New Light on the Eyes - Revolutionary and scientific discoveries wich indicate extensive reform and reduction in the prescription of glasses and radical improvement in the treatment of disease such as cataract and glaucoma

R. Brooks Simpkins

• Editore: Youcanprint
• Anno: 2016
• ISBN:
  9788892635449
• Argomento: Medicina
• Categoria: Oftalmologia e optometria

Today, millions of men, women, and children, throughout the World, depend upon glasses. To the very many who ask, as did the Author thirty years ago, when he too was very shortsighted, `need such things be?' this book is of outstanding interest.
Written in simple words for the laity, who are entitled to an understanding of their eyes, this book is also of profound importance to the ophthalmic and optical professions. It solves many of the problems of why eyes, normal at birth, develop refractive errors. It also introduces methods for the prevention of Cataract and Glaucoma, as well as rational treatment of these diseases.
The universal prescription of glasses to-day is based upon an 'hundred years old' theory that astigmatism is congenital, that shortsighted eyes are permanently too long, and longsighted eyes too flat, and that all adjustments of focus for near vision depend solely upon the small natural lens inside the eye incessantly changing its curvature and strength.
In contradiction, however, the Author has proved, and depicts, with the aid of simple diagrams, that astigmatism is caused by irregular muscular tension on the pliable eyeball, and that normal eyes involuntarily lengthen to produce 'natural shortsight' for near vision, automatically return to an 'at rest' condition for distance vision, and arc mechanically capable of flattening for extreme distance vision or very longsight.
These natural processes, and their activation, are simply explained, and clearly indicate that developed irregular shapes of the eyes are capable of correction, and are not static unless so maintained by the wearing of glasses. Methods of scientific correction, evolved by the Author and named 'Oculopathy', are briefly indicated.
The Author demonstrates that irregular muscular tensions, productive of refractive errors, also largely contribute to the development of Cataract and Glaucoma.

- 1. How We See

EVEN though we cannot see without them, it is not with our eyes that we see. In the backs of our heads there are two areas of the brain called the visual centres, and it is there that we see. (Damage to this part of the brain can result in partial or total blindness though the eyes remain completely undamaged.) The eyes are end-organs of the brain; when an oculist illuminates and looks inside one's eyes with his ophthalmoscope he is in effect looking at a part of one's brain. But it was not until the time of the first world-war, when the investigation of visual defects caused by head wounds opened up a wide field of knowledge, that much began to be known about the relationship between the eyes and the brain.

We all know that we cannot see in the dark, and that we cannot see as well in twilight as we can in daylight. So it is light which activates the complicated visual mechanism inside our heads, and it is our eyes which collect the light. Our eyes are receiving stations which, with the terrific rapidity of electricity, collect and transmit to the visual centres of the brain the different wavelengths of light, which travel at the rate of 186,000 miles per second. We take light for granted as being just light, but actually light is an energy which powerfully and rapidly acts upon the two relatively small areas of the brain I have mentioned, thus bringing about the 'sense' of sight; so that all the time our eyes are open, and there is light for them to transmit to the brain, vision involuntarily and mechanically results.

We all know, too, that daylight comes from the sun, and that when the sun is setting we have twilight, and darkness once the sun is well below the horizon, unless there is a moon, the light from which is merely a reflection of the light from the sun; and that artificial light is an agent we employ when it is dark, so that we can see to move about, and continue to do many of the things we do in daylight. A flaming fire or even a burning match emits light-rays which enable us to see to some extent, while a cluster of candles, or an oil lamp, emit brighter rays which enable us to see better. Light-rays are of different wavelengths and are produced and radiated when gaseous matter undergoes combustion, at the same time producing and radiating heat of different wavelengths. Thus some forms of artificial light come from an ordinary flame, but even brighter light-rays come from an incandescence which actually is 'white heat'. In an electric light bulb there is a filament which is so thin (or such a poor conductor) that it is raised to white heat by the electricity from the power station; and we all know how hot our electric light bulbs are if we touch them when the light has been switched on for a little while.

