Eugene DeVincenzo, age 11, of North Lima, Ohio, for his question:

WHAT DOES 20 20 EYESIGHT MEAN?

Eye doctors use highly sophisticated machines and instruments with many lenses and mirrors to check a person's vision and to make a complete measurement of the need of the eyes for corrective glasses. The doctors also have to make sure there are no hidden abnormalities of eye muscles or that part of the nervous system that is associated with eye movement.
Perhaps the most common eye test used by doctors who check your vision is one that utilizes a poster called an E chart. The chart, which can be of massive wall size or just a hand held card, has the letter E printed in many different sizes and various positions.
Doctors consider the test an excellent one, because it can be given by a nurse or office assistant with little training. It also involves just the one simple character, rather than lots of letters, so even young children or those who are illiterate have few problems in passing on their answers.
The E chart, or the alphabet eye chart, is used in many schools for mass screenings since elaborate equipment is not needed. If a child does not do well on this test, further examinations can be scheduled.
Eye tests are given at different distances but the results are given on the basis of a chart 20 feet from the viewer. A person over the age of 5 years is classed as having normal vision if his rating is 20 20. This means, simply, that the viewer can read a relatively small line of letters (or tell the direction in which the letter E is printed) at 20 feet, which the normal eye should be able to see at that distance. The first number or. the rating is the distance with the second number being the normal  so that a rating of 20 40 means a person can read at 20 feet the letters a normal adult eye should see at 40 feet.
Tests are first made with one eye covered, and then the other. It is possible, therefore, to find that a person has 20 30 vision in the right eye and 20 20 in the left. With this type of situation, a person would probably need eyeglasseswith a magnification lens only for the right eye, with plain glass used for the left.

Improper refraction is the reason many people must wear eyeglasses. If the eyes are not able to refract and focus light properly, it is usually the result of inherited tendencies. One type of improper refraction is called myopia, or nearsightedness. Another is called hyperopia, or farsightedness. If a person has refraction problems with his eyes, chances are it will first be spotted by the doctor who reads the results of an E chart eye test.