The Myth of 20/20
"More than 20 percent of kids aged 12 to 17 have trouble seeing the classroom chalkboard, a new national survey shows."
20/20 is a measurement of how clearly you see in the distance (or visual acuity at distance). Visual acuity means sharpness of vision.
If your standard vision test reports 20/20, it means that you are able to see clearly at 20 feet what should normally be seen clearly at 20 feet. On the other hand, if you have 20/40 vision, it means that you need to stand as close as 20 feet to see what a person with normal vision can see clearly at 40 feet.
20/20 does not mean that vision is perfect!
The 20/20 test does not test how well you see at reading distance. In fact, the 20/20 test fails to evaluate many other important aspects of normal vision such as:
Eye Movement Skills (tracking) - the ability to move the eyes smoothly, accurately and effortlessly in tandem whether following a line of print in a book or the flight of a ball through the air.
Focusing Skills (accommodation) - the ability to look quickly from far to near and vice versa without momentary blur (e.g. looking from the chalkboard to the book). This skill involves the clearing of an image for identification.
Eye Teaming Skills (Binocularity) - the ability to use both eyes together smoothly, equally, simultaneously, and accurately. All judgments of spatial localization, depth perception and the accuracy of a single clear image depend upon this paired action of the eyes.
Eye-Hand Coordination Skills (visual motor integration) - This ability is dependent upon the use, practice and integration of the eyes and the hands as paired learning tools. With this skill comes more effective ability to make visual discrimination of size, shape, texture and location of objects.