Popular Science Monthly/Volume 67/December 1905/The Cause, Nature and Consequences of Eyestrain
|THE CAUSE, NATURE AND CONSEQUENCES OF EYESTRAIN.|
NO questions are so often asked of the oculist by his patients as, 'Why do so many people, and even children, have to wear spectacles nowadays?' 'Are we deteriorating?' 'Are eyes so much poorer than formerly?' 'My grandfather did not wear glasses,' etc. Each oculist meets the questioning in his own way, but the public still remains unconvinced, suspects there may be some mistake about the whole matter, and is at least mystified.
It is hard to give satisfactory answers, at the best and with all one's good will. Not a little of our inability to throw light on the subject comes from our own indecisions and nonunderstandings. About many of the phases of the matter we have not reached a common conclusion and our professional differences of opinion bring further doubt to our patients. Concerning other parts we are also utterly unknowing ourselves, because the mechanics and neurologies of sensation, mentation and even of nervous force and transmission, still remain utter mysteries to all. Of these things the most learned are as ignorant as the most unlearned. We see or conclude that certain trains of ether-waves with a vibrational periodicity of some 400 to 700 trillions per second are transformed somehow into retinal and neural bundles of forces traveling only at the rate of about 125 feet per second; thence proceeding to the cortical visual center they are again transformed into what we call sensations of form, light and color. And innervational forces are sent back to the muscles of the eyeball, which move it as a whole, or modify its internal functions. Although we can know nothing of the intimate nature of these mechanisms and forces, we can deduce many definite, though crude, conclusions as to their causes and their results.
The dominating demand which governs all the processes concerned is for an accurate and accurately kodak takes a picture. To realize the difficulty of the kodak of the living eye, one must have an adequate conception of the variations, only one two-hundredth or one four-hundredth of an inch from the normal in the dimensions of the eyeball or in its corneal curves which may prevent the accurate photographic 'definition' of the retinal image. To this must be added a knowledge of the means or lack of means possessed by the eye to overcome or neutralize these results of deviations from the standard of size and contour. What are the kinds of deviations that may be cancelled, how far the neutralizing is possible, what kinds may not be overcome, and the mechanism of the overcoming, these are all pretty well understood.image upon the retina of the object upon which the eye is trained. All human physiology centers in that success, and much of our pathology follows from its failure. That there shall be two such images upon 'identical points' of the two retinas only heightens and complicates the difficulty. The clearly defined perfectly-representing image upon the retina is purely a matter of optics, physical and physiologic, and may be understood by any one who knows how his
In the briefest way we may say that if an eyeball is too long (from the cornea to the retina) it is near-sighted or myopic. One can not see well at a distance, for everything appears blurred and hazy. The focus of the image is in front of the retina, and there is no device of the unaided eye which can transpose it to its proper position upon the retina. Any effort to do so is by the nature of the conditions a negative one, an endeavor, if one may so speak, and of course, unconsciously, to lessen muscular effort. There is as result no eyestrain, no morbid, or wearying, or hurtful attempt at muscular exertion.
The supposition, in this case, is that a pure or uncomplicated myopia exists, and that it is of the same degree or amount in both eyes. In truth, however, that supposed condition never exists. No oculist probably ever tested a pair of eyes having no astigmatism, and having exactly the same over-length, or myopia. And this astigmatism, or the difference in lengths of the two eyeballs, or both factors combined, brings always the possibility of 'eyestrain.' For eyestrain is the name given to any unphysiologic, i. e., pathologic ocular action or function which is wearying, excessive or unnatural. It thus becomes clear how it is that the two eyes by reason of the presence of a difference in their relative lengths, or because of astigmatism in one or both, may result in morbid effort or strain, although if both were alike in over-length, and without other optical defect, there could be no such strain. This general fact makes evident the truth that in general those with (moderately) myopic eyes have far less ocular diseases and pains in the eyes, less headaches and other general disorders, than those whose eyes are hyperopic, or 'far-sighted.' For in all 'far-sighted' eyes there is a never-to-be-renounced effort to overcome the trouble. But this freedom from pain and other symptoms in myopia may lull the patient with a false security and costly neglect. The great danger is that without the attention of a skilled specialist the myopia may increase, become 'malignant,' as it is termed, and the eyeball continue to elongate, with imperilled or fatal loss of vision. The myopic eye is one abnormally elongated, enlarged or stretched, and once having lost its tonicity or normal measurement, it tends to extremes of enlarging.
