VISION UNDER ADVERSE CONDITIONS A BENEFIT TO THE EYES
ACCORDING to accepted ideas of ocular hygiene, it is important to protect the eyes from a great variety of influences which are often very difficult to avoid, and to which most people resign themselves with the uneasy sense that they are thereby "ruining their eyesight." Bright lights, artificial lights, dim lights, sudden fluctuations of light, fine print, reading in moving vehicles, reading lying down, etc., have long been considered "bad for the eyes," and libraries of literature have been produced about their supposedly direful effects. These ideas are diametrically opposed to the truth. When the eyes are properly used, vision under adverse conditions not only does not injure them, but is an actual benefit, because a greater degree of relaxation is required to see under such conditions than under more favorable ones. It is true that the conditions in question may at first cause discomfort, even to persons with normal vision; but a careful study of the facts has demonstrated that only persons with imperfect sight suffer seriously from them, and that such persons, if they practice central fixation, quickly become accustomed to them and derive great benefit from them.
Although the eyes were made to react to the light, a very general fear of the effect of this element upon the organs of vision is entertained both by the medical profession and by the laity. Extraordinary precautions are183
184 Adverse Conditions a Benefit to the Eyes
taken in our homes, offices and schools to temper the light, whether natural or artificial, and to insure that it shall not shine directly into the eyes; smoked and amber glasses, eye-shades, broad-brimmed hats and parasols are commonly used to protect the organs of vision from what is considered an excess of light; and when actual disease is present, it is no uncommon thing for patients to be kept for weeks, months and years in dark rooms, or with bandages over their eyes.[ NOTE ]
It is not light but darkness that is dangerous to the eye. Prolonged exclusion from the light always lowers the vision, and may produce serious inflammatory conditions. Among young children living in tenements this is a somewhat frequent cause of ulcers upon the cornea, which ultimately destroy the sight. The children, finding their eyes sensitive to light, bury them in the pillows
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and thus shut out the light entirely. The universal fear of reading or doing fine work in a dim light is, however, unfounded. So long as the light is sufficient so that one can see without discomfort, this practice is not only harmless, but may be beneficial.
Sudden contrasts of light are supposed to be particularly harmful to the eye. The theory on which this idea is based is summed up as follows by Fletcher B. Dresslar, specialist in school hygiene and sanitation of the United States Bureau of Education:
"The muscles of the iris are automatic in their movements, but rather slow. Sudden contrasts of strong light and weak illumination are painful and likewise harmful to the retina. For example, if the eye, adjusted to a dim light, is suddenly turned toward a brilliantly lighted object, the retina will receive too much light and will be shocked before the muscles controlling the iris can react to shut out the superabundance of light. If contrasts are not strong, but frequently made, that is, if the eye is called upon to function where frequent adjustments in this way are necessary, the muscles controlling the iris become fatigued, respond more slowly and less perfectly. As a result, eyestrain in the ciliary muscles is produced and the retina is over-stimulated. This is one cause of headaches and tired eyes." l
1School Hygiene, Brief Course Series in Education, edited by Monroe, 1916, p. 240
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There is no evidence whatever to support these statements. Sudden fluctuations of light undoubtedly cause discomfort to many persons, but, far from being injurious, I have found them, in all cases observed, to be actually beneficial. The pupil of the normal eye, when it has normal sight, does not change appreciably under the influence of changes of illumination; and persons with normal vision are not inconvenienced by such changes. I have seen a patient look directly at the sun after coming from an imperfectly lighted room, and then, returning to the room, immediately pick up a newspaper and read it. When the eye has imperfect sight, the pupil usually contracts in the light and expands in the dark, but it has been observed to contract to the size of a pinhole in the dark. Whether the contraction takes place under the influence of light or of darkness, the cause is the same, namely, strain. Persons with imperfect sight suffer great inconvenience, resulting in lowered vision, from changes in the intensity of the light; but the lowered vision is always temporary, and if the eye is persistently exposed to these conditions, the sight is benefited. Such practices as reading alternately in a bright and a dim light, or going from a dark room to a well-lighted one, and vice versa, are to be recommended. Even such rapid and violent fluctuations of light as those involved in the production of the moving picture are, in the long run, beneficial to all eyes. I always advise patients under treatment for the cure of defective vision to go to the movies frequently and practice central fixation. They soon become accustomed to the flickering light, and afterward other light and reflections cause less annoyance.
Reading is supposed to be one of the necessary evils of civilization; but it is believed that by avoiding fine print, and taking care to read only under certain favorable conditions, its deleterious influences can be minimized. Extensive investigations as to the effect of various styles of print on the eyesight of school children have been made, and detailed rules have been laid down as to the size of the print, its shading, the distance of
Supposed Dangers of Reading 193
the letters from each other, the spaces between the lines, the length of the lines, etc.. As regards the effects of different sorts of type on the human eye in general and those of children in particular, Dr. A. G. Young, in his much quoted report1 to the Maine State Board of Health makes the following interesting observations:
Pearl. as the printers call it, is unfit for any eves, yet the piles of Bibles and Testaments annually printed in it tempt many eyes to self-destruction.
