By contracting the pupil the iris assists vision in three ways. First, it stops light from the sides of the cornea forming blurred images on the retina. Secondly, it prevents too much light from entering the eye. Thirdly, it enables depth of focus. As the pupil becomes smaller the need for optical accuracy in the system regresses. In fact, if the pupil shrinks to less than one millimetre in diameter the individual could see clearly without any of the `lenses’. A short-sighted person who looks through a pinhole made in a black card will be able to see things markedly better, even though he or she is not wearing glasses or contact lenses.

The sensory part of the retina is thinner than tissue paper and is almost transparent, and is backed by a layer of pigment. Both are closely applied to a third layer of blood vessels, which ‘feed’ the whole retinal system. This is called the choroid. The retina coats the back half of the eye and consists of light-sensitive cells. It is a little similar to the hemisphere of a radar scanner.

The light-sensitive, or sensory, cells are of two types, called rods and cones. Those cells shaped like rods are arranged in groups, several sharing one nerve. The cone-shaped cells, on the other hand, have individual pathways to the brain: that is, they have one nerve each. In all there are hundreds of thousands of nerves which carry electrical messages from the eye to the brain. They are bunched together at the back of the eye and taken deep inside the brain in a sort of transatlantic cable, which is called the optic nerve. Mostly the flow of information is one-way, but there are signals that travel in the opposite direction, from the brain to the retinae.

The rods and cones may be described as small chemical factories. They make molecules of pigment that are sensitive to light (rods) and sensitive to colour (cones). The rods can be sensitive to very low levels of light, and they are the receiving cells for night vision. The cones, which are chiefly situated at the centre of the retina, are equally sensitive to light, but they also distinguish colour. Because of the nerve structure the cones give a ‘one-to-one’ account of themselves to the brain and therefore provide the ‘detailed’ focus. The rods, on the other hand, because there may be several sharing one nerve fibre, give much coarser information. They tell us where we are, both by day and night, and help to keep us orientated to our environment. The cones, on the other hand, enable us to do our work. Both kinds of cell, however, function on the same broad principles. Light and colour coming into the eye trigger minute electrical discharges which are conveyed along the nerves, or relays of nerve fibre, until they reach the visual cortex at the back of the head. These tiny impulses disturb the brain’s normal electrical rhythms, and the ‘picture’ is created. (It is now possible to record the eye’s electrical discharges, which is of some diagnostic value. The electrical changes in the visual cortex of the brain can also be collected from the scalp and be used to measure vision accurately, although this method is still chiefly of research value. The functions of the retinae can be interpreted crudely, and sometimes in detail, by their electrical behaviour, which can be measured from the front of the eye or adjacent tissues.)

The ability to see clearly, therefore, is determined not only by how well the image is in focus, how good are the lenses and how clear the fluids of the eye, but also by how active are the cones and how well their impulses travel through the brain. When the messages reach the back of the brain the image is reformed in a new electrical energy pattern, and other parts of the brain interpret this as a picture. For the developing baby and child, many patterns will be seen for the first time, and memory of them stored until reinforced and eventually identified when the image is next seen again. The acquisition of visual sense is, in this respect, similar to spoken language. Everything depends upon repetition. If we do not remember the original turmoil of birth then that may well be because it only happens once.

The rods, far more numerous than the cones, work at many different levels of light intensity. Thus, when the light becomes very dim, they still manage to transmit signals back to the brain. But because they are arranged in groups they are less useful in forming pictures. They are, however, vital for visual orientation. They tell us where objects are in space, what is our immediate and distant environment. Without this system, which with two eyes can roughly locate any object in space, we would not be able to move where we want with any confidence. Not only do the rods direct the eye muscles via the brain, but, through the same route, they also co-ordinate all the limbs.