The sun is a mass of flaming gases radiating both intense heat and intense white light. The sun is the source of all natural rays, both those which are known to us because they reach the earth, and many unknown which do not reach it. The rays from the sun are of different wavelengths. To understand a wavelength it is only necessary to throw a stone into a still pond and watch the ripples set in motion; some will not reach the banks; some will reach and overflow the banks; some will travel faster than others. These ripples are waves, and they vary in length; so, just as there are short and long waves when the surface of the pond is disturbed, so there are short and long waves of light and heat from the sun.

The rays from the sun are transmitted to us by the atmosphere which surrounds the earth. Daylight is made up of seven different wavelengths of energy working together. When these wavelengths are collected by our eyes they are separated one from another and energise the visual centres of our brains in such a way that we see seven different colours, namely violet, indigo, blue, green, yellow, orange and red. Of these wavelengths the red is the longest, and they diminish in length down to the violet, which is the shortest wavelength our sight can recognise. There are shorter rays from the sun than the violet, and longer ones than the red, but we cannot see them.

Clear glass transmits these seven different rays, called the visible rays; we see all seven of them when we look at a rainbow. The front part of our eyes, which is called the cornea, is transparent, and the light-rays pass right through it, and onwards through the pupil, and the lens behind the pupil, right inside the eye. At the back of the eye is the retina, which transmits the light-rays to the visual centres of the brain. (See Diagram 1.)

We cannot see as well in artificial light as we can in daylight. Bright daylight is the best light of all, and even perfect eyes can only see perfectly under perfect conditions. There is not a perfect form of artificial light, whether from a flame or from white-hot incandescence, and this is particularly so where it is a question of seeing colours properly.

Our eyes are quite small organs, very approximately spherical in shape, in circumference about the size of a halfpenny. Diagram 1 shows the construction of the eye. What we may call the outer wall of the eyeball is called the sclerotic, which is opaque and somewhat elastic. It will be seen from the diagram that this wall is much thicker at the back of the eye, and becomes progressively thinner until it reaches the cornea, which is the front lens of the eye.

The cornea is optically transparent, is set in the front of the sclerotic like a watch glass, and is only one millimetre in thickness. It collects the light-rays and transmits them into the eye.

Lining the inside of the sclerotic is the choroid, one of the chief functions of which is to nourish the retina, which is the inmost lining of the eyeball. In simple terms the retina may be likened to a very small egg-cup-shaped reflector; but in actual fact it contains innumerable nerve-endings. These are light receptors. Each of these nerve-endings (the precise number of them is as yet unknown) may in turn be likened to the cut end of an electric wire. These 'electric wires' are collected together into one 'cable' which passes out of the back of the eye. This `cable' is called the optic nerve.

The optic nerves are somewhat similar to two pieces of electric cable which bend about as the eyes move in all directions, upwards, downwards, inwards, and to one side or the other. At the back of the eye-sockets, on the nasal side, are two 'holes' through which the two optic nerves pass into the skull. There they meet, much as cables meet in a telephone-exchange. In this `exchange' the innumerable nerve-fibres, or `electric wires', from the retina of both eyes are sorted out, some of them going to both visual centres of the brain, some to one visual centre, and some to the other. This sorting out is all part of the processes of vision. (See Diagram 2.)

The main interior part of the eye behind the lens is filled with a jelly-like, but optically transparent, fluid, called the vitreous. The front part of the eye, in which the lens is situated just behind the pupil, contains a number of very complicated mechanical parts. To explain some of them would mean too many technicalities for the purposes of this book; but those depicted in Diagram I will suffice for a general understanding of our eyes.

