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Popular Science Monthly/Volume 71/October 1907/The Sacrifice of the Eyes of School Children

< Popular Science Monthly‎ | Volume 71‎ | October 1907


The Human Eye evolved for Distant Vision

By Professor WALTER D. SCOTT


IN the evolution of the animal organism the sense of touch has served the purpose of informing the individual of objects with which it came in contact. The sense of taste likewise gave information concerning objects upon contact, but of a more specialized form. The sense of smell and that of hearing gave knowledge of objects in the vicinity and in certain instances of objects in the distance. The sense of sight seems to have been preeminently the sense by means of which the individual was enabled to adjust himself to objects at a distance. The enemy to the leeward might approach noiselessly and so could not be smelt or heard. When knowledge of the approach was revealed by the sense of touch it was too late for escape. The preservation of the individual and of the species thus depended upon the ability to see the enemy in the distance. Inasmuch as the function of the eyes has been to perceive objects at a distance rather than at close range, we are not at all surprised to find that the eyes are well adapted for distant vision, but poorly constructed for close work.

When our eyes are at perfect rest, when all the muscles which control them are relaxed, they are then adjusted for distant vision. When, on the other hand, the ciliary muscles and the muscles which move the eyeballs are at a maximum of contraction, then and then only are the eyes adjusted for close vision. Such a structure was admirably adapted to the needs of the primitive organism. The eyes were the sentinels which must always be on guard and when employed in the appropriate way there was no strain. It was of course essential that the individual should be able at times to see objects close at hand. This could be accomplished by means of contractions of delicate muscles, and as soon as the contractions were relieved the eyes were again adjusted for the more important duty of distant vision.

The strain upon the eyes is in adjusting for objects closer than at about four feet, but for all greater distances there is a minimum of strain. Hence we may speak of all objects as being distant which are removed as much as four feet. With this definition of the term distant it is evident that distant vision was the most common form of vision for all our ancestors, from the most primitive forms of life to the most highly civilized races, till the last few centuries. With the invention of writing and then with the invention of the printing-press a new element was introduced, and one evidently not provided for by the process of evolution. The human eye which had been evolved for distant vision is being forced to perform a new part, one for which it had not been evolved, and for which it is poorly adapted. The difficulty is being daily augmented. The invention of printing presses has been followed by an increasing number of books, magazines and daily papers. The rural population has given place to the urban. The long days of manual labor have given way to the eight-hour system with abundant time for reading. Labor-saving devices of all sorts have added to our sedentary habits. All things seem to be conspiring to make us use our eyes more and more for the very thing for which they are the most poorly adapted. It requires no prophet to foresee that such a perversion in the use of an organ will surely result in a great sacrifice of energy, if not of health and of general efficiency.


The Amount of Light required for Reading

The eye has thus far been spoken of as though it consisted merely of delicate muscles, when in reality these are not the most significant part of it. In thinking of the eye we should never disregard the eye-muscles, but primarily the eye is a live camera consisting of a lens, dark box and sensitive plate. The retina in the back part of the eyeball is the sensitive plate and is the most vital part of the eye. It is effected by every ray of light falling upon it. Fortunately it responds to a weak light and still is not injured by a moderately strong one. In speaking of the quantity of light it is well to have a standard. For this purpose the most convenient standard is the amount of light cast by a standard candle upon any point in the horizontal direction one foot from the candle. A light of twice this intensity is spoken of as a two-candle power, a light ten times the first is of course a ten-candle power. The light cast by a candle upon a printed page at a distance of one foot is sufficient for legibility at the normal reading distance. If the light is less than this the retina is not adequately stimulated and the reading is accomplished only after a strain more or less intense. If the light falling upon the page exceeds ten-candle power the stimulation of the retina is so great that it is displeasing to some people and is condemned by our best authorities as injurious to the retina. All are agreed that less than a single candle-power is injurious for reading, and during the present state of our knowledge it is at least safe to avoid an illumination of more than ten-candle power.