Agate is the type in which a boy, to the writerís knowledge, undertook to read
the Bible through, His outraged eyes broke down with asthenopia before he went
far and could be used but little for school work the next two years.
Nonpareil is used in some papers and magazines for children, but, to spare the eyes, all such should, and do, go on the list of forbidden reading matter in those homes where the danger of such print is understood.
Minion is read by the healthy, normal young eye without appreciable difficulty, but even to the sound eye the danger of strain is so great that all books and magazines for children printed from it should be banished from the home and school.
Brevier is much used in newspapers, but is too small for magazines or books for young folks.
Bourgeois is much used in magazines, but should he used in only those school books to which a brief reference is made.
Long Primer is suitable for school readers for the higher and intermediate grades, and for text books generally.
Small Pica is still a more luxurious type, used in the North American Review and the Forum.
Pica is a good type for books for small children.
Great Primer should be used for the first reading book.
1Seventh Annual Report to the Maine State Board of Health, by the
secretary, Dr. A. G. Young, 1891, p. 193.
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All this is directly contrary to my own experience. Children might be bored by books in excessively small print; but I have never seen any reason for supposing that their eyes, or any other eyes, would be harmed by such type. On the contrary, the reading of fine print, when it can be done without discomfort, has invariably proven to be beneficial, and the dimmer the light in which it can be read, and the closer to the eyes it can be held, the greater the benefit. By this means severe pain in the eyes has been relieved in a few minutes or even instantly. The reason is that fine print cannot be read in a dim light and close to the eyes unless the eyes are relaxed, whereas large print can be read in a good light and at ordinary reading distance although the eyes may be under a strain. When fine print can be read under adverse conditions, the reading of ordinary print under ordinary conditions is vastly improved. In myopia it may be a benefit to strain to see fine print, because myopia is always lessened when there is a strain to see near objects, and this has sometimes counteracted the tendency to strain in looking at distant objects, which is always associated with the production of myopia. Even straining to see print so fine that it cannot be read is a benefit to some myopes.
Persons who wish to preserve their eyesight are frequently warned not to read in moving vehicles; but since under modern conditions of life many persons have to spend a large part of their time in moving vehicles, and many of them have no other time to read, it is useless to expect that they will ever discontinue the practice. Fortunately the theory of its injuriousness is not borne out by the facts. When the object regarded is moved more or less rapidly, strain and lowered vision are, at
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Seven Truths of Normal Sight
l - Normal Sight can always be demonstrated in the normal eye, but only under favorable conditions.
2 - Central Fixation: The letter or part of the letter regarded is always seen best.
3 - Shifting: The point regarded changes rapidly and continuously.
4 - Swinging: When the shifting is slow, the letters appear to move from side to side or in other directions with a pendulum-like motion.
5 - Memory is perfect The color and background of the letters, or other objects seen are remembered perfectly, instantaneously and continuously
6 - Imagination is good. One may even see the white part of the letters whiter than it really is, while the black is not altered by distance, illumination, size, or form, of the letters.
7 - Rest or relaxation of the eye and mind is perfect and can always be demonstrated.
When one of these seven fundamentals is perfect all are perfect.
Fig. 49. Specimen of Diamond Type
Many patients have been greatly benefited by reading type of this size.
Fig. 50. Photographic Type Reduction
Patients who can read photographic type reductions are instantly relieved of pain and discomfort when they do so and those who cannot read such type may be benefited simply by looking at it.
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first, always produced; but this is always temporary, and ultimately the vision is improved by the practice.
There is probably no visual habit against which we have been more persistently warned than that of reading in a recumbent posture. Many plausible reasons have been adduced for its supposed injuriousness; but so delightful is the practice that few, probably, have ever been deterred from it by fear of the consequences. It is gratifying to be able to state, therefore, that I have found these consequences to be beneficial rather than injurious. As in the case of the use of the eyes under other difficult conditions, it is a good thing to be able to read lying down, and the ability to do it improves with practice. In an upright position, with a good light coming over the left shoulder, one can read with the eyes under a considerable degree of strain; but in a recumbent posture, with the light and the angle of the page to the eye unfavorable, one cannot read unless one relaxes. Anyone who can read lying down without discomfort is not likely to have any difficulty in reading under ordinary conditions.
The fact is that vision under difficult conditions is good mental training. The mind may be disturbed at first by the unfavorable environment; but after it has become accustomed to such environments, the mental control, and, consequently, the eyesight are improved. To advise against using the eyes under unfavorable conditions is like telling a person who has been in bed for a few weeks and finds it difficult to walk to refrain from such exercise. Of course, discretion must be used in both cases. [ NOTE ]
Discretion Must be Used 197
But just as the invalid may gradually increase his strength until the Marathon has no terrors for him, so may the eye with defective sight be educated until all the rules with which we have so long allowed ourselves to be harassed in the name of "eye hygiene" may be disregarded, not only with safety but with benefit.