What is 20/20 vision?
If you have been told you have 20/20 vision, you have what has been defined as humanity’s “normal” eyesight. You can see clearly at all distances. Those numbers refer to feet from an eye chart.
The typical eye chart has a large “E” at the top and lines of smaller letters underneath. When your eye doctor tests your vision for glasses or contact lenses, you look into a device called a phoropter. You are asked to read the smallest row of letters you can clearly see, and the doctor flips from lens to lens asking you to compare: “Which is clearer, this … or this?”
The phoropter is simulating your distance from the eye chart. In the expression “20/20”, the first number refers to the tested eye’s distance in feet from the chart. The second number changes according to your visual acuity.
- If you have 20/40 eyes, you must be only 20 feet from the chart to see what “normal” eyes can see clearly from 40 feet away. You are mildly nearsighted.
- If you have 20/100 vision, you are more nearsighted, and normal eyes can see at 100 feet what you can only see from 20 feet away
- Legal blindness is defined as 20/200, where the eyes being tested must peer at the letters from 20 feet way to see what “normal” eyes can see from 200 feet away.
“Better Than Normal” Vision
After having a custom LASIK procedure, some people achieve 20/16 vision. That means their visual clarity is better than what is considered normal. In terms of the eye chart, they can see from 20 feet away what a “normal” person must be only 16 feet away to see clearly. These superior results are possible because Wavefront technology is used for diagnosis instead of a phoropter. It gives a more microscopically precise picture of your eye contours, which means your LASIK treatment can be more precise.
Please see our page on How the Eye Works for more detail on eye anatomy and how an eye can be nearsighted, farsighted or astigmatic.
To learn more about what LASIK could do for your vision, and to learn more about your eyes, please contact our office for a free, personal consultation with Dr. Penno.