The iris may be blue, brown or gray and is that which determines the color of our eyes. It is an adjustable shutter which reflexly regulates the amount of light which enters the eye. In the presence of a bright light the iris diaphragm contracts, reducing the size of the pupil and cutting out much of the light which would otherwise enter the eye. In the presence of a dull light the pupil enlarges, allowing a great amount of the light, such as that falling upon a book, to enter the eye and to stimulate the retina. The iris is a wonderful device, but can not in diverse illuminations perfectly equalize the amount of light entering the eye. The pupil expands inversely as the square root of the illumination. Thus if the actual illumination of the book increases ten-fold, the amount of light falling upon the retina is increased but little over three-fold. Even a twenty-five candle light sends but five-fold as much light into the eye as a single candle-power. A single candle-power seems sufficient and ten-candle power is not too much. This ability of the retina and of the iris to deal successfully with lights of such different intensities is a most useful and necessary characteristic. Unfortunately, however, the actual diversities of intensities of lights used for reading are far beyond any for which the eye can adapt itself.


Variations in the Amount of Daylight

We are in the habit of thinking of the light received from the sky—the daylight—as almost a fixed quantity during the hours from 9 in the morning till about 4 in the afternoon. The darkness preceding a storm and the occasional dark days are of course not forgotten, but, in general, daylight for the hours mentioned is thought of as at least fairly constant. To test this point observations were made at 9 a.m., 12:30 p.m., and 4:30 p.m., daily for five and one half days a week for 22 months. These tests were made in the Chicago laboratory of the American Luxfer Prism Co., and under direction of Professor Olin H. Basquin, of the Department of Physics of Northwestern University. Inasmuch as the amount of sunshine and general illumination in Chicago is almost exactly the average for the United States, these results may be regarded as typical for the whole country with the exception of such dark cities as Seattle or such light ones as Phcenix, Measurements were made of the amount of light coming through a square foot of clear glass placed horizontally in the roof of the observation building. The illuminometer was placed so far below the opening in the ceiling that the direct rays of the sun could never reach any part of the recording apparatus. The light thus measured was diffuse daylight received from the zenith of the sky. Taking the average illumination for the 22 months at 12:30 as the standard, it was found that the illumination at 9 a.m. was but 67 per cent, as great as that of mid-day. Again the illumination at 4:30 p.m. was but 27 per cent, as great as that at 12:30. Expressed in other terms, we see that the available light at 4:30 is approximately but one fourth that of noon and the light at 9 o'clock but two thirds that of noon. These figures are the average for the school days of 22 months in one city, and although observations for a longer period and in other cities might change the results somewhat, it is safe to assume that our figures are not far from the actual conditions in a majority of our school rooms in the United States. In general a room which is barely adequately lighted at 12:30 will be 33 per cent, under-illuminated at 9 o'clock, and at 4 o'clock its illumination will be but 27 per cent, of the necessary amount.

Our difficulties are further complicated by the fact that the variations in illumination of daylight are as great between the months of the school year as between the hours of the school day. The illumination is best in the months of June, July, August and September. Then follows in order May, April, March, October, February, November, January and lastly December. Comparing the illumination of the four bright months (June, July, August and September) with the four dark months (November, December, January and February) we find that for the 22 months observed the illumination of the dark months is but 28 per cent, of that of the bright ones. This figure is found by averaging the three daily readings for each day for all the months concerned. December, the darkest month has but 18 per cent, as great illumination as June, the brightest month.

When to these variations as between months or seasons we add the variations between mid-day and morning and evening, the results are most astounding. The light at noonday in June averages almost ten-fold as much as that at 9 a.m. in December. If it is injurious to read with a light less than one or more than ten-candle power, a schoolroom that furnishes this maximum in June will be reduced to the minimum in December mornings and evenings on average days. Such deviations in the external source of light put most restricting conditions upon school architecture. How have we met the conditions and how might we construct our schoolrooms to meet the situation satisfactorily?


Rules for Lighting a Schoolroom

In our climate it is almost impossible to over-light a school room if the two following conditions are observed: (1) Never allow the direct rays of the sun to fall upon any surface within the field of vision of any pupil. (2) Avoid all glossy or shiny surfaces which reflect the light directly into the eyes of the pupils. A dead white surface is not injurious, while a darker surface may be shiny and hence injurious.