The presence of both cones and rods make the primate’s eye exceptionally sophisticated. Elsewhere in the animal kingdom the power of vision is not so well developed. Many insects (the bee is the most familiar example) have a polygonal or faceted cornea and each polygon forms a separate optical system (like a tube or tunnel) to the retinal cell at the back of the eye. Such an eye is designed to work all round the creature without movements. Hence the difficulty of swatting a fly. Whichever way you come at it, it can see you. But the actual quality of vision is nowhere near as good as ours. At best a fly’s or a bee’s acuity can only be like that of a newspaper photograph, hundreds of small dots, while we can see in superchrome. Some birds have an optical system that can change the position of the crystal lens, and some birds have a supplementary lens in a third eyelid that can be flicked across the eye when necessary in order to find small insects. But these creatures do not have binocular vision: the pictures delivered by each eye are not synthesized.

Meanwhile, as we discover how the genetic programming of our body operates, it seems more not less remarkable that the eye grows from a ball 17 mm in diameter to one 24 mm in diameter without being noticed. The cornea and crystalline lenses make the necessary changes without any disruption to `normal services’, so that the image falls consistently on the film at the back of the eye. Is there some method by which eye- growth is controlled from the nervous system in such a way that the nervous system ‘knows’ how the image is formed? In other words, if the image goes out of focus, even fractionally, does the nervous system plot the necessary realignments in all parts of the optical system so that a good picture can be swiftly restored? The alternative would be to say that the pattern of development is pre-set and will operate irrespective of any one part being out of step with the rest, that each part will grow to its required size and optical function of its own accord. While both possibilities are perfectly compatible with the diverse ways in which genetic coding operates, the second theory seems to provide a better explanation of the occurrence of visual defects, in so far as those defects are not caused by environmental factors. But as yet the genetic machinery is not fully understood; when it is, clinicians will be better able to discover ways of diagnosing early malfunctions and therefore be in a better position to suggest ways of correcting, and even preventing, them.

Counselling apart, genetic ophthalmology as a practical science belongs to the future. Abnormal developments must therefore be discussed as they occur, not as they ‘would otherwise’ occur. In general there are three areas in which optical malfunctions may take place, the three related optical components of the eye: the cornea, the crystalline lens, and the retina. Aberrations may affect any or all of these, individually or in combination. If the cornea is too steeply curved, its power will be too great and the image will fall in front of the retina, thus causing shortsightedness. This state of affairs can be theoretically corrected by reducing the length of the eye, or by moving the crystalline lens backwards, or by reducing the power of the crystalline lens in some other way (e.g. replacing it with a weaker lens). In normal circumstances it is possible to lose up to one dioptre of power by stopping reading and all other close work and by applying drugs that relax the eye for distant vision. Alternatively, if the cornea is flattened, then its power can also be reduced. This can be done in more than one way. Since the cornea is maintained in its curvature by pressure and the elasticity of its own tissues, deep cuts in its surface, allowing the tissue to expand, will cause a flatter curve to be formed. Such an operation is called Radial Keratotomy. It is relatively simple to carry out, but as it only corrects up to between three and four dioptres of myopia it is of little help to patients whose problems are more acute. However, since in most patients the scale of myopia is only between one and eight dioptres, Radial Keratotomy is of great interest.

It is not uncommon for a patient to ask his practitioner whether he would recommend surgery, almost as though such surgery was an obvious solution which the practitioner had momentarily overlooked. What are the risks? The answer is that, in the long term, we don’t know yet. The operation produces several scars on the cornea in areas away from its centre. While clear vision is not affected, in theory at least it should slightly decrease the cornea’s ability to collect light rays from its periphery.

At the Oxford Ophthalmological Congress the eye surgeon Harold Ridley reported the results of eight operations that he had performed to insert a Perspex lens. He thus founded a completely new branch of ophthalmic surgery. Ridley had treated many ocular injuries suffered by members of the Royal Air Force during World War II. Aircraft windshields (made of Perspex) had shattered after explosions or the impact of bullets, and Perspex fragments had penetrated the eyes of plane crews. Ridley had noticed how inert Perspex was in the eye and how little inflammation it caused.

