by William H. Bates, M. D. Д. БейтсReprinted from New York Medical Journal, July 29, 1911, vol 24, no 5, pp. 237-238.
THE PREVENTION OF MYOPIA IN SCHOOL CHILDREN.
By W. H. BATES, M.D.
In 1903 I examined the eyes of 1,500 school children at Grand Forks, N.D., a city of 12,000 inhabitants, and found six per cent. myopic. The superintendent, Mr. J. Nelson Kelly, was interested in the facts and desired prevention. At my suggestion Snellen test cards were placed in all the class rooms with directions for their use. The results were so encouraging that the method was employed continuously for eight years and is still in use. In 1910, among 2,000 children, less than one per cent. were myopic.
The children were examined during a study period while sitting in their seats.
After testing the sight of all the children in one class coon the teacher asked me the character of the vision of one of the boys. I said his sight was normal—that he was slow in reading the letters of the test card; but, after some encouragement he read the smallest letters the normal eye should see at his distance from the card. The teacher was incredulous and told me very emphatically that she was positive the boy was "near sighted." She declared his vision for all distant objects was poor: he was unable to read the writing or figures on the blackboard, he did not recognize people at a distance, or see the maps, charts, or diagrams on the walls. The teacher told me that my conclusion was erroneous. She suggested that the boy might have learned the letters or had been prompted by another pupil. She asked one to test him again. The second examination was made carefully under her supervision, the sources of error she suggested were met, and I found the boy's sight was normal. Immediately afterward the teacher tested his sight with the writing on the blackboard and the boy read what she had written. Then she wrote additional words and figures which the boy read equally well. She asked him to tell the hour by a clock twenty-five feet distant which he read correctly. It was a dramatic situation. The children were intensely interested. I was impressed by her surprise when she was convinced that the boy's vision was normal.
Three other cases in this class were similar and on examination yielded identical results. The teacher asked for an explanation. I told her that when the children looked at the blackboard or other distant objects and strained or made an effort to see better, they focussed their eyes for a near point and consequently could not see distant objects clearly; and, while testing the vision with the Snellen test card, I educated them to use their eyes properly for distant vision. It was interesting also to me to find that the few moments devoted to testing them were sufficient to relieve these children so that their vision for distant objects became normal. This teacher at once realized that the Snellen test card was valuable in relieving and preventing defective vision. At her request a Snellen card was given her which was placed permanently on the wall of the class room where all the children could see it from their seats.
NORMAL EYES WITH DEFECTIVE VISION FOR DISTANCE.
This fact was demonstrated as follows: The child regarded objects ten feet, twenty feet or more distant. When the distant object was a Snellen card at ten feet and while the child vas reading the line marked 10, or had normal vision, the retinoscope, used simultaneously, showed no myopia. But when the child regarded at ten feet or further, a picture, a map, the writing on the blackboard, a person, a book, or some other object with which he was not familiar, the retinoscope used simultaneously indicated near focus of one or all meridians, functional myopia, or myopic astigmatism. A positive result, near focus of the eye, was always observed when the child made an effort to see distant objects.
No special drill was requisite to make this demonstration. During the past year 100 persons, not physicians, demonstrated with the aid of the retinoscope that all school children did not adjust their eyes accurately for distant vision. Children, ten years old, handled the retinoscope successfully and told me promptly when near focus of the eye occurred. The matter is so important that I strongly recommend all physicians, teachers, and others, interested in the welfare of the eyes of school children and in the preservation of their own vision, to obtain a retinoscope and learn by a practical demonstration that all school children and many adults do not usually adjust their eyes accurately for distant vision. By doing this one obtains a grasp of the subject which Will be of material benefit. A retinoscope with instructions will be sent free to any one on request.
Why was the Snellen test card better than other distant objects to improve the sight? It enabled the pupil to know when an improper strain or effort to see was made. It was only when the eyes were property adjusted for distant vision that the small letters were read. With other distant objects children had greater difficulty in knowing when the focus was adjusted accurately. Many persons with normal eyes believed erroneously that they saw better at the distance by partly closing the eyelids or by otherwise straining the eyes; but, when they looked at the Snellen card, they at once discovered that the effort made the letters indistinct.
Why did children strain their eyes when looking at distant objects? They strained because their experience had taught them that to accomplish most things an effort was required. They had learned that they saw near objects more distinctly by making a voluntary effort. Naturally, most of them strained when looking at distant objects, to improve their sight.
How did straining to see distant objects lessen the vision? We know that distant objects were seen most distinctly by the normal eye when the muscle which controlled the focus was at rest. Any contraction of this muscle which was produced by straining always focussed the eye for a near point and produced functional myopia. When the eye was focussed for a near point, objects at a distance were indistinct.
THE PRINCIPAL FACTOR IN THE CAUSE OF MYOPIA IN SCHOOL CHILDREN.
The normal eye could focus for near and distant objects.
The myopic eye could focus only for near objects. Obviously, the principal difference between the two was in the ability of the normal eye to see at a distance.
When the normal eye acquired myopia it lost the ability to adjust its accommodation for distant vision, therefore: All individuals with normal eyes who do not adjust their accommodation accurately for distant vision become myopic.
Nothing else was possible. It was self evident. The demonstration of temporary functional myopia is simple: Look at the letters of a distant sign and note their clearness. If one has normal eyes any effort or strain made by staring, partly closing the eyelids, or focussing a nearer point, is followed by a blurring of the distant letters, In 1910 I demonstrated this fact with the aid of the Snellen card to 2,000 school children whose ages ranged from six to twenty years.
1. All children did, not focus accurately writing on the blackboard, or pictures, maps, persons, or other new or strange distant objects.
2. They became myopic when they did not learn to adjust their eyes properly for distant vision.
3. Myopia was prevented by teaching school children to focus their eyes accurately for distant objects.
4. The Snellen test card was found to be the best object to use for exercises in distant vision. It was placed permanently in each class room where all the pupils could see it from their seats. They were encouraged to read daily the smallest letters they could see, with each eye separately, covering the other eye with the palm of the hand in such a way as to avoid pressure on the eyeball.
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