The far-sighted or hyperopic eye is the reverse of the myopic eye: it is too small or too short and hence effort and muscular exertion are necessary to bring the image forward, in proper definition upon the retina. Without this exertion the image would be behind the retina. Hence a similar blurring or badly defined picture as in myopia, but from the reversed cause. In this kind of eye the picture is naturally blurred even of the most distant object (making the term far-sightedness a misnomer), and a slight increase of power is required on the part of the 'accommodation' mechanism in each eye, in order to shorten the focus of the image-forming rays of light. With every lessening of the distance of the object, still greater converging power is demanded, as one may understand by tests with different-power glass lenses. When the object is brought within ten or fifteen inches of the eye the greatest effort is required to make the image clear. The degree of this effort will depend upon how much too short the eyeball is, or upon the amount of hyperopia. It will also depend upon the kind and amount of ocular labor, especially the continuance of 'near-work,' the reading, writing, etc., required of the eyes. The farmer, ranchman or sailor will obviously be able to overcome or be indifferent to higher degrees of far-sightedness than those living in cities, while the literary man, bookkeeper or seamstress will experience eyestrain with still lower degrees of hyperopia.
One must carry in the mind another modifying condition—the difference almost always existing between the far-sightedness of one eye and that of its fellow. The two are under more stringent orders than in myopia to work together and in harmony. When the hyperopia differs in the two the chances of strain are obviously increased many times.
These chances already multiplied now become inevitables if astigmatism is a complication of the hyperopia. Alas, also, it is very certain to complicate. I have measured something like ten thousand pairs of eyes, and not one of these pairs was without some imperfection of shape, size or curvature, either in one or both of the eyes. An absolutely perfect pair of eyes does not probably exist.
'And do tell me, what is astigmatism?' is the puzzling question put to the oculist every day. It is one, fortunately, very simply and easily answered. The front part of the eye, that behind which lies the pupil, is called the cornea. It should be round or equally curved like the central portion of the end of an egg. It is usually not uniform in its curvature, but is more curved in one meridian than in the reverse meridian—that is, it is, approximately, of the shape of the side of the egg. When symmetrically curved it will naturally refract, or help to focus, correctly, the entering cone of light which is to form the picture on the retina. If it is unsymmetrically curved, like the side of the egg, it will produce a misshapen and unsymmetrical picture which does not accurately represent the object. The condition of safety, right movement and proper 'senseing' of the world thus depends upon the exactness of this image-making power of the eye. It seems probable, indeed, that one of the greatest factors in the survival of the fittest or in the elimination of the unfit, in biologic and social evolution, has been this overlooked optical inaccuracy of the eye. In the chase, in battle, in games, in all tribal and industrial competitions and tasks, the imperfectly-seeing must have gone down before those whose eyes saw more perfectly and whose answering hand and foot executed the precedent ocular command more speedily and precisely.