None the less, lens implantation was not immediately adopted by the world’s surgeons. Complications were common in the early days, mainly because of unsophisticated surgical equipment and imperfect lens design. Only a few surgeons, mostly in Holland, Italy, and Britain, retained their interest.

The first intraocular lens was an almost exact replica of the human model. The cataract was removed by the extra- capsular method and a small lenticulus (artificial lens), of the same size and power, was inserted into the space previously occupied by the cataract. The lenticulus was made from polymethylmethacrylate (Perspex), a material much heavier than the biological lens that it replaced. Positioned as it was in the very fragile capsule just in front of the vitreous face, its weight meant that it was ill-supported. There was a strong tendency for it to dislocate because it put too great a strain on the zonular fibres.

To overcome this problem a new generation of ‘anterior chamber’ implants was designed. These lenses are placed in the fore part of the eye, in front of the iris. They are supported by a number of legs which stand on the iris itself. Although the lens is thereby more stable, it may rub against the back of the cornea. This may happen during insertion, may be caused by the lens being not precisely the right size, or may be due to the iris itself having been pushed forward. In any event, the contact between lens and cornea causes loss of corneal cells, which in turn may lead to loss of transparency.

An alternative to this type of lens is the ‘iris-supported’ lens. In this case the lens may be positioned either in front of or behind the pupil. It is held in place by a number of loops which hook the lenticulus to the iris. Although this method reduces the likelihood of the lens rubbing on the cornea, it interferes with the normal functioning of the pupil.

Another solution is to implant a posterior chamber `capsular fixated’ lens. This type of lens is the one which most closely mimics a human lens. Resembling the original Ridley lens it is, however, equipped with flexible loops attached to the lens edge. Following an extra-capsular extraction, this new lens is inserted into the capsular bag. The loops are then allowed to expand in order to hold the lens firmly in place without either distorting the pupil or endangering the cornea. The lens is held rigidly in the correct position.

The image presented to the retina by any intraocular lens is almost the size of that in the normal eye. For this reason intraocular lenses are particularly appropriate for patients who retain good vision in one eye. It is most useful for those who have had one of their eyes damaged by injury — for instance, in a road-traffic accident. Indeed, this is sometimes the only acceptable method of optical correction.

Since implanted lenses mimic normal human lenses, it might seem proper to give every patient a plastic lens. However, the long-term effects of placing plastic in the eye are unknown. It is possible that the human body’s defence mechanism will attack the implanted lens, whose plastic will then deteriorate. Moreover, if the corneal cell loss (and consequent impairment of transparency) is extensive, sight will deteriorate. If there has been previous corneal damage from another eye disease (for example, glaucoma, or a long-term inflammatory condition), the danger of further cell loss is unacceptable.

Any degeneration at the back of the eye, which might lead to a detached retina in, for instance, very shortsighted people or diabetic patients who are at risk of developing retinal complications, is considered by many surgeons to contra-indicate an implant — particularly of the iris-supported type of lens. It is necessary to dilate the pupil widely in order to examine the back of the eye satisfactorily. If an intraocular lens is present, this procedure becomes difficult, and the lens itself may be dislodged during the inspection.

Despite these complications, there is undoubtedly an important place for the intraocular lens implant. The design and manufacture of the lenses are being continuously researched. Better lens materials have been developed. Ways of making the operation itself simpler and safer are being investigated. Methods of avoiding and treating subsequent problems are being explored. In the early 1970s the popularity of the operation increased rapidly. This was due largely to the introduction of the operating microscope, the development of finer surgical instruments and suture materials, and an increasing appreciation by ophthalmic physiologists of the eye’s response to the introduction of foreign materials. Today more implant operations are being undertaken, although the practice is by no means universal.

