20/20 is perfect vision!
Yep......
barry
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20/20 is perfect vision!
Yep......
barry
Actually I think 20/20 origionally ment that you could resolve the same images and angles (such as E's) as the average marksman in the Crimean War on the British side as measured by Hemholtz.
Mearly this and nothing more. Some such marksmen saw better than others as all of you know marksmanship has to do with the abilities to estimate the wind, hold the rifle, estimate light, movement, bullet drop, powder load, bullet weight, rain, and a lot of factors as well as sight. Most marksmen (despite being taught to use two) shoot with only one eye, so theoreticly, only the va in the shooting eye would be of importance. If they were all missing the non-shooting eye, it would be irrelevant to the study but it sure would skew the statistics.
Some would see better or worse that average at 20' but would have some better compensation of the other relevent things to thier shooting skills, especially since these were battlefield marksmen and not target range marksmen.:cheers:
Chip
There's some days I wish I could give the full moon patients my 20/20 :p
Ever since I was a "puptician" it was my understanding that 20/20 is not perfect vision, but is normal vision and is further defined as an individual being able to see an object that subtends a 5 degree angle at a distance of 20 feet.
Perfect vision is as yet undefined but the individual sustains great shock and awe when seeing an object that subtends a 5 degree angle at greater distances than 20 feet, thereby making blind idiots of all his friends except his mother who wanted him to be a doctor!
Sorta right, it's 5 minutes of arc which is the equivalent of 1/12th of a degree, I made that mitake once myself.Quote:
Originally Posted by Alan W
Visual acuity is ultimately limited by the aberrations of the eye, diffraction, and the density of the photoreceptors of the retina. You are unlikely to ever see visual acuities below 20/12 or 20/15.
Darrell:
A very high percentage of rigid contact lens (especially PMMA) wearers can see 20/10. I have over the years even had to two that could read the fine print at the bottom of the chart telling where it was printed.
Had a 10 diopter myope Friday in RGP's see 20/15 + in a poorly lit room with an unilluminated wall chart.
Chip
I don't discount the possibility, particularly with a chart at maximum contrast, absence of significant higher-order ocular aberrations, narrow pupil size, etcetera; but I do discount the likelihood. If you indeed have a "significant" percentage achieving 20/10 visual acuity, which is often quoted as the diffraction limit for a 2 or 3 mm pupil, I would start marketing yourself as a "supervision" provider in your area to compete with those ophthalmologists using wavefront-guided LASIK. ;)Quote:
A very high percentage of rigid contact lens (especially PMMA) wearers can see 20/10. I have over the years even had to two that could read the fine print at the bottom of the chart telling where it was printed.
Yeh, thats the ticket!
Like I said . . . it's been since I was a puptician!
Thanks.
20/10 is under 1%, but I agree that RGPs give you a fightin' chance.
Usually it's some 20-50 y.o. male, in my opinion, that's +0.25.
I'd say it's closer to 10+ percent if one is concentious enough to refract over the contacts and change as needed. This is part of what's called "fitting" as opposed to "filling the Rx."
I have patients with 4 or more diopters of cylinder and 20/10 with contacts. Even have a lot with bifocals (not the norm though) that see 20/10 J-1. What's the big deal. Also note not many of my patients are healthy teenage myopes like they used to be. Seldom did I fail to get at least one line better than spectacles when they were.
Of course this is undilated acuity.
Chip
"I think the lexical confusion arises... "