The Myth of 20/20eyechart
 
"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.

Symptoms:

  • head turns as reads across page
  • loses place often during reading
  • needs finger or marker to keep place
  • too frequently omits small words
  • displays short attention span in reading or copying
  • writes up or downhill on paper
  • rereads or skips lines unknowingly

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.

Symptoms:

  • tires easily
  • blinks to make the chalkboard clear up after desk work
  • rubs or blinks eyes during or after short periods of visual activity
  • makes errors in copying from chalkboard to paper or desk, or from reference book to notebook
  • avoids near centered visual tasks
  • comprehension reduces as reading is continued
  • loses interest too quickly

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.

Symptoms:

  • squints, closes or covers one eye
  • extreme head tilt while working at desk
  • complains of seeing double (diplopia)
  • omits letters, numbers or phrases
  • repeats letters within words
  • misaligns digits in number columns

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.

Symptoms:

  • writes crookedly, poorly spaced; cannot stay on ruled lines
  • uses finger or hand to keep place on the page
  • must feel things to assist in any interpretation required
  • uses other hand as a "spacer" to control spacing or alignment on the page
  • eyes not used to "steer" head movements
  • extreme lack of orientation in placement of words or drawing on the page