From birth onwards the retina is very thin (less than one millimetre thick) and transparent. It consists of two layers. The outer layer is pigmented and in intimate contact with the small blood vessel layer of the choroid. The inner layer consists of the light-sensitive cells and their nerves. These nerves form connections (synapses) with a second order of nerves. Some sensory cells form a connection with only one nerve, others form a group and then synapse with one nerve. At the same time other connective cells are present, whose purposes are to support the sensory cells structurally and provide them with nutrition. Unless nutrition from the blood vessels can reach the cones and rods the retina will quickly lose its function.

The rods, disposed mainly towards the perimeters of the retina, are very good at reacting to different light levels, but are relatively poor at picking up either detail or colour. The cones, on the other hand, situated mainly in and around the centre (fovea) of the retina, are very accurate in detail and colour discrimination, and work best at high levels of light. Together, the rods and cones make up the nerve level of the retina, which lies upon the outer pigment level without being connected to it. However, nutrition certainly passes from the choroid through the pigment layer to the optic cells.

The sense of sight begins with the many thousands of cells arranged in the saucer-like hemisphere of the retina. Detailed images are momentarily printed on the retinae and then relayed down the optic nerves for co-ordination and interpretation. The retinal print is immediately blotted out, or ‘wiped’, and replaced by the next print. The brain is capable of receiving and processing many such pictures every second. In certain respects the principles are the same as for moving film. Several pictures, each slightly different, are presented to the eye and brain within a very short space of time. The brain then joins the pictures together so quickly that a sensation of perfect continuity is created. But whereas a film strip does this in a mechanical process, the retinae operate chemically. In the visual cells of the retinae the chemicals are constantly being used up and replaced. The cells are recharged again and again without the individual normally being aware of the process. In certain circumstances, however, the chemical reactions can be slowed up. Sudden exposure to very bright light, for example, can bleach all the cells, or nearly all the cells, simultaneously. Even in the healthy adult complete bleaching by very bright light can result in his being unable to see for a minute or two. The eye requires time to contract the pupil and replenish the cells with the appropriate chemicals. Snow blindness is a well-known example of this state.

As was said previously, the retina has two visual functions: first to localize the individual in the space round him, and secondly to provide him with detailed images of objects to hand. It is because of this dual purpose that the retina is twin- textured. The rods provide a large field of vision, the cones a smaller area of scrutiny. But there are still some rods towards the centre of the retina, and some cones in the outlying areas. Were it not for this, our overall sense of vision would be uncomfortably bifurcated. As it is, the system gives us a good tool for simultaneous scanning and fixation, and works very well when the two eyes are locked and synchronized together.

One of the chemicals that is the basis of seeing is called rhodopsin, another carotene. The latter is derived from vitamin A, and is particularly helpful for night vision. Thus there is some truth in the saying that eating carrots enables you to see in the dark. The rods of the retina are charged with carotene, which derives its name from the orange pigment of the root-vegetable. When the supply of this chemical in the eye has been used up, more must be made from the body’s resources. If such resources are poor, which in the case of a diet deficiency they may be, night blindness may result. The cones, too, have their own chemicals, and the superabundance and/or lack of these may account for some kinds of poor colour vision. Recent research has provided a vast amount of knowledge about colours in general and about the colour functions of individual nutrient chemicals in the eye in particular, and the relationship between the two has opened up a research field of enormous clinical and scientific interest.