In front of the vitreous, which is suitably maintained in contact with the retina, the inside of the eye behind the cornea is divided by the iris into two chambers, the anterior or front chamber, and the posterior or back chamber. These two chambers are filled with a watery and transparent fluid called the aqueous, the deficient or irregular flow of which plays an important part in the development of the diseases called senile cataract and glaucoma.

The iris is the coloured part of the eye behind the cornea, and is heavily pigmented. This pigmentation prevents light from passing into the eye, except through the pupil, and determines the colour of a person's eyes.

The iris is so intimately and wonderfully related to the sympathetic nervous system that every part and organ of our bodies is represented in its appropriate small area of the iris; illnesses we have had are recorded there, and the moment a bone is broken there is a mark made on the iris for life.

The pupil is an opening in the centre of the iris, through which light-rays enter the inner part of the eye, there to energise the nerve-endings of the retina, and so transmitted thence to the visual centres of the brain. As we all know, the pupil varies in size, sometimes dilating to allow more light rays to enter the eye, sometimes contracting till it is little larger than a pin's-head to prevent too much light entering the eye. This involuntary variation in the size of the pupil is controlled by two sets of different muscles, one set pulling the pupil wider open, and the other set closing it down, in much the same manner as we mechanically control the intensity of light entering a camera.

The aqueous flows from the posterior chamber of the front part of the eye, through the pupil, and into the anterior chamber. The crystalline lens behind the pupil is entirely dependent for its nutrition and its general health on the flow and condition of this watery fluid. The aqueous, being normally transparent, like crystal-clear water, also operates as a lens, since it fills the anterior chamber, which is behind the cornea and in front of the iris and the crystalline lens.

The crystalline lens itself is contained in an optically transparent capsule in the centre of the eye behind the pupil. This capsule is suspended by ligaments which are somewhat similar to the strings stretching a sheepskin out on a frame, pulling it in all directions. These ligaments are tightened or allowed to slacken by the action of small muscles, disposed all round the front of the inside of the eye, called the ciliary muscles. One set of these muscles is attached at one end to a spur or rim inside the eye, where the cornea is set into the front of the eyeball, and at the other end to the choroid. These muscles may be likened to a bow-string. They play a part in maintaining or changing the curvature of the front part of the pliable eyeball, and thus in maintaining or changing the curvature of the cornea and varying its strength as the first lens of the eye. The other set of ciliary muscles pulls the opposite way. Thus a balanced tension of this important part of the internal mechanism of the eyes is maintained.

At the back of the eye and in line with the pupil is a small depression in the centre of the retina called the fovea centralis. The fovea centralis is the most sensitive part of the retina and enables us to see with true visual acuity; that is, to see every outline and every detail sharply and clearly. An imaginary straight line extending the length of the eye from this small depression, through the centre of the crystalline lens and the pupil, to the centre of the cornea, is called the visual axis.

In conjunction with Diagram 1, the foregoing paragraphs afford a basic description of the structure of the eye. As I have already suggested, a camera is a less perfect, less complicated, man-made mechanism based upon this structure; and since the principles of a camera's workings will be known to many, it is perhaps instructive to pursue the parallel.

We have seen that the diaphragm of a camera has a central aperture which can be made smaller or larger to control the amount of light, particularly side rays, entering the camera, which diaphragm corresponds with the iris of the eye, while the central aperture corresponds with the pupil. The lens of the camera focuses the incoming light-rays on to the sensitive chemicals of the film or plate in much the same way as the cornea and the crystalline lens of the eye focus incoming light-rays on to the sensitive nerve-endings of the retina. When the film or plate is developed, the result is the negative from which the photograph is printed: the impulses transmitted by the nerve-endings of the retina to the visual centres of the brain give us the visual image. All the time our eyes are open, they are giving us eight 'photographs' per second of our surroundings. The cine-camera, the ordinary camera, and our eyes are all activated by the same light-rays which they collect. (The cinematograph projector contains an artificial incandescence of such intensity as to project on to a screen the details of the photographs taken by the cine-camera, and this is done at a speed which gives us the visual sense of people and things in motion.) But to obtain clear photographs the camera and the cine-camera have to be accurately focused; and even in the brightest of daylight or artificial light our eyes likewise have to be accurately focused if we are to see clearly. If they are wrongly focused, both the still camera and the tine-camera become either shortsighted or longsighted and a blurred picture results; if our eyes are wrongly focused, the result is similar. It will be easy to see by this comparison that the visual centres of our brains, on to which our eyes project what we see, may be likened roughly to photographic printing paper or the cinema screen.

