20/16 vision meant that I could see at twenty feet (corrected) what most people only could see (uncorrected) at sixteen. Why? Presumably because my retina were a little more detailed than most. At least, that's how it was explained to me.
#12
Old 11-29-2006, 11:48 PM
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Quote:
Originally Posted by Smeghead
Some people, even with perfect focusing, may only get 20/20 vision, or, presumably, worse.
I don't have a serious problem (can't remember the numbers, but need glasses to drive, but even with brand new glasses I am not 20/20. I have never been (at least since my first test at age 7).
#13
Old 11-30-2006, 09:30 AM
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Keep in mind 20/20 isn't "perfect vision" - after all, what's perfect? Seeing down into the IR or up into the UV? Minute details from hundreds of meters? The 20/20 is just "normal."

So, anyone have scoop on how 20/20 was declared normal? Is it just the median for some specific population, or was there something more involved in its development?
#14
Old 11-30-2006, 09:41 AM
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Quote:
Originally Posted by riker1384
I didn't phrase that right, as I know how acuity works, but I'm wondering if normal people can focus all the way out to infinity.
Seems logical to me that there's a maximum possible resolution discernable by the individual human eye. The retina is, after all, made up of a discrete number of cells ... that would seem to be a limiting factor right there. Focusing "out to infinity" would therefore seem to be an impossibility.
#15
Old 11-30-2006, 10:39 AM
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Quote:
I didn't phrase that right, as I know how acuity works, but I'm wondering if normal people can focus all the way out to infinity. Sometimes I get a new pair of glasses and it feels like I'm looking through binoculars, and I wonder if it's actually normal to see out that much.
"normal" relaxed vision is supposed to be able to see "infinitely distant" objects. So, yeah, normal people can "focus all the way out to infinity". It's focusing closer that takes effort, adjusting the crystalline lens for fine tuning of the focus ability of the eye.

The problem with myopic people like me is that we can only focus out to a nearby distance. We use eyeglasses or contact lenses to shift that "far point" to infinity, so we can see like normal folks.



As for the question in the OP, "normal vision" isn't perfect -- there are aberrations in a "normal" lens, and scattering from the organic elements in the eye, and the like, so that "20/20" vision isn't perfect, and some people will have better than "normal" vision. Presumably, if you had an eye free of most other defects except myopia, with glasses you could see better than 20/20. But someone else whose eyes were as limited as everyone else's, using similar or the same glasses, wouldn't be able to do better than 20/20, and there's no magic set of glasses that would make them see better (without going to something radically different, like binoculars or something, with all its inherent limitations)
#16
Old 11-30-2006, 10:44 AM
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I had been told somewhere in the far distant past that 20/20 vision meant that at a distance of 20 feet you could read a line of text 20 cm high. Is this the correct explanation?

If so, I'm surprised at the mixing of English/metric units to comprise a "standard."
#17
Old 11-30-2006, 10:50 AM
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Quote:
Originally Posted by CalMeacham
As for the question in the OP, "normal vision" isn't perfect
Thanks for the replies! But erm, how does this address the OP? I never said normal, or perfect!

I think the answer is "Yes, Yes, Yes."
#18
Old 11-30-2006, 01:05 PM
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As has been posted, 20/20 is accepted as normal, but many folks, especially youngsters see better than that. I have met an 8 year old that could accuratly discribe the configuration of the Jovian moons from nakid-eye observations.

Until I was 20 or so I had much better than 20/20 vision...the bottom line on a standard eyechart was no problem. At that point, distant signs started to become fuzzy around the edges of the letters. I went to an optomitrist, who rated my vision at 20/15, and advised I not get glasses. A year or so later, I opted for glasses, even though my uncorrected vision still tested at 20/20. Things just didn't look "sharp" without the glasses.
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