The malcurvature, or astigmatism, of the eye, may obviously be of widely varying degrees, and may be placed in any possible one of the 180 degrees of its half-circle. So infinite are the permutations of these amounts and placings, and so complicated may astigmatism be with any kinds of short-sightedness or long-sightedness that, as emphasized, in all probability no one eye in the world has identically the same optical measurements and powers as another. No pair is without optical imperfections and none has exactly the same ones as those of any other. The chief and continuous cause of astigmatism is the pressure of the upper lid upon the cornea just at the upper edge of the pupil. The astigmatism in the vast majority of all eyes shows that the cornea is curved more in its approximately vertical than in its horizontal meridian. The few cases in which this kind of curvature is not present are really 'exceptions which test the rule' The habitual placing of the upper lid at this precise line of the cornea is caused by the necessity of shading the cornea or protecting it from the light which would enter from above and dazzle or harm the delicate retina. Every one when facing a bright light has found how bad vision is for at least some minutes afterwards. This semi-paralysis of retinal function would make activity slow and inconsequent, if not often jeopardize life. It has been a helpful factor during the evolutionary struggle in preserving the organism.
A study of the position of the upper eyelid and coordinated pupillary movements in animals would show each type meeting or avoiding the difficulty by many devices. In such animals as fishes, birds, owls and many forest-roving animals there is danger from above as well as below, so the upper lid is kept well retracted and the pupil wide open. In the owl the pupil is large even in daylight, and hence this bird is then in a dazed condition of mind, and flight is dangerous. The mechanisms designed to give definition to the retinal image, to shade the retina so that it may recuperate its sensibility for the next instant's instantaneous image, accentuate the fact that the formation of the retina was perhaps the most difficult task encountered in the development of higher forms of life on the globe. All organic success depended upon that special success.
And few have the most dim notion of the complexity of the organ of vision in man, or of the amazing difficulties of 'Biologos' in fashioning and perfecting it. Millions of finger tips are bunched together in the one-inch cup of the eyeball, from whence run about 425,000 nerve fibrils to a topographic mechanism of sensation in the occipital lobe. The eye can see an object 1/1,000 of an inch in diameter. The cones and rods are only 1/10,000 or 1/14,000 of an inch in diameter, and a million cones at the macula occupy a space of only 1/10 of an inch square. These crowded finger tips perceive the shape of the picture and the intensities of the light stimuli of all illuminated objects, of a millionth of a millionth of the kinetic power of any other physiologic force, and of so short a duration as the 0.00144 of a second. And out of these infinitesimal waves the sensations called light and color are created. The mechanism which creates them must be in intimate and instant connection with the centers initiating and controlling every other sensation, of every motion, of every muscle of the body. Imagine for an instant what takes place in every animal and human being every day of its existence: e. g., a traveler tells of a monkey pursued by another, and running over and through the tops of the trees of an African forest faster than a deer could run on open ground. The flashing repetitive momentary glances of the eyes, before, back and all about a hundred objects must be coordinated with a mathematical precision to accurate unity and brilliant action of every muscle of the body. Similar perfection of eye and motion has been evolved in every higher animal of the world, and in every savage, and in every child. In man there is no danger from above, the eyes are rarely raised to the sky; the pupil consequently has a wide range of movement, and to shade the pupil the lid drops to its upper border. Doubtless we possess a more appropriate color sense, retinal discrimination and visual judgment because of the device.
The need of a shading of the retina to produce clear and quick imaging, 'resensitizing of the visual purple' it has been called, is so great that there are distinguishable a surprising number of separately acting mechanisms, all working to this end:
1. The shadows cast by the retinal arteries, veins and capillaries.
2. Reflections and shadings from the individual corpuscles of the blood in these vessels.
3. The shadings of vitreous cells called muscæ volitantes.
4. The pigmentary layer of the front part of the retina continuous with that of the iris.
5. The iris-pigmentation, lack of which constitutes the tragedy of albinism.
6. The continuous narrowing and widening of the pupil.
7. The pigmentation of the skin of the lid, and the comparative opacity of the lid-structure itself.
8. The eye-lashes have an additional screening function, while allowing vision or suggestion of an object above.
9. Winking shades the retina entirely every few seconds of the waking life.
10. The possession of two eyes with their associated movements constantly varies the light-stimulus, shading, etc., more than would be the case in a cyelopean eye.
