The traditional Snellen chart is printed with eleven lines of block letters. The first line consists of one very large letter, which may be one of several letters, for example E, H, N, or A. Subsequent rows have increasing numbers of letters that decrease in size. A patient taking the test covers one eye and reads aloud the letters of each row, beginning at the top. The smallest row that can be read accurately indicates the patient's visual acuity in that eye.
JAD showed the group that if you can read the bottom row, you have 20/10 vision. He said that Ted Williams, baseball player for the Red Sox, had 20/10 vision.
- the thickness of the lines equals the thickness of the white spaces between lines and the thickness of the gap in the letter "C"
- the height and width of the optotype (letter) is five times the thickness of the line.
Only the ten letters C, D, E, F, L, N, O, P, T, Z are used in the traditional Snellen chart.
Jad brought with him several charts including one that he uses for children. The kids chart showed symbols rather than letters. He even has cards with an E on it so that parents an take them home and have their children practice with it. Sort of like studying for your Eye Tests.
The presentation had one member exclaim:
"Today's meeting was brought to us by the letter E."