What you see and how you see
You think sight is one sense that can't deceive you, but it can and often does. Here is why different people see things differently-and same go blind with perfect eyesight
Ever since man became aware of the gift of sight, he has courted and cherished the thought that seeing is believing. The other senses may play him false—the tongue may lie and the ear deceive—but the eye reports only what is there and what is true.
This reassuring notion, more and more experts in the study of the eye have discovered, is far too optimistic. No two persons ever see the PHOTOBYPETERCROYDONSAME things in exactly the same way. For sight
is as much an individual affair as love or hate, passion or prejudice. Seeing is handled by your brain rather than by your eyes and your view ol the world is as different from someone else’s as your dreams, your IQ or your opinion of a Picasso painting. Brain injury can blind you as surely as the loss of an eye, and mental illness can twist your surroundings into nightmare shapes. Even if your vision is normal, the way things look depends on the way you think about them. What you see in an ink blot or a cloud
formation is a reflection of what you are.
Your eyes arc an outgrowth of your brain: they are translating machines that gather rays of light and transform them into nerve impulses. The message sent by them to the brain is meaningless until it’s interpreted by your mind.
Because it puts your brain in direct contact with the outside world—it provides twice as much information as all other senses combined —vision has tremendous speed and impact. You respond to a visual stimulus in a fraction of a second, yet the emotional effect of one shocking sight can last a lifetime. Whenever you open your eyes, you set in motion a process faster than sound, more efficient than photography, a thousand times more complicated than the most intricate electronic system.
The secret of seeing lies in the retina, the sensitive membrane that changes light rays into electrical impulses. Thinner than tissue paper, fragile as grapeskin, the retina is stretched across the back of the eyeball like the lining ot an eggshell. Its innermost layer is composed ot 137 million nerve endings from, the brain, tiny cells that absorb light and transform it to electricity through a chemical process.
Your brain is also responsible tor the tact that you see things right way up. Before rays ot light fall on the retina, they pass through an elaborate arrangement of transparent lenses and focusing mechanisms, which invert light rays so that the image they cast on the retina is actually upside down. But by the time a baby learns to see, his brain automatically reverses the retinal image in much the same way that a man shaves by looking at his reflection in a mirror.
On the jumble of colors, shapes and shadows presented to it by the eye, the brain imposes pattern and meaning. We look out of a window and see more or less what we expect to see— trees with their branches poised above their trunks, cars moving forward at uniform speed,
flashing lights spelling out familiar advertisements. We interpret these sights so easily that we forget we would find it impossible without years of mental training. A new-born baby's eyes aren't fully developed, but they could give him a fairly complete picture of the world around him if his brain were capable of organizing the things he saw. Within six months he can see things accurately and in color, and his eye muscles are also co-ordinated. But the child gradually learns to see only after about six years of struggling to make sense of the images his eyes receive.
Within a few weeks he can fix his gaze on his mother's face, but it takes him several months to distinguish between her face and that of a stranger. Bright moving objects catch his eye. and he especially likes red and yellow. (By the time he reaches school age his taste will probably have shifted toward blue and green, although sociologists have found that children from poorer districts and people in primitive societies continue to choose gaudy colors. It's believed that a preference for cool colors accompanies maturity and reasoning power.) By mentally linking up the way things look with the way they feel and taste and move about, the child comes to see that the world is filled not with moving blobs of color, but with objects of definite size and shape and a special significance for him in terms of food, warmth, comfort, amusement and affection.
The experience of people cured of congenital blindness shows that full vision is slowly acquired. In 1932 a Leipzig physician. M. von Senden, published a report on sixty-six patients, blinded from birth by cataract, whose sight was restored by operation. Since they had never seen anything, even in dreams, these people were at first bewildered by the sights that seemed to press in on them from all sides. 7'hey found it hard to estimate size and touch. When shown objects they were accustomed to handling, they were unable to identify them and sometimes couldn't even see the difference between a pencil and a key. Some took weeks to distinguish between a square and a triangle, and even longer to recognize that two triangles of different colors were the same shape. Like children, some spent years learning to read letters and numbers.