11. Incessant movement of the eyes accomplishes the same object. Looked at steadily an object is lost from view, especially if it be brightly illuminated.
12. The eyebrow serves as a shading device. In old men, when the retinal sensibility is dulled, and more slowly recuperated than in youth, the eye-brow hairs often take on a luxuriant growth.
13. The retraction of the eyeball, by the absorption of the orbital fat, especially in the aged, serves in the same way toward additional shading.
14. The habitual position of the upper lid across the upper edge of the pupil works clearly to the same end. It is so necessary that it must be allowed although it brings with it a new source of evil.
For with this pressure of the lid comes astigmatism—one of the greatest causes of suffering in all civilized societies. There is probably little or no astigmatism in the eyes of those animals whose lids are habitually retracted—'wide open' as the birds, fishes and many of the mammalia. The outward pressure of the fluids within the eyeball tends to keep the cornea taut and symmetrically curved.
The 'accommodation' function of our eyes is their power to focus equally clearly the images of objects at a distance and those near the face. Its mechanism is the crystalline lens, controlled by the ciliary muscle. The lens has an innate and spontaneous elasticity which gives it the ability to increase its refractive power required as an object is brought nearer the eye. This increased refraction is incited by the contraction of the ciliary muscle. This act is called accommodation. As has been said, it is little exercised in myopia, and hence there is little pain or 'eyestrain' in purely myopic defects. In the condition called emmetropia, or optical normality (only approximately existing), it is called into use, and increasingly with every increase of nearness of the object looked at, until its extreme is reached when the object is so near the eyes that it is not clearly seen, that is, with accurate focus, or clear photographic definition.
With this point reached in our exposition we come upon the heart of the matter, which is this: In the ages of past evolution the safety of the organism has depended upon sharp distant vision—the more or less distant, from the horizon to a few feet from the eyes. The mechanism of accommodation has been evolved in answer to this need. The nearer an object the less continuously must accommodation act, the less uninterruptedly was the contraction of the ciliary muscle. The extreme of muscle tension or contraction, the full force of its innervation can only be carried out for the shortest periods of time. That is the great law which dominates the action of every muscle of the body. If its contraction is kept up continuously for too long a period the result is not only weariness, but spasm, exhaustion, pain, disease, etc., and physiology passes into pathology. Carefully analyzed there will be found no muscle in the body which can endure continuous contraction except for a short time. Tests of holding the arm out straight, carrying a light satchel in one hand, etc., are familiar. Most muscles called into continuous action show that the continuity is an interrupted one, and that there are necessary rhythms of contraction, relaxation and rest. The genius of evolution, so far as the eye is concerned, never foresaw the demands to be made upon the organ by our modern life. In but one or two hundred years since printing, urbanization, commerce and the rest have sprung into existence, the entire process, speaking, has been reversed; before this it was an intermittent and temporary function, while that of reading, writing, sewing and handicrafts demands a of the image of objects at twelve or fifteen inches from the eye; this for millions has now become a continuous one. For all hyperopic and astigmatic eyes the act of accommodation is required for ten or fifteen hours a day, often for hours with hardly a moment's interruption. This unwonted demand requires the continuous innervation and contraction of the ciliary muscle. To comply necessitates an impossible task, considered physiologically; the result is eyestrain with its host of sequent diseases, far-away reflexes, headaches, nervous diseases and kinds of ill-health too numerous to enumerate.
If the hyperopia were alone present, and especially if the amount were alike in each of the two eyes, cerebral ingenuity could cope with it with far less disastrous results than are everywhere shown. The eyes are seldom alike and the evils multiply. But they become genuinely morbid with the complication of the usually-present astigmatism.