The greater the ophthalmologist’s knowledge of general disorders, the more help he will be in their diagnosis, or at least in making a wise referral. And this applies as much to nervous disorders as it does to diseases in the blood. The central nervous system is necessarily and intimately connected with the eye and vision, which are therefore affected by nerve and brain abnormalities. The most puzzling disorders, however, are those associated with psychosomatic and psychoneurotic conditions. While there may appear to be nothing wrong with the central nervous system, some symptoms characteristic of nervous disorders present themselves in patients who have a psychiatric history. To what extent can an abnormal personality affect the functions of otherwise normal tissues? If a doctor believes that this can happen to a significant degree, then any understanding of the signs and symptoms becomes very difficult. The ophthalmologist is also hampered by the technical limitations on measuring abnormality in the eye. He has to decide which technical means to use and, where there is a psychiatric overlay, they may very well render no positive results at all. Indeed, the tests themselves may induce introspective attitudes to the eye and vision not previously present in the patient. It can therefore become a question of when patients who continually present themselves with a symptom that seems to have no pathological basis deserve an expensive and sometimes hazardous investigation. To make a decision of this nature the experienced ophthalmologist must sometimes use non-clinical criteria in his judgment.

Tumors

Growths around the eyes, lids, tear glands and drainage apparatus, even in the eye, are very rare. Mostly they are non-malignant, and require only cosmetic treatment. In other words they can be masked by cosmetics, or just cut out. In general, once diagnosis is established, small lumps and bumps are watched, measured and photographed. Today the eye- surgeon is not likely to remove a whole eye simply on grounds of suspicion. Small cysts and pigmentary moles on the lids are watched or removed surgically. Cysts in the lid tissue itself, which press against the eye and disturb the vision, are generally removed by making an incision on the inside of the lid. The most common type is called a Meibomian cyst, or chalazion. This is a non-malignant growth or degeneration of a gland inside the lid. There are almost sixty such glands, and the removal of one of them is possibly the commonest form of eye surgery.

However, although the eye itself is little affected by malignant tumors, serious disorders in the brain, or in and about the optic nerve, will produce visual symptoms. Indeed, tumors on the brain, strokes and various forms of brain injury, can often be located by plotting an abnormality in the visual fields. In the past this was often the only way a brain surgeon had of knowing where to operate, but with modern X-ray brain-scan methods, diagnosis of brain disease by ophthalmology has become only a complementary measure.

Imagination is closely allied to memory, for we can imagine only as well as we remember, and in the treatment of imperfect sight the two can scarcely be separated. Vision is largely a matter of imagination and memory. And since both imagination and memory are impossible without perfect relaxation, the cultivation of these faculties not only improves the interpretation of the pictures on the retina but improves the pictures themselves. When you imagine that you see a letter on the test card you actually do see it, because it is impossible to relax and imagine the letter perfectly and at the same time strain and see it imperfectly.

The following method of using the imagination has produced quick results in many cases. Look at the largest letter on the test card at the near-point, and you will usually be able to observe that a small area, about an inch square, appears blacker than the rest, and that when the part of the letter seen worst is covered, part of the exposed area seems blacker than the remainder. When the part seen worst is again covered, the area of maximum blackness is still further reduced. When the part seen best has been reduced to about the size of a letter on the bottom line, imagine that such a letter occupies this area and is blacker than the rest of the letter. Then look at a letter on the bottom line and imagine that it is blacker than the largest letter. If you can do this, you will at once become able to see the letters on the bottom line.

Eye Flashing or Blinking

Since it is effort that spoils the sight, many persons with imperfect sight are able, after a period of rest, to look at an object for a fraction of a second. If the eyes are closed before the habit of strain reasserts itself, permanent relaxation is sometimes very quickly obtained. This practice I have called “flashing” or “blinking,” and many persons are helped by it who are unable to improve their sight by other means. Rest the eyes for a few minutes by closing them or palming, and then regard for a fraction of a second a letter on the test card, or a letter of fine print if the trouble is with near vision. Close the eyes immediately and repeat the process.

Eye Central Fixation

When the vision is normal the eye sees one part of everything it looks at best and every other part worse in proportion as it is removed from the point of maximum vision. When the vision is imperfect it is invariably found that the eye is trying to see a considerable part of its field of vision equally well at one time. This is a great strain upon the eye and mind, as anyone whose sight is approximately normal can demonstrate by trying to see an appreciable area all alike at one time. At the near-point the attempt to see an area even a quarter of an inch in diameter in this way will produce discomfort and pain. Anything which rests the eye tends to restore the normal power of central fixation. It can also be regained by conscious practice, and this is sometimes the quickest and easiest way to improve the sight.