Diagram 2 shows in a simple way this process of projecting on the screen of the brain everything which is apparent in the field of vision. This field of vision is very large out in the open; while one is looking at a distant church-tower, one sees at the same time the surrounding country. But the field can also be relatively small, as for instance when one concentrates one's vision on a cinema-screen within the confines of a cinema. It is the eggcup shape of the retina which enables us to see all round us, to one side and the other, and above and below, though we are concentrating on seeing only one object clearly ( in this case the church-tower). The technical term for this wonderful visual sense is 'orientation', the determining either of one's own position in space, or of the position of surrounding objects in relation to one another. Compared with the visual ability of our eyes the camera is relatively limited in its orientation. This of course is largely because its sensitised film or plate is flat, and the retina is not.

When we look at another person face to face, our right eye is opposite to his left eye, and our left eye opposite to his right. As you look at Diagram 2, imagine that you are standing behind the screen at the bottom of the diagram, but facing the two eyes looking at the screen, which for our purpose is a simple way of representing the field of vision of those two eyes; though it is also necessary to imagine that the screen is not less than thirty feet away from the eyes, since when we are using true distance vision the visual axes (represented by the dotted lines) are parallel; (we must think of these axes as merging in the distant object of vision, e.g. the church-tower, like parallel railway-lines which appear to come together at a distant point).

In optical instruments such as field-glasses, telescopes, and even ordinary magnifying-glasses, there is a central axis of focus. This is known as the principal focus, and all other objects seen at the same time are oriented round it, or seen in their different positions relative both to it and to one another. When we are looking at near objects, we turn our eyes inwards towards each other at the front, and outwards at the back, in such manner that the visual axes, if we suppose the eyes to be looking at a pencil a few inches away, will form an imaginary V point on the pencil. This is called binocular convergence. (Binocular means with two eyes together, and convergence the meeting of two or more things at a single point.)

To return, however, to Diagram 2 and our consideration of distance vision: let us imagine that the two eyes in the diagram are those of someone looking at the clock-face on the church-tower, and that the clock-face is so far away that they can only just see the time by it. This clock is represented in the screen at the bottom of the diagram as the small central area marked A. Now we know that it is light-rays which are conveying the details of the clock-face to the eyes focused on it to see the time, and in fact these details are conveyed by an almost inconceivable number of light-rays, all of which have to be brought to a pencil-point of focus on the fovea centralis in the centre of the retina at the back of the eye. ( In the dark, bundles of light rays can sometimes be seen, for instance in a cinema, when we look up, we can see the light-rays travelling over our heads from the cine-projector to the screen in front of us.)

For the sake of convenience and simplicity we may regard these bundles of an almost inconceivable number of light-rays as pencils of light, each of which 'pencils' has to be 'sharpened' to a very fine point of focus on the fovea centralis. So our man who is trying to see the time has to sharpen each pencil of light from the distant church-clock to a point so fine as to be beyond ordinary conception. This process is called refraction. Shortsight, longsight, and astigmatism are technically termed errors of refraction, since shortsighted eyes wrongly focus pencils of light rays to a point in front of the retina, and long-sighted eyes to a point behind it, so that the fovea centralis, their proper target, is missed; while astigmatical eyes wrongly focus to two different points, either in front of or behind the retina, so that the fovea centralis is again missed. We shall consider later how these errors of refraction are produced.