The ciliary muscle is a 'sphincter muscle' fashioned in a circular manner about a central point, and by its very nature it must act by an equal, or comparatively equal, contraction of all its parts. Astigmatism is a defect acting in a line across the structure, and hence to neutralize or compensate, the ciliary muscle is called to act against its structure and nature upon two opposite sides, those parts at right angles not acting. Hence the impossibility of overcoming the defect, at least in but a limited and partial, and always unnatural, way. The higher the astigmatism the greater the limitation and impossibility. In the high degrees it is frankly out of the question, and the retinal together with the sensation-making function is hurt by the false and blurred image, and vision deteriorated. 'The old ophthalmology,' still ruling unquestioned in Europe and largely everywhere, looks upon the correction of astigmatism by glasses only as a means of giving better vision, and so corrects only the large errors. It forgets that in these large optical defects the ciliary muscle renounces effort, and that the smaller ones are precisely those which produce the worst morbid results, because the strain of accommodation, or continuous contraction of the ciliary muscle, can never be renounced. This constitutes the predominant source of eyestrain.
There are several other misfortunes or imperfections of the accommodation mechanism which may not be neglected if we wish to understand the matter in all its bearings. The crystalline lens must of course be transparent, hence it can not be nourished directly by the blood with its red corpuscles. Its healthful action is, therefore, dependent upon nourishment by blood-serum alone—plainly a difficult task, especially as this serum must reach it indirectly by osmosis, filtration, etc. It has also no nervous connection with the brain, and the three conditions named conspire to bring about two most noteworthy faults in its life-history. It is prone to become non-transparent or opalescent and, finally, almost opaque in the old, and this is cataract. Its elasticity also decreases steadily from childhood until it is so inelastic at about 45 years of age that the 'range' or degree of accommodation becomes too limited to enable it to focus the images of objects clearly on the retina except by holding the book, for instance, too far from the eye. This is the beginning of 'presbyopia'; at about sixty all the elasticity of the lens is lost and accommodation is at an end. Moreover, oculists have been hitherto unmindful of the fact that the accommodation may be less than normal in many young patients, even for short tasks. It is always so for long and continuous ones. For presbyopia, there is no prevention and no cure. There is a makeshift device (spectacles) whereby we may supply the lost focusing power of the living lens, by glass lenses placed in front of the crippled 'crystalline lens.' Of cataract, however, there is a pretty sure method of prevention, and this, again, is spectacles.
The science and art of correcting or neutralizing these optical defects of the eyes—myopia, hyperopia and astigmatism—is by means of artificial optical lenses. First, be it noted, it is a medical art and science, which no optician can compass. He has neither the legal nor the ethical right to attempt it, and surely he has not the scientific and medical knowledge requisite for its accomplishing. However poorly the medical man has executed his task, the optician will do it far more blunderingly. This verbum sapienti should be sufficient warning until, as with the druggist, we have also with the optician, passed laws to prevent him from attempting to fill the office of physician. There will then not be so many ruined eyes, and far less suffering from eyestrain.