For securing adequate light the following rules are important: (1) The window space should be as much as one fifth of the total floor space, and the height of the window two thirds of the width of the room. (2) The walls, ceiling, woodwork, furniture, etc., should be a color which reflects a large amount of well-diffused light. Perhaps the best colors for this purpose, in the order of their efficiency, are white, light yellow, light gray, light green, light blue and light pink. (3) The schoolroom should be narrow and the windows facing an unobstructed area, so that from any seat in the room a large amount of sky is visible. (4) The windows should be provided with white Holland screens, or others of a similar sort, which obstruct the direct rays of the sun, but which, when drawn down, emit into the room a maximum of diffused light. (0) There should be at hand light colored curtains which may be used to cover up all blackboards as soon as the darker parts of the room are inadequately lighted.

It is apparent to all that the construction of our school rooms has not conformed to these five simple rules. There are many rooms in which the window space is one fifth of the floor space, but certainly not a majority of all schoolrooms in America. The second rule, concerning the reflecting surfaces within the schoolroom, is broken by the extensive surfaces of black-boards and by the dingy color of the walls. Walls soon fade and become dirty and need frequent attention to keep their reflecting power approximately at its maximum. The third rule is broken by constructing rooms so large that they will accommodate fifty pupils, and by placing school buildings too close to adjoining buildings. The fourth rule is broken by the use of opaque shades which, when drawn to escape the brilliancy of the sun, leave the room darker than it would otherwise be on a dark and cloudy day. Because of this fact the schoolrooms with a southern exposure are perhaps our most poorly lighted rooms. The fifth rule, concerning the use of white screens for the black-boards, is never observed and to many may seem insignificant. The justification of the rule is found in the following facts.


Dark Corners in Schoolrooms

The ordinary school room has the light from one side. The five rows of desks are so arranged that one row is next to the windows and the last row next to the black-board on the side of the room opposite the windows. It is well known that the desks next to the black-board and farthest from the windows receive less light than the desks next the windows. That the difference between the first and fifth rows is great enough to occasion any alarm seems not to have been suspected. In the ordinary schoolroom the light reflected from the pupil's book on the first row is eight times as great as the light reflected from the book of the pupil who is so unfortunate as to sit in the row next to the black-board. The decrease of the light as the distance from the window increases is different in each room. The law of the square of the distance is not even approximately correct but it is safe to say that in the great majority of school rooms in the United States the row of desks next to the windows has many-fold more light than the rows next to the black-boards. Professor Basquin and I tested school rooms having windows on but one side. In these rooms the variation be- tween the first and fifth rows was from seven-fold to ten-fold. By the introduction of screens over the black-boards in the same rooms, the light at the darkest seat was increased as much as 50 per cent. That an increase of 50 per cent, in the light in the dark corners of our school rooms is important is apparent to all. Furthermore, this result can be secured with little or no cost. Most schools possess white screens, light-colored advertising maps, charts printed on white paper, etc. They may be used to cover the black-boards and when thus used they will reflect the light to the very parts of the rooms which need it most.

Because of the lack of attention which is paid to the light actually present in the schoolroom, and because of the great difficulty in adjusting our windows and shades to the varying intensities of the external source of light, it is not surprising that we should find in our schoolrooms conditions of light so bad that during many hours and days the reading of ordinary printed matter without undue strain upon the eyes is impossible.


Unwise Demands made upon the Eyes of Young Children

Until within a very few decades reading was taught by a slow and cumbrous method. The effort of reading was so great that few chil- dren enjoyed the reading of a book until after they had completed the third school year. Interesting books for children were few in number and not available for the vast majority of them. To-day this is all changed. Our methods of teaching reading are so improved that be- fore the child has been in school a full year he begins to read books at home for his own pleasure. Our printing presses are teeming with children's books. Andrew Carnegie, or rather the movement which he so ably supports, has filled city and country with free books avail- able for even the youngest. During the last twelve months I have tested the eyes of some 700 children. I have asked of each child an estimate of the number of books read in the preceding 12 months. One room of 31 pupils for the 12 months preceding the middle of the second school year, gave the following figures. The average number of books read by each pupil was 22. Some had read but few, while others had read many more than 22. One half of the pupils had read 20 books or more. It should be observed that this record of the num- ber of books covers the period from the middle of the first school year to the middle of the second school year. After the second school year many pupils read regularly a book a week. In several of the grade rooms tested, the pupils of the room read on the average as many as 50 books a year. In the first three years after reaching the legal school age not a few pupils in our best city schools read 100 books. This figure is certainly far above the average, but there is a tendency to increase the number of books read during these first three years of school. We should but deprecate the tendency and do all we can to stop it. During these three years the pupils are growing faster than during the following years. At this time there is a decrease in the nervous energy of the child. In recent studies of the order of development of motor adjustments and coordinations, it has been found that the individual first acquires control over the larger muscles and later over the finer ones. The normal activity of the child exercises mainly the larger muscles. The plays of children give the widest scope to the exercises of such muscles. The coarser movements are most predominant while the finer adjustments and the use of the smaller muscles are of secondary importance.

