The first twenty in the term “20/20” is how many feet you are from the eye chart. In most eye doctor offices that eye chart is 20 feet away from you. The second twenty is the size of the lettering. So 20/20 means that the average (see, there’s that word again) person should be able to see a 20-size letter from 20 feet away. What if you have horrible vision – 20/200? That means that the letter your able to barely make out sitting in the exam chair has to be 10 times (200 is 10 times larger than the 20-size letter) larger for you to tell what letter it is (see figure 1).
The goal of most eye doctors is to correct your vision to only 20/20. However, this is quickly becoming an old standard. In prior years we could only correct four eye problems with conventional glasses – nearsightedness, farsightedness, astigmatism, and prism. These are called low-order aberrations. This left smaller visual distortions uncorrected, called high-order aberrations. It’s these distortions that result in “fuzzy” vision. This is why some patients can still read the 20/20 line, but the vision is still “off” (see figure 2 – left side). Additionally, you may see halos, glare, or starbursts around lights at night if you have these distortions.