Spectacle lenses have the power of changing the shape and direction of the image-forming cone or bundle of rays of light entering the eye so that its faulty optical construction and powers are neutralized, and the image is at last accurately whereby the direction of the parts of the rays making the image are so modified as to restore the picture about to be formed to normality. Plus is met by minus, minus by plus, astigmatic one-sidedness by its reverse. If the living eye were a dead mechanical one, if it were not subject to many diseases, if the results of eyestrain did not end in a multitude of diseases of the entire body and mind, then the optician might learn to prescribe glasses. But even for the highest medical intellect the work is a science and art demanding his best powers. Some one said that there are nine and forty distinct and separate ways of achieving damnation, while there is but one of salvation. There are twice that number of separate ways of failing to get right spectacles, and seventy-eight of them are set forth by an American oculist, reasons being given why, if any one is neglected, there will be no relief of eyestrain. Even if the physician's prescription is right, even if the lenses are properly ground and mounted, even if the spectacles are properly adjusted to the wearer's peculiarities of face, etc.—and these are all hazardous suppositions—there remains the wearer's carelessness, prejudices and ignorances, to thwart the entire proceeding. There are microscopists, and astronomers who will spend lifetimes of self and others, in care to correct the optical inaccuracies of their microscopes and telescopes, and yet whose own eyes that look through the instruments have far more glaring optical defects than Clark eliminated from his objectives by years of patient labor. The eye that sees everything can not see itself. So slow is man to study the student, himself. He will even investigate the brain and its functions before he will the eye: although embryology demonstrates that it was the brain which developmentally came out to see; the eye did not at first exist apart from the brain, and then send in to the mind the message of its discoveries. When once the million threads of brain substance were pushed out to the surface, the product called intellect resulted. For all useful thinking is in visual terms, and the sine qua non of civilization, the alphabet, is only a series of conventionalized pictures of things seen. The problem of our being here, the primal conditions of organic and social evolution, have depended and will always depend upon visual function. Is it then to be wondered at that our difficulties, bodily and social, our diseases, imperfections, our wants, failures and miseries, most frequently have also their source in visual difficulties and imperfections? Error is the softest and best word we have for human failure to reach the best attainable aims and ideals. It is more than an accident that the technical name for the great mass of ocular woes, and for the causes of multitudes of others, is 'errors of refraction.' The compulsion of fate as well as an error of evolution has brought it about that the unaided eye must persistently struggle against the astonishing difficulties and errors inevitable in its structure, function and circumstance. This struggle wrecks health, happiness and life, because by no device can the brain steadily innervate a muscle to continuous contraction. There results eyestrain—an error, the result of an error, the consequence of an older error; all may be done away with by an easily-obtained, at present usually unobtainable, device. The obtaining of that device is a matter of more importance to civilization than all the universities and wars of the last century. 'Exaggeration?' Not so!, and perfectly pictures the object. The outside lenses are in a way reversely unnatural, so that the inner eye-defect is met with an outer cancelling modification,
For what are the consequences of eyestrain? Wherever there is eye-labor 'at near-range,' as in reading, writing, sewing, mechanics, art, science, commerce, etc., there, beyond question in one half the workers, is eyestrain of a disease-producing kind. What kinds of diseases?
Firstly, those of the eye itself, for surely all good oculists agree that a large majority of local eye-diseases are themselves directly or indirectly due to eyestrain. The only exceptions are albinism, loss of accommodation generally (presbyopia), some tumors and a few minor affections. Cataract, it is being recognized, is due to the morbid function of denutrition set up by the strain to neutralize errors of refraction, and may be prevented by wearing correcting spectacles long prior to the 'cataract age.' Almost all other inflammations of the eye, not excepting often the infectious ones, are usually due to the same morbid function. Function, as all good physiologists know, always precedes structure, and malfunction, as all good physicians know, also precedes the morbid and fatal organic pathology. Eyestrain is almost always the cause of eyes turning in, or out, that is, squint or strabismus, a trouble that is 'innervational in nature and refractional in origin.'
The next of the series of bad results of eyestrain are cerebral. The brain comes out to see, but owing to the enormous difficulty of the task, it sees poorly and with exhausting or irritating labor. As its every process and act is bound up with and the product of vision, visual disorders by reflex and passed-on malfunction induce cerebral affections, evidenced primarily by headache, migraine, etc. Although the medical text-books give little or no hint of this, it is true, as thousands of good physicians and patients well know, that headaches, ninety per cent, at least, are due to eyestrain. Many observant physicians believe that the so-called 'paroxysmal neuroses,' periodic headaches, migraine, epilepsy, asthma, etc., as well as hysteria, neurasthenia, 'brain-fag,' 'nervous breakdown' are very frequently caused by years of morbid ocular struggle.
Mental diseases follow: weariness, alternating with hyperexcitability, an amazing need of walking, truancy (escaping from ocular labor), morbid introspection, nameless torments and self-tormentings, diseased habits, hopelessness, melancholia, manias, incipient and functional insanities and indirectly occupational failure, crime and many other errant trends.
