20/20 Vision
20/20 vision means perfect vision, right? Wrong! The term actually
signifies "normal" human vision.
Meaning of 20/20 Vision
< http://www.visionww.org/article-what-is-20-20-vision.htm >
"20/20 vision is a term used to express normal visual acuity (the
clarity or sharpness of vision) measured at a distance of 20 feet.
If you have 20/20 vision, you can see clearly at 20 feet what should
normally be seen at that distance. If you have 20/100 vision, it
means that you must be as close as 20 feet to see what a person with
normal vision can see at 100 feet."
Wikipedia article on "Visual acuity"
< http://en.wikipedia.org/wiki/Visual_acuity >
"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."
A Snellen Chart is often used in doctors' surgeries to determine
visual acuity. If you're at work and want to make a dork of
yourself, use the following chart to estimate your visual acuity:
< http://www.mdsupport.org/snellen.html >
Read the instructions to work out how far to stand from your monitor,
and remember to test one eye at a time.
(It turns out that my right eye is better than my left eye.)