When you become conscious of seeing one part of your field of vision better than the rest, it usually becomes possible to reduce the area seen best. If you look from the bottom to the top of the big C on a test card and see the part not directly regarded worse than the part fixed, you may become able to do the same with the next line of letters, and thus you may become able to go down the card until you can look from the top to the bottom of the letters on the bottom line and see the part not directly regarded worse. In that case you will be able to read the letters.

Since small objects cannot be seen without central fixation, the reading of fine print, when it can be done, is one of the best of visual exercises, and the dimmer the light in which it can be read, and the closer to the eye it can be held, the better it is for you.

Eyecare and Sun Treatment

Sunlight is as necessary to normal eyes as is rest and relaxation. If it is possible, start the day by exposing the closed eyes to the sun. Just a few minutes at a time will help. Get accustomed to the strong light of the sun by letting it shine on your closed eyelids. It is good to move the head slightly from side to side while doing this, in order to prevent straining. When you have become used to the strong light, raise the upper lid of one eye and look downward as the sun shines on the sclera. Blink when the desire to comes, or when you lose the power of relaxation. One cannot get too much sun treatment.

How to Practice Eye Vision with the Test Card

Place the card permanently on the wall in a good light.

Place yourself from ten to twenty feet from the card and read as far as you can without effort or strain. Over each line of letters are small figures indicating distance. Over the big C at the top is the figure zoo. The big C, therefore, should be read at a distance of two hundred feet if the vision is normal.

Now let us say you can only read as far as the fifth line at the distance indicated. Notice that the last letter on that line is an R. Now palm your eyes and remember the R. If you will remember that the left side is straight, the right side partly curved, and the bottom open, you will get a good mental picture of the R with your eyes closed. This mental picture will help you to see the letter directly underneath the R, which is a T. Use the same method at whichever line the vision seems to fail: notice the last letter of the last line you can read, palm, get a good mental picture of the last letter seen, and you will find it easier to see the one directly beneath it.

Now if you stare at the final letter, you will notice that all the letters on that line begin to blur. It is beneficial to close your eyes quickly after you see the final letter, open them, and shift to the first figure on that line. Then close your eyes and remember the first figure. You will become able to read all the letters on that line by closing your eyes for each letter.

It takes only a minute to test the sight with the card. If you spend five minutes in the morning practicing with the card, it will be a great help during the day. Also keep a record of each test in order to note your progress from day to day. Record the vision in the form of a fraction, with the distance at which the letter is read as the numerator and the distance at which it ought to be read as the denominator. For example, 20/ 20 is normal, 10/20 less than normal, and 25/2o be^tter than normal.

This exercise trains your eyes to provide a quick, accurate, and detailed comprehension of pictorial information. The two exercises will increase your short-term visual memory.

Exercise 1

• Take your time, relax, and look at the photo.
• Close your eyes and try to imagine the picture with your inner eye. Let your imagination color the photo like a picture in a child’s coloring book.
• Open your eyes and take a look at the landscape photo again. Which of the details did you remember? Which colors?

Exercise 2

• Hold the photo in front of you and close your eyes.
• Quickly open your eyes for a fraction of a second, as if taking a photo.
• Imagine that your brain is developing the picture you just took of the photo. With your eyes closed, imagine it developing. Watch how the contours slowly became clearer and sharper. Take your time. Then, look at the finished picture in your mind.
• Recommended time: one to two minutes.

Exercise 3

• Take your time and look at the photo.
• Close your eyes.
• In your mind, place yourself into the landscape.
• Listen to the sounds around you. Smell the fragrance in the air and take a walk through the setting.
• Imagine what the environment looks like past the edges of the photo. Immerse yourself in that part of the landscape.
• Try to find a beautiful place that invites you to linger for a while. Enjoy your stay in this place.
• Now, turn your attention to the real world again. Open your eyes and stretch your limbs as if you just woke u from a nap. Take another look at the photo to see how your imagination has expanded it.

