how many lines on an eye chart
The second line is 20/50. Best corrected acuity in the range between 20/50 and 20/100 is considered disabling in occupations which require work with numbers or extensive reading. The bottom three lines represent 20/30, 20/20 and 20/10. These are considered to be normal vision with the 20/20 line being the traditional normal vision line. It is generally felt that the maximum visual acuity of the eye is around 20/15 or 20/16. This means that if the customer is able to read the bottom line, he/she is probably a good guesser.