By our improved forms of modern education all this is changed.

"We put the six-year-old child to the task of reading and writing. These acts involve the use of the smaller muscles of the organism and are dependent upon more exact control of these muscles than any other act the individual is ever likely to be called upon to execute in later life. If an adult is out of practise in the use of the pen, a single hour's work is sufficient to exhaust the hand. The extreme exertion which the child puts forth to guide the pen or to follow line upon line with the eyes is so far in excess of the amount of energy required by an adult that we are not in a position to appreciate the severity of the child's task. Children upon entering school have better control of movements involving the whole arm and the wrist than of those involving the wrist and fingers. The muscular control of the eyes is adequate for all free movements of the eyes, but not sufficient to warrant the finer adjustments of continuous reading. The loss of nervous energy, necessitated by reading and writing, at the ages of from five to eight years is an unwarranted drain upon the health of the child. At this age the child needs free and vigorous movements rather than the constrained and finer ones required in reading and writing. At a later age the control over the finer muscles is adequate for the task, but in this age of rush we are crowding our little ones and inverting the order of nature. Furthermore, the tissues of the globes of the eyes are still soft and the strain of the ciliary and other eye muscles is likely to cause short-sightedness by increasing the anterior-posterior axis of the eyeballs. If the child's eyes do thus lengthen under the excessive strain, the eyes are not only weakened for vision, but they become diseased organs.

We have thus far attempted to establish the following four propositions. (1) The human eye was evolved for distant vision and the perversion incident to reading and writing would lead us to expect some great injury to the organism. (2) Although the eye may easily adjust itself to a light changing from one-to ten-candle power, the diversities of daylight during the hours of the school day and the months of the school year are so great that the minimum and maximum extremes are frequently exceeded. (3) The necessary rules for lighting buildings are not adhered to, thus placing an unnecessary strain upon the eyes of all attempting to read and write. (4) There is a growing tendency to use the eyes at a period of life which is in every way ill fitted to the task. If these four propositions have been established, and if the pessimistic forebodings are justified, then investigations of the eyes should discover a general destruction of the eyes of civilized countries and an increasing number of eyes injured during the age of from 6 to 9.


Investigating the Eyes of School Children.

Systematic investigations of eyes upon a wide scale were not begun till 1865. At that date Dr. Herman Cohn commenced his investigations of the eyes of school children in Breslau. After having examined ten thousand children, he summarized his results as follows:

Short-sightedness hardly exists in the village schools: the number of cases increases steadily with the increasing demands which the schools make upon the eyes, and reaches the highest point in the gymnasia.

The number of short-sighted scholars rises regularly from the lowest to the highest classes in all institutions.

The average degree of myopia increases from class to class, that is, the short-sighted become more so.

The circular of information of the United States Bureau of Information, No. 6, 1881, in speaking of the many investigations which had been made in this and other countries said:

All, without a single exception, prove beyond a doubt that near-sightedness, beginning, perhaps, at nothing in the lower classes in the school and first year of school life, steadily increases from class to class in the school until in the highest grades or in the last years of school attendance it has actually developed itself in as many as 60 or 70 per cent, of all the pupils.

In all these tests children were not regarded as near-sighted unless their visual acuity in one or both eyes was but two thirds of normal vision or less. Think of the significance of these statements which are entirely authoritative. Pupils entering our schools come to us with good eyes, but if they stay with us till the end of the course, GO to 70 per cent, of them will leave us with but two thirds normal visual acuity or less. Most of this loss of vision is caused directly by the strain put upon the eyes in reading, writing and drawing.


