Nature intended the human eye to read the last line of this card at a distance of ten feet. This conclusion is not a guess, but is based upon the examination of thousands of eyes. In making the test, the number of feet the eye ought to see is written as the denominator of the fraction; the distance the eye can see clearly is the numerator. If the child's card reads, "Right eye 10/10, left eye 10/20," it means that the right eye sees without conscious strain the distance it is intended to see, while the left eye must be within ten feet to see what it ought to see twenty feet away.

The practical steps for a teacher to take in making eye tests are:

1. Scrutinize the faces for a strained or worried expression while reading or writing, for squint eyes, for unnatural positions, and for improper distances (more or less than nine inches) from eye to book.

2. Select for first tests the children who obviously need attention and will be obviously benefited. Use the eye test to help trace the cause of headaches, nervousness, inattention.

3. Let the children mark off the distances with a foot rule and chalk, going as high as twenty. Be sure to get the best light in the room.

4. Start all children on the ten-foot line. If a child cannot read at ten feet the letter which should be seen at that distance, move the child forward, have it step forward and backward, and note the result carefully. It is better to have ten separate letters of exactly the right size and the same size than a row of letters on one card, as in the Snellen test, otherwise memory will aid the eye, or, as happened recently, a whole class may agree to feign remarkable nearsightedness or farsightedness by confusing letters learned in advance from the card. If the Snellen card is used, and if it is more convenient to have both child and card stationary, satisfactory results will be obtained by having the child read from large letters down as far as he can see.

5. Have the child read from right to left, from left to right, or skip about so that memory cannot aid the eye.

6. Test each eye separately. I was twenty-five years old before I learned that my left eye did practically all of the close sight work. A grown woman discovered just a few days ago that she was almost blind in the left eye; when she rubbed the right one while reading she was shocked to find that she could see nothing with the left eye.

7. If the card is stationary and the child moved, and if only one size of the letter is used, put in the denominator the number of feet at which the normal eye should see clearly, and in the numerator the distance at which each eye and both together can easily see. If the regular Snellen card is used containing letters of different size, place in the denominator the number of the lowest line each eye and both eyes together can read easily, and in the numerator the number of feet from card to eye.

8. Explain the result to the child, to his fellows, to his parents. If the left eye reads 10/20 and the right eye 10/30, it means that neither eye is normal, and that reading small type is a constant strain, even though unnoticed. The right eye must be within ten feet to read what it should read at twenty feet. The left eye must be within ten feet to read what it should read at thirty feet. If the two eyes read at ten, it means that in working together they successfully strain for a result that is not worth what it is costing. When eyes thus unconsciously see what they are not intended to see, it is only a matter of time when stomach and nervous system will announce that the strain can no longer be borne. Indigestion, dislike of study, restlessness follow. If, however, the eyes are so near the normal that their story reads 12/10 or 8/10, the strain will be negligible for the present. If, on the other hand, the only difficulty is a confusion of x and z with c and g, it means that there is a strain due to astigmatism, and that the child should be sent to an oculist.

9. Teach children and parents (and practice what you preach) the urgent importance of periodic reexamination, just as you would teach them to visit a dentist twice a year. This is needed by those who wear eyeglasses, and more particularly by those who have recently put them on. Moreover, as shown below, it is needed by children able to pass satisfactorily the Snellen test.

10. Acquire the habit of reading the eye for evidence of temperate or intemperate living, sleeping, eating, dancing, drinking, and smoking. Inflamed eyes are results,—signals of danger. "The organ may be faultless in construction and in its work poor, because of nerve exhaustion, or, in a less and more easily recoverable degree, nerve fatigue." If unusual eye conditions are not readily explained by mode of living or by eye tests, an oculist should be consulted.