Wednesday, November 8

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.)