The Sacrifices caused by Premature Strain

The picture drawn by the investigators during the two decades following 1865 was dark indeed. The only ray of hope was found in the fact that the destruction of the eyes did not begin during the first few years of school, so that pupils dropping out before the eighth or tenth year would probably escape with good eyes. Thus Cohn found that in the case of pupils 812 years old there were but 5 per cent., myopic, while of the pupils remaining the full 14 years, 63.6 per cent, were myopic. Investigations of the pupils of other cities of Germany resulted in similar findings. Investigations in America were not so numerous as those in Germany, but in general the results were the same until recent years.

Investigations carried on in Worcester, Massachusetts, in 1891, showed that in the second and third grades from 50 to 60 per cent, of the pupils possessed less than normal visual acuity. Investigations upon over 3,700 pupils of the Chicago public schools, in 1899, showed that the maximum of defective eyes was reached with pupils 9 years old. No one seems to have remarked upon this change in the grade at which the maximum destruction of the eyes is found. In fact the results seemed to have been looked upon as rather accidental and of no special significance.

Some months ago I asked myself these two questions. Is the maximum destruction of the eyes of the school children reached earlier than formerly? Secondly, if such is the case, what is the cause of it? In attempting to answer these questions I have tried to learn what recent investigators have found concerning eyes, and I have attempted personally to examine the eyes of children in schools which were significant. The data which I have secured lead me to conclude that the excessive destruction of the eyes begins several years earlier than was formerly the case in America, and earlier than is still the case in Germany and other foreign countries. As to the cause of the early injury of the eyes the results of my investigations are most significant. The highest per cent, of defective visual acuity I have thus far discovered was found in a room in which the pupils had been in school but 1112 years. This is the room referred to above in which the average number of books read by each pupil during the preceding 12 months was 23. It may not surprise you when I tell you that 84 per cent, of these little innocents had defective vision. The schoolroom in which they were seated was unusually well provided with windows and had a south exposure. Unfortunately their teacher preferred a rather dimly-lighted room and made generous use of opaque shades with which the windows were provided. The light by which the pupils read in school was in most cases certainly better than the light which they had for their reading of books at home. Some of these children in their childish ignorance took books to bed with them, and upon awakening in the morning read before breakfast. It is probable that in most cases the children at home read during the evening twilight till it was too dark to tell one word from another. Then they would retire to some dark corner of a dimly lighted room and continue the reading till supper time or bed time. Young children have no regard for their eyes and parents are not likely to interfere with them as long as they are quiet.

My query as to the cause of the early destruction of the eyes is being answered by my investigations. It seems to be simply because our infants are reading more books than formerly, both in and out of school. In Germany the instruction during the first few years of school life is largely oral and at home the children do not read so much as our children. Furthermore, our children are to-day much better taught than three decades ago, and they read much more than formerly during the tender years of from 6 to 9.

The pessimistic forebodings expressed in the first part of this article are more than justified by the figures just presented. The eyes of our school children are being destroyed, and worse than that, the destruction is now taking place at the age of from 7 to 9 years, which makes the matter so serious that we should bestir ourselves to lessen the evil as far as possible. In the palmy days of Greece the Athenian boy was not taught to read till he was ten years old. By our modern improved form of education we injure the eyes of our children so that one half of them have defective vision before the age at which the Greek boy learned his alphabet.

The gravity of the situation is so great that I venture to offer in conclusion the following suggestions:

1. We should recognize the fact that human eyes are ill adapted for reading, writing and drawing for a long period at a time.

2. We should recognize the fact that the normal daily deviation of daylight is so great that any method of adjusting the windows shades from mere habit is inadequate.

3. In constructing school houses the window space should be as large as that described above.

4. The interior walls and ceilings should be light.

5. The amount of sky visible from each seat should be large.

6. The windows should be provided with white Holland screens or their equivalents.

7. Every schoolroom should be provided with light shades and they should be placed over the blackboards as soon as there are dark corners in the room.

8. School children's eyes should be tested annually and parents notified that an oculist should be employed in the case of all defective eyes.

9. Children should not be taught even the elements of reading or writing during the first year of school. For the ordinary reading and writing should be substituted more oral instruction in language, number work, nature study, history, singing, physical training, play and other forms of training suited to the needs of the pupil.