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Medical Forum / General / Vision / November 200620/5 is the theoratical limit of the retina! We have the potential of a hawk!
The theoretical limits of God's masterpiece is a retinal 20/5. We have the same rod and cone density as a hawk. We just don't have the same optics. *the above is what one expert said. Very interesting tibit! This shows that optical imperfections, astigmatism and high order aberrations results in most humans having a BCVA of 20/15 to 20/30(mine is 20/25 and 20/30) I did read that a healthy human retina should have a potential of at least 20/8 to 20/10 and in fact over 99% of human retinas are capable of 20/10 or better. But because of optical limitations, 20/10 with or without glasses/contacts(non wavefront) is rare, encomposing between 1% and 2% of people. Sorry but straining to pump out a couple 20/10 letters doesnt count. I have gotten a couple 20/20 letters before by straining but my BCVA isnt true 20/20(due to complex astigmatism and HOAs) Nice Analysis, Ace. The practical value was established by a number of people, notably Snellen, Helmholtz, Donders and others. By practical testing (and use of the minus lens) they determined that most retinas could resolve 1 minute-of-arc. Snellen, converted this to a chart with 5 minute-of-arc letters -- which has become the "world" standard for visual-acuity testing. Finally, the Army (about 1914), gave up on naked-eye visual acuity of 20/20, and to avoid the use of a "lens", which might produce a "flash" in sunlight, determined to make the visual-acuity requirement 20/40 in the better eye, or 20/40 with both eyes open. In fact that is probably how the DMV requirement came about. The people who have better-than 20/20 tend to be baseball players and other "out-door" types. 20/15 in indeed superior, with some to about 20/12 and even 20/10. But that is rare. As always, most ODs will prescribed for "Best Visual Acuity", which means that the person will get the sharpest vision possible from the minus lens prescribed. Best, Otis > The theoretical limits of God's masterpiece is a retinal 20/5. We have > the [quoted text clipped - 12 lines] > 20/20 letters before by straining but my BCVA isnt true 20/20(due to > complex astigmatism and HOAs) Nothing like a retard and his mentor to solve the world's ills for all. > We have the same rod and cone density as a hawk. We just don't have the same > optics. Hawks have a protrusion in the middle of their retina that makes their cone density effectively higher than ours. LD > > We have the same rod and cone density as a hawk. We just don't have the same > > optics. [quoted text clipped - 3 lines] > > LD what im thinking is while both humans and hawks have retinas capable of 20/5, hawks have their retina set up to be more effecient, such as a central protrusion. Humans have a fovea and perhaps that part of the retina is capable of 20/5 while hawks have a larger part of the retina capable of 20/5. Humans have much more aberrations than hawks so its rare for humans to see better than 20/15. If we removed all aberrations and other optical imperfections, would they still see as well as a hawk or at least nearly so? Ive heard the 20/8 figure thrown alot as the retinal limit of the average human I think that we have also some advantages over Hawks. Hawk = predator? --> bad peripheral vision, good distance vision man = prey? --> better peripheral vision, not so good distance vision Our peripheral vision is better than that of the hawk. So that we can see predators from the angle of our eye and run away. Typically men have more of the predator type eye. And women more of the prey-type eye. Does not mean that men hunt women. But means that women like to be hunted (??). I guess that's why we don't get along. > I think that we have also some advantages over Hawks. > [quoted text clipped - 6 lines] > eye. Does not mean that men hunt women. But means that women like to be > hunted (??). I guess that's why we don't get along. LOL this makes no sense. Humans are predators and have no natural enemies unless they are doing something really stupid like being at a place they shouldnt be such as swimming with shaks and aligators or playing with snakes and lions. We dont have the peripheral vision that pray like mice and rabits do. >> I think that we have also some advantages over Hawks. >> [quoted text clipped - 6 lines] >> eye. Does not mean that men hunt women. But means that women like to be >> hunted (??). I guess that's why we don't get along. Probably has to do with women being able to multi-task way than men. Grub the roots, keep your eye on the kids, and don't forget to watch out for the sabre-tooth hiding in the rocks. > LOL this makes no sense. Humans are predators and have no natural > enemies unless they are doing something really stupid like being at a > place they shouldnt be such as swimming with shaks and aligators or > playing with snakes and lions. We dont have the peripheral vision that > pray like mice and rabits do. Underneath all the sophisticated trappings of civilization, we're still stone-age people. I would think that having a lion or tiger sneak up on you would have definitely been a problem at the time, and those who didn't notice probably didn't pass on many of their genes.  SignatureCheers, Bev ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ (On going to war over religion:) "You're basically killing each other to see who's got the better imaginary friend." -- Rich Jeni |
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