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Registered: 05-2005
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less than 2% of people can see 20/10 its very rare!


I'm amused by all the 20-this and 20-that stuff.


For one thing, there is no such thing as 20/5. In 25 years of practive.
I'v never seen a chart with that level of resolution. Know why? Because
the human vision system is incapable of resolving that size of image.
So much for the 20/5 post.


Now onto 20/10. Again, so rare as to not be routinely tested. Less
than 2 % of the human population has the ability to resolve that size
image. Know why? Because it requires that the cone receptor density in
the fovea centralis exceed the normal genetically determined mass. Also
requires perfect optics in all the ocular media---perfect cornea and
lens without artifacts and perfectly clear liquid media without Tyndel
effect. In simple terms, 20/10 is a genetic fluke. Sure seems like a
lot of LASIK'd people get it, though. (In real-life, when refractive
mapping-linked scanning laser gets perfected, it IS possible that
"adaptive optics" may bring the resolving power close to 20/13 and allow
those genetically superior people with 20/10 potential to achieve that
level of optics. But do you really want to see the weave in the material
of your shirt sleeves or the microfine wrinkles in your skin??)


And finally, the optimized acuity depends on contrast sensitivity and
off-axis abberations. LASIK'd vision systems have decreased contrast
sensitivity and sometimes significant off-axis abberations---especially
noticable in reduced lighting due to larger pupil size. So just because
one can read some (or all) letters on the 20/15 line with projector
contrast/brightness optimized but with a little haze and ghosting does
not mean that that 20/15 is the same resolution as 20/15 achieved based
on a "normal" cornea under reduced contrast without abberations.


And you know what? None of this really matters in real life anyway. If
you can see as clearly as your lifestyle demands, it doesn't matter what
the numbers say. My vision (wthout correction) is around 20/25 due to a
bit of astigmatism, better than 20/20 with my pupil stopped down in
sunlight and for me, that's just fine.


I have patients that specifically ask that their correction NOT be
optimized for maximum distance acuity. I'm fine with that.


Somethings are better left unseen. And unsaid.


--Larry


(PS: For those readers who use metric (most of the world), Snellen
acuity can be converted by dividing each number by 3.3, so 20/20 = 6/6)


--
Larry Bickford, OD
Doctor of Optometry, Family Practice Eye Health and Vision Care


1/3/2006, 3:42 am Link to this post Send Email to Myope5   Send PM to Myope5
 
Myope5 Profile
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Re: less than 2% of people can see 20/10 its very rare!


To add, many optometrists dont know how to properly determine one's BCVA.

http://com5.runboard.com/bwelcometothevisionandeyeforums.fmyopescorner.t36


Read the above thread. Truth is 20/10 is very rare. To qualify, you need to see more than 2/3 of the time correct and better yet, 4/5 which happens to be the standard minimum to be a pilot. This means you gotta get at least 4 out of 5 on the 20/20 line. Theres a number of 20/15 people that can "see" or rather, guess 1 or 2 on the 20/10 line.
1/3/2006, 3:57 am Link to this post Send Email to Myope5   Send PM to Myope5
 
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Re: less than 2% of people can see 20/10 its very rare!


This is what one optometrist said elsewhere:

Now onto 20/10. Again, so rare as to not be routinely tested. Less
than 2 % of the human population has the ability to resolve that size
image. Know why? Because it requires that the cone receptor density in
the fovea centralis exceed the normal genetically determined mass. Also
requires perfect optics in all the ocular media---perfect cornea and
lens without artifacts and perfectly clear liquid media without Tyndel
effect. In simple terms, 20/10 is a genetic fluke.


My comments: I read that vision up to 20/3 is possible in theory in humans but I doubt any human in the world has that. The normal human retina is capable of anywhere from 20/7 to 20/10 vision and thats if you do away with every imperfectation. You must have perfect optics, lens, cornea, eyeball, everything in order to reach the limit of your retina itself. It would take a genetic fluke to be born with vitrually no imperfectations and another genetic fluke to have a retina with an abnormally high density of rods+cones. I think the world record is like 20/4 and only a handful in the world have 20/5 vision.


"shouldn't all people who have a refractive status greater than 0 be able to see greater than 20/20?"


Only the best what their eyes, optics and retina is capable of. This is called their BCVA because after you correct all refractive error, this is your best corrected vision. Alot of people dont correct to 20/20.


"but the overwhelming majority of my friends (13-14 year olds) see JUST 20/20."


This is very good, its "normal" vision and usually a plano or slightly positive refractive state. Also means a normal retina and good optics.


"I see 20\12 in my left eye. Any lense make the image worse but I can see normal (down to 20\20) with -2 or +1.25.
 
I see better with minus than pluss."


Thats because you can accomodate the overcorrection a minus lens gives. A plus lens would make you in effect, myopic and things up close clear(this is the purpose of reading glasses) but distance will suffer slightly with a weak plus, more with a stronger plus.


"I think I read somewhere that it is because most people have small amounts of astigmatism. My friend (who sees 20/15 to 20/10) just does not have as much astigmatism at my other friends"


Astigmastim is common, but if its the regular kind, it can be corrected. Usually, it makes no difference if your astigmastim is so small such as -.25 or -.5 diopters.


"Even if you removed all traces of hyeropia, myopia, or astigmatism, almost every person's eyes will have a slightly different potential for maximum visual acuity.
 
This is because of the density of "rods" and "cones" on the retina."


Not only that, but high order aberrations which are slight imperfectations on the cornea and lens. Those with more than average amounts of aberrations like me cant correct to even 20/20 while those with very little aberrations can correct better than 20/20.
4/8/2006, 10:34 pm Link to this post Send Email to Myope5   Send PM to Myope5
 
Ihave2010 Profile
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Re: less than 2% of people can see 20/10 its very rare!


Gentlmen,
I'm going to strongly disagree with you. I was just tested yesterday. I'm a 40 year old male and have never worn glasses. I haven't had my eyes tested in 20 years, because I didn't need to. I always thought I saw in super HD and wanted to find out how good my eyes are. The optometrist wanted to stop when I blew through the 20/20 line and I insisted we go as low as he had. I breezed through the 20/15 and 20/10 lines, getting all 5 correct on both lines with no guessing. The only reason we didn't go lower still is that he didn't have a chart for it.
7/6/2016, 10:34 am Link to this post Send Email to Ihave2010   Send PM to Ihave2010 Blog
 
lyons85 Profile
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Re: less than 2% of people can see 20/10 its very rare!


+1 I've always known that I have exceptional vision. I took an eye exam as a kid and was told that I had 20/10 vision in both of my eyes. However I know I can see so much clearer than that, the 20/10 line was perfectly clear, the text could have been significantly smaller and I would have had no problem reading it.

I understand that this is a genetic fluke at best as i read in the dark up close and starred at the sun when I was younger. also my dad is quite severely short slighted, my mum has never needed glasses and has good eyes at 57 however not anything like i was gifted with.

i really want to know if this is a result of a combination of genes or perhaps a mutation?
12/17/2016, 1:59 am Link to this post Send Email to lyons85   Send PM to lyons85 Blog
 


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