Rabbit's eyes have been exposed to the most intense light known, avoiding heat, but subsequent examination of the eyes with the microscope revealed no change either in the retina, the optic nerve, or the brain. A teacher of fifteen years' experience complained that because her classroom was in the basement and the light poor, the sight of her pupils was worse at the end of every school year than it was at the beginning. The classrooms where the light was good, however, had the same experience; and when the Snellen test card was introduced into both the well-lighted and the poorly-lighted classrooms, and the children used it every day, the sight of all improved, regardless of lighting conditions. In Germany it was demonstrated by the statistics of Cohn and others that improvements in the lighting of the schools made in the hope of staying the progress of myopia did not have that effect.
These and other observations show that poor lighting has very little, if anything, to do with the production of eye defects.
The fact is that anyone who can read comfortably in a poor light is to be congratulated, and need not be afraid to continue the practice. If he were straining his eyes, he could not do it, whereas in a good light one can read in spite of the strain.
People who have perfect sight think very little about the light, but it is undoubtedly more comfortable to have it so arranged that no shadow is thrown upon the work, either from the head, hand, or any other object, and so that it shines upon the page which one is reading, or upon the desk at which one is writing, not into the eyes.
Protection of the eyes from strong light is not necessary. In fact, the light is beneficial, as we have already demonstrated. The glare from snow or water may be trying, and smoked or amber glasses will conduce to comfort, but, ordinarily, no harm will be done if they are not worn.
Since the moving pictures came in we have heard much about the strain imposed upon the eyes by this new appurtenance of civilization, and predictions of dire results to our already very bad eyesight, in consequence of our constant attendance upon these exhibitions, have been made. Theoretically, this view of the matter seems a reasonable one. The ordinary rate at which the film runs through the projecting machine is about a foot a second—sixteen pictures a second. That is to say, sixteen distinct pictures are thrown upon the screen in each second of time, and the shutter comes down and is raised that number of times each second also. Between each projected picture there must be a black period, for if this were not the case, the pictures would all run into one another, in a hopeless blur.
It might have been expected that these rapid alternations of light and darkness would be very trying to the eyes, and they often do produce much temporary discomfort, particularly in persons suffering from errors of refraction. Some years ago when the mechanical process involved was less perfect than it has since become, the strain was probably much greater than it is now. Today there is no reason for supposing that the movies are injurious to the eyes. On the contrary they have been found to be a great benefit. Instead of avoiding them, persons who do not suffer from them should go to them frequently, and those who do should accustom their eyes to them gradually, at the same time practicing the methods recommended in this book for the improvement of the vision. Often all that is necessary to relieve the strain is to close the eyes frequently, or look away from the screen, while viewing the pictures.
As for the dangers of fine print, those who understand the principles of central fixation will understand that it is easier, normally, to see small things than larger ones, and that the fear of fine print is, therefore, as baseless as the fear of light.
The fact is that the eye is a much less fragile instrument than we have generally supposed it to be. If properly used, it is fully able to withstand all the strains of modern life.
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