Since the cornea is transparent, the pencils of rays from the distant church-clock pass through it when they impinge on it. But it is also a lens, so that, as the ingoing light-rays pass through it, they are refracted or bent inwards, and converge on one another; the pencil is beginning to be sharpened. The rays are again bent inwards, and again converge as they pass through the aqueous behind the cornea, and the pencil is further sharpened. Then they pass through the pupil to the crystalline lens behind it, to be finally bent inwards or sharpened to a microscopical point of focus on the fovea centralis in the centre of the retina at the back of the eye.

Let us now, however, begin to think of light-rays not as daylight, but as pulsating electrical energy working on seven different wavelengths. We have already likened nerve-fibres to electric wires, and know that ordinary electricity from the power-station is conveyed to our houses by wires which are good conductors. We know that ordinary electricity is instantaneous in action as we switch it on: the electrical energy which is light-rays travels at the rate of 186,000 miles per second. A wavelength is the distance between the crests of two waves, and the wavelengths of light are measured in terms of so many ten-millionth parts of a millimetre, each single ten-millionth part being called an angstrom-unit. The seven wavelengths which, working together, constitute daylight measure very approximately between 4000 and 7000 angstrom-units or ten-millionth parts of a millimetre. (There are, it may be remembered, 25.4 millimetres to the inch.) These impulses of energy impinge on the front of our eyes, the cornea, at the terrific speed of 186,000 miles per second as one wave follows another.

As the daylight rays transmit the face of the distant church-clock to the eyes of the man looking at the time, the pencils of rays entering each eye are made up of the seven different wavelengths; so he sees the colours of the clock, the tower, the trees near by, the sky beyond.

Still speaking approximately, we see a light-ray wavelength measuring 4000 ten-millionth parts of a millimetre as violet, a wavelength measuring 4500 ten-millionth parts of a millimeter as indigo; a wavelength of 5000 ten-millionth parts as blue; of 5500 ten-millionth parts as green; of 5900 as yellow; of 6000 as orange; and of 6400 as red. In more technical terms, what for simplicity we have been regarding as wavelengths are properly speaking 'wavebands', and each waveband contains within it longer and shorter wavelengths. This variation of wavelengths within each waveband enables us to recognise the different shades of each of the seven different colours.

Now let us follow in Diagram 2 the track of the central pencils of daylight rays coming from the church-clock which is represented there as A in the centre of the screen. It will be remembered that the visual axes of both eyes are parallel for distance vision and that the distant 'extensions' of these visual axes come to a point on the distant church-clock like the separate railway-lines which seem to converge in the distance. Meanwhile the parallel light-rays coming from the clock-face impinge on the cornea of each eye. Transmitted thence to the two foveae centrales, and thence again to the two visual centres of the brain, the separate photographs of the clock taken by each eye are fused by these centres into one photograph.

It is important to realise that, once collected by the eyes, the light-rays have become rapidly-travelling impulses of energy, scientifically known as indirect electricity.

Light-rays from the clock are first collected by the eyes as light impulses, and in the darkness of the inside of our heads these light impulses become electrical impulses. But it is only 'electric wires' from the foveal centres of both retinae, not those from the retinae as a whole, whose messages go to both visual centres of the brain, where the details of the distant clock are at last 'seen'.

We will now consider ( still looking at Diagram 2) how it is that our eyes, as well as seeing the time by a distant church-clock, simultaneously see the church-tower and all its surroundings. In the screen which represents the field of vision, four large areas, G, R...

Indice dei contenuti

• Table of Contents
• An Autobiographical Introduction
• - 1. How We See
• - 2. How Our Eyes Work
• - 3. How our Eyes Focus
• - 4. Glasses
• - 5. Cataract and Glaucoma
• - 6. Visible Ray Therapy of the Eyes
• - 7. Some Notes on oculopathy
• Suggested readings