It takes us years to grasp the idea of space. Three-dimensional vision — the brain's ability to fuse the separate images seen by your two eyes into a single picture—is only one of the factors involved in depth perception. If you close one eye, your field of vision is reduced by about twenty-five percent and your ability to see depth is impaired, but you can still estimate distance from experience. While a baby thinks the moon and a ball are equally close to him because they appear the same size, an older person has learned that near objects look bigger than distant ones. When a child of five draws a man walking uphill, he may show the man perpendicular to the slope of the hill—defying gravity—rather than to the horizon line.
Seeing also depends on the sort of person you are. From the vast panorama presented by your eyes—it has been estimated that each eye can send a thousand million impulses per second to the brain—your mind chooses significant details. You can stare at a sign without becoming aware of its message, while on the other hand a fragmentary glimpse of some familiar object can give you the impression that you've seen the whole thing clearly.
“There is plenty of evidence in children’s drawings, and in adult errors in perspective drawing, to show that a person looking at an object thinks he sees more of it than he does,” Dr. D. O. Hebb, head of the department of psychology at McGill University, points out. "What he knows about the object appears in his drawing, as well as what is visible at the moment.”
To some extent the way you see a thing depends on the meaning it has for you. In experiments by U. S. psychologists ten-year-old children judged that coins were about twenty-five percent larger than valueless cardboard disks, although the disks were actually the same size; the poorer the child, the more he overestimated the size of the coin. Other subjects thought that a piece of cloth cut in the shape of a leaf was greener than an identical piece of cloth shaped like a donkey.
A schizophrenic can't believe his eyes. "He sees corners of a room shift and walls close in on him"
Vision can be affected by psychological reaction, such as hysterical blindness, a curious condition in which a person with healthy eyes is genuinely unable to see. A hysterically blind person is usually faced with problems he can’t cope with. His brain provides a temporary and involuntary escape by refusing to handle messages from his eyes, and thereby limits his field of action. Although an ophthalmologist can detect this form of blindness by various tests, such as shining a light in the eyes and finding that the pupils contract—a normal reflex action—it can be treated only by psychotherapy or by the removal of the emotional pressure that caused it. One hysterical woman, for instance, suddenly became blind after she and her husband had lived for some time with his mother, whose interference she resented. When they moved to a house of their own. she began a period of partial recovery with lapses back into blindness, and later regained her sight completely when the older woman died.
In World War II. men exposed to combat sometimes suffered emotionally induced blindness such as tunnel vision,
which cuts out peripheral vision as though one were looking through a tube. For men so battle-shocked that any sight or sudden movement may terrify them, funnel vision apparently provides protection by reducing the source of alarm.
Ft.-Col. Roy R. Grinker and Major John P. Spiegel, two FISA A F officers who studied the psychological effects of combat in a book called Men Finder Stress, described patients such as a sergeant whose fear of enemy aircraft caused him to see a black spot before his eyes in the shape of a plane, and a young pilot whose depth perception suddenly failed alter his best friend was shot down by a German fighter. Under the influence of pentothal, the pilot revealed his fear that he. too, would be killed and complained that his eyes blurred whenever he flew over enemy territory because there seemed so many dangers to watch out for all at once. When he recognized his fear as a natural reaction, his visual troubles disappeared and he returned to (lying duty.
They really do see red
Night blindness, another wartime handicap. may be fear-induced or even imaginary. A survey made by a British researcher indicated that ninety percent of his subjects who complained of poor night vision actually had normal night vision. Night blindness is ordinarily caused by a deficiency in vitamin A. Although most of us get plenty of vitamin A—one twenty-fifth of a gram of halibut-liver oil contains a full day’s supply —people suffering from hepatitis, hyper-
thyroidism and some other conditions sometimes have to take more of the vitamin. Once your night vision is normal you can’t improve it by taking extra vitamin A.
Other forms of mental illness are reflected in vision. To the schizophrenic, who has trouble organizing himself, the angles in a room sometimes shift out of balance so that the walls appear to be closing in. As well as distortions in things he actually sees, he may have bizarre visions. Epileptics also suffer from hallucinations in which things around them grow to gigantic size and move closer and closer.
