Instructions for self vision test:
Vision testing should be performed on each eye separately, wearing distance eyeglasses if required. There are six lines on the screen, you should note the last line number in which you can read most (50-75%) of the letters.
The middle letter of the top line is equivalent to 20/200. A person unable to read this letter with best eyeglass correction is considered legally blind.
The "T" and the "B" on the top line are equivalent to 20/100. 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 third line is equivalent to 20/40, it is the "driver's test" line. You must be able to read most of the letters on this line in order to obtain an unrestricted drivers license in most states including Massachusetts.
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 you are able to read the bottom line, you are probably a good guesser.
This vision test can only be considered a screening test. A variety of factors such as lighting, glare, monitor quality may have an effect on the results of this test.