The methods by which morbid ocular function induce various bodily diseases are so varied, differing almost in each individual, that it is impossible to set them forth in detail. Primarily it seems certain that the process is essentially one of waste and exhaustion of nervous force; all corporeal activities depend upon right-seeing. All subordinate cerebral centers are drawn upon to restore the balance when clear and easy seeing drains too severely the optical store-houses and regulating mechanisms. But the peculiarity of nervous action is that often undersupply and even exhaustion ends in irritation and excessive nerve action. Hence we find hyperesthesia attending or consequent upon lowered vitalities and tensions. But at least and always come disordered functions and these naturally form two types or proceed by two routes. The first disorders, often the more distinctive cerebral incoordinations, are those classed as nutritional or digestional. Certainly one half of all sufferers from eyestrain have dyspepsia of some kind. 'Liver,' 'stomach,' loss of digestive power, loss or fickleness of appetite, are the complaints that constantly occur in the biographies of great literary workers, and of the majority of our patients.
The second class comprises those whose blood-supply and tension is morbidized—the so-called 'vasomotor' cases. Skin-affections, as was long ago found, are often due to 'migraine,' and migraine, we now know, is due to eyestrain. It is remarkable how often diseases of the kidneys have been preceded by years of suffering from eyestrain. Secondarily almost any affections, even surgical diseases, may supervene, caused by the lowered nutrition, disordered blood-supply or the derouted nerve influences. The terminal diseases, as they are called, because they perform the final act of killing, are often but the executioners of long precedent eyestrain. Even the infectious diseases find their best soil—and soil is as important as seed—in the lowered vitality following years of headache, dyspepsia, etc. By careful count and trustworthy statistics 27 per cent, of school children have lateral spinal curvature. This astounding source of sickness and invalidism, directly or indirectly, is due to ocular defects, functions and laws.
And if the child is father to the man, let us add, and to the woman, what a havoc of the future generation we have been preparing by our neglect of the care of children's eyes! Take it only in the aspect of a saving of time. The results of Dr. Baker's examination of the eyes of the Cleveland, Ohio, school children show that those with defective eyes are six or seven months older than the others of the same grade and that one in four have eyes that keep them behind in their studies. In the last few years the examination of the eyes and health of school children shows an appalling condition which fully bears out all that oculists have been warning against. The examiners in Quincy, Mass., state:
In New York City Dr. Cronin finds that over 30 per cent, of the school children are suffering from the gross forms of defective eyesight. It must be remembered that the worst defects are not included in these statistics.
Lastly, the greatest of the misfortunes which may be traced to this cause are those connected with intellectual progress, the literary workers being those who suffer most. In direct and indirect ways the advances of civilization are most frequently conditioned upon use of the eyes in writing and reading. Certainly one half or more of the great writers and thinkers of the world have had their lives turned into tragedies of personal affliction by this unsuspected cause. The biographies of Swift, Nietzsche, Parkman, George Eliot, the Carlyles, Whittier, Darwin, Wagner, Taine, Symonds, Heine, De Quincey, Huxley, Lewes, Margaret Fuller, Jules Verne, de Maupassant, Balzac, Berlioz and many others are filled with pathetic evidences of the truth. It is noteworthy that in the monumental 'Life of Wagner' Dr. Ellis, who is at once physician, musician and biographer, after exhaustive research, confirms the theory that eyestrain was the chief cause of the poignant physical sufferings of that great genius. And what influences such afflictions have on the character of the men and of their works only the discerning can surmise. The large majority of the men and women mentioned above have a striking likeness as regards a certain harshness, even bitterness, and a peculiar and pitiless insistence on logical distinctions; all but one or two were pessimistic and unreligious. Only art saved Wagner from an acerbity and skepticism, illustrated by his enemy-friend Nietzsche and his philosopher, Schopenhauer. It does not require a great mind to recognize the profound influence of disease upon character and philosophy.