Red, the most common color in epileptic hallucinations, is apparently linked with emotional disturbance. The epileptic fits of one woman who ordinarily dressed primly in dark colors were usually heralded by a vivid picture of herself with (laming red hair and a red dress, climbing on a red bus to drive down a red street past a red postbox fastened to a red telephone pole.
The more directly hallucinations stem from an organic cause such as alcoholism, the more likely they are to contain realistic, meaningful figures. While a schizophrenic may be haunted by dollsize visions, a man in the throes of delirium tremens is more likely to see people of normal size, probably with some unpleasant meaning for him. Any drinking bout may make him see double because alcohol relaxes the muscles that co-ordinate his eyes.
People who become extremely depressed sometimes find that things around them look dark and dull. They complain
of dim lighting and find it harder to read signs because they see less contrast between the letters and the background. As they recover, everything takes on heightened color and even the sun seems brighter.
Migraine headaches often begin with visual symptoms such as floating black specks surrounded by patches of shimmering vivid color. Fever, drugs, fatigue and hunger can affect your sight in odd ways; the object you’re looking at may suddenly shrink and recede from you. coming back into place when you centre your gaze on something else.
Although the brain is the key to seeing, our commonest visual troubles are physiological shortcomings in the eye itself. Short sight, long sight, astigmatism (where vision is distorted by irregularities in the cornea — the transparent coating of the pupil and iris) and aniseikonia (a rare condition in which the two eyes see images of different sizes) are caused by structural defects and are normally corrected with spectacles. Color blindness indicates a flaw in the retina that can't usually be remedied. Crossed eyes are due to lack of muscular and mental co-ordination between the two eyes. Presbyopia, the farsightedness of middle age, is one of the natural degenerative changes that occur as your body grows older.
Of all eye defects, myopia—short sigh! —is the most familiar and the most controversial. Is it caused by eyestrain, too much reading, inadequate diet or even some psychological difficulty? Can you prevent or cure it by exercise or throwing away your spectacles? Is the comicstrip convention that myopic people are sh\. bookish fellows based on fact or fancy? All these questions are hotly debated, although most doctors are convinced that myopia is simply an accident of overgrowth that can be corrected only with concave lenses, and probably isn't closely related to personality.
Whether you have long or short sight depends chiefly on the focal length of vour eye. According to the curvature of the lens and cornea, and the distance between the lens and the retina, light rays may focus either behind or in front of the retina, and so fail to produce the clear image that results from perfect focus. All babies are born long-sighted, and gradually develop normal sight as their eyeballs grow proportionately longer. While some eyes retain a degree of long sight, others grow too much and develop myopia. This usually begins to appear about the time a child reaches school age, increases in a series of waves through adolescence and levels off when he stops growing, l.ike extra height or big feet, an overlong eyeball is usually hereditary, and for the myopic child glasses are as necessary as new shoes.
Because the progress of myopia coincides with a child's schooling, people once thought that prolonged close work actually caused short sight. Nowadays eye specialists think it's more likely to be the other way around: the short-sighted child may turn to books because he can handle them more easily than sports. According to Dr. Arnold Gesell of the Yale Clinic of Child Development, markedly myopic children tend to concentrate on close-up activities and often show an early aptitude for talking, reading and memorization.
Can you see blue and yellow?
It has sometimes been suggested that exercising your eyes can cure short sight. While doctors concede that you can train yourself to be more observant, they point out that you can’t change the focal length of your eye by relaxation, concentration or exercise. Sir W. Stewart Duke-Elder, whose Text Book of Ophthalmology is considered the final authority, says: "Apart from the optical correction no specific treatment for simple myopia is indicated. The extent to which spectacles are worn, the amount of near work done, peculiarities of diet or the administration of drugs are immaterial, provided that hygienic conditions are good, overstrain is avoided and the general standards of health and development are maintained.”
Since no one has fully solved the mystery of how we see color, there’s no treatment for the most common form of color blindness, which permanently impairs your ability to see red and green. Like hemophilia, this defect is carried from grandfather to grandson through a mother with normal vision. A rarer kind, affecting blue and yellow vision, is sometimes the result of a disturbance in body chemistry, such as tobacco-alcohol poisoning, and may be only temporary. So few situations call for accurate color vision that many color-blind men aren't aware of their handicap until they arc checked for some specialized occupation such as (lying.