Look to the left and inhale. Hold the tension in the muscles of your eyes and count to three. Exhale. Look straight ahead again. Take a deep breath and relax.

Exercise 2

Look to your right and inhale. Hold the tension in your eye muscles and count to three. Exhale. Look straight ahead again. Take a deep breath and relax.

Exercise 3

Look at the ceiling and inhale. Hold the tension in your eye muscles and count to three. Exhale. Look straight ahead again. Take a deep breath and relax.

Exercise 4

Look down and inhale. Hold the tension in the eye muscles and count to three. Exhale. Look straight ahead again. Take a deep breath and relax.

Exercise 5

Turn your head to the left, look over your left shoulder, and inhale. Hold the tension in the eye muscles and count to three. Exhale. Turn your head and look straight ahead again. Take a deep breath and relax.

Exercise 6

Turn your head to the right, look over your right shoulder, and inhale. Hold the tension in the eye muscles and count to three. Exhale. Turn your head and look straight ahead. Take a deep breath and relax.

Exercise 7

Fold your fingers behind your head. Push your head down, but continue to look straight ahead and inhale. Hold the tension in the eye muscles and count to three. Exhale. Raise your head again, look straight ahead, and relax completely.

Exercise 8

Rest your head on your fist_. with your chin pushing into the fist. Look straight ahead and inhale. Hold the tension in the eye muscles and count to three. Exhale. Take a deep breath and relax the neck and the whole body.

Exercise 9

Move your eyes to the left for as long as it takes for three breaths. Quickly close your eyes, relax, and take a deep breath.

Exercise 10

For the length of three breaths, move your eyes to the right. Close your eyes, relax, and take a deep breath.

Exercise 11

For the length of three breaths, use your eyes to trace a huge vertical figure eight on the opposite wall. Close your eyes for a moment, take a deep breath, and relax.

Exercise 12

Raise your arms and push both hands to the sides three times. With your eyes unfocused, look between your hands. Close your eyes, take a deep breath, and relax.

Exercise 13

Cover your right eye with your right hand and place your left thumb in front of your face, about 16 inches (40 cm) from the tip of your nose. Look towards the horizon, at your thumb, at the tip of your nose, at your thumb again, and finally at the horizon. Close your eyes, take a deep, long breath, and relax.

Exercise 14

Cover your left eye with your left hand. Hold your right thumb 16 inches (40 cm) from the tip of your nose. Look towards the horizon, at your thumb, at the tip of your nose, back to your thumb, and then towards the horizon again. Close your eyes, take a deep breath, and relax.

Exercise 15

Hold one thumb 8 inches (20 cm) from your face, the other 16 inches (40 cm) away. Both should be on the same level. For three breaths, look at the thumb closer to you. Become aware of two images of the thumb in the background. Close your eyes, take a deep breath, and relax.

Exercise 16

Place your thumbs in the same position as in exercise 15, but focus on the thumb farther away from you for three breaths. Become aware of the image of a frame in front of you. Close your eyes, take a deep breath, and relax.

Exercise 17

Yawn loudly and heartily three times.

Exercise 18

For the length of three breaths, move your lids very fast, like the wings of a humming bird.

Exercise 19

• Let your eyes wander.
• For the length of three breaths, enjoy the contrast of light and shadow.
• For the length of three breaths, enjoy the variety of color around you.
• For the length of three breaths, observe the different shapes around you.
• For the length of three breaths, become aware of the different movements in your field of vision.
• For the length of three breaths, expand your field of vision.

Exercise 20

Gently stroke your eyes and the area around them for the length of three deep, relaxed breaths. Cover your eyes with both hands and bathe them in darkness.