Not long ago a Toronto optometrist had to tell a seventeen-year-old patient the disappointing news that he had wasted months training for a job he could never fill. Wanting his son to master a technical skill, the hoy's father had sent him through a course in electronics. He was on the point of being hired by an electrical company at a higher salary than his father had ever made in his life, when a medical examination revealed unsuspected color-vision defects that ruled him out of electronics altogether because he couldn’t match complicated wiring diagrams.
Even for people with perfect sight, color is deceptive. Though a child paints things in stark solid colors—a red car, a yellow house—a grown painter learns that shadows and reflections break every surface into dozens of different shades. I he apparent color of any object depends partly on the colors of its surroundings and on the colors the eye has seen a moment earlier. For instance, a patch of light with the spectral distribution of noon sunlight looks blue when it’s surrounded by yellow, and pink when it’s placed on a field of green. In daylight, red and yellow seem the brightest colors of the spectrum, but in dusk blue and green look brighter. East year a Japanese researcher found that an object looked larger than its real size when it was painted orange, yellow or white, and smaller when painted blue or black—-confirming the wisdom of fashion advisers who tell fat women to wear dark dresses.
Unlike color blindness, crossed eyes can usually be cured with corrective lenses, visual training and sometimes surgery — if they're caught early. Since a child who squints is unable to fuse his two eye images, he involuntarily suppresses the weaker eye to avoid seeing double. If this happens during the years when his sight is still developing, up to the age of six or seven, the unused eye and its corresponding brain areas will never learn to see.
Surgery is the only way of treating cataract, a form of blindness that occurs when age. disease, injury or diet deficiency interferes with the nutrition of the lens, causing it gradually to cloud over and
prevent light from reaching the retina. Diabetes, for instance, sometimes causes cataract by throwing out of balance the proportion of blood sugar and protein in the lens and the fluids that surround it. To restore sight, the surgeon removes the clouded lens and its surrounding capsule. Some ophthalmologists use a recently developed operation that replaces the natural lens with a plastic substitute.
z\ more serious cause of blindness is glaucoma, a hardening of the eyeball that happens when the natural drainage of its interior fluid is interfered with in a way not yet fully understood. Because the pressure that builds up progressively damages the retina and optic nerve, the only defense against glaucoma is early diagnosis and operation or treatment with drugs such as Diamox, a new sulfa derivative that slows down the production of fluid within the eye.
Watching TV can be good
Although severe forms of blindness are comparatively rare, we all suffer some loss of sight as we grow older. After thirty, our pupils shrink, reducing our ahility to see in dim light, and the lens and its controlling muscles become less elastic. By fifty, the lens has lost about ninety percent of its power of accommodation. and we find ourselves unable to focus on fine detail at less than arm’s length without glasses. At the same time the retina and optic nerve begin to degenerate, the cornea becomes less transparent and the iris fades.
But in children eye care can preserve and improve sight. To develop a child’s sight to its fullest you should encourage him to use his eyes in every possible way.
Reading, watching television, educational toys and fast-moving outdoor games all help as long as his eyes get plenty of light and variety and aren't restricted to one kind of use. When he spreads the comic page on the floor and sprawls with his nose a few inches from the paper, he may only be showing that the lens of his eye is in fine shape.
Early tests for distance, depth and muscular co-ordination will pick up defects that should be corrected right away, to help him adjust to school work and social life as well as to protect his eyes. Psychologists say that a child who can't see properly soon loses interest in his work and feels inferior because he can’t keep up with his classmates. A cross-eyed child may soon become shy and self-conscious about his appearance.
Your eyes are so sensitive and so closely linked with your whole mind and body that they respond to physical or emotional stress like a barometer. Because fatigue, anxiety, sickness, heavy drinking and poor diet keep them from working properly, the best way to protect them is to keep healthy.
Sight is vital because we live in a visual civilization, where practically all our actions are controlled by our eyes. We use them for everything from watching television to driving at high speeds, and for ceaselessly learning more and more about ourselves and the rest of the world. They provide the key to the written tradition that tells us all we know of the past, and help us to cope with developments that will shape our future. And because everyone looks through his own private window, depending on the workings of his mind, our eyes make each of us a little different from anyone else. ★