What are the Indications OF Eye Problem?
THE many cells which make the human eye have first correctly executed a multitudinous dance engaging millions of performers in hundreds of sequences of different steps. To picture the complexity and the precision of this performance beggars any imagery. It suggests purposive behaviour-not only by individual cells but by colonies of cells. And the impression of concerted endeavour comes, it is no exaggeration to say, with the force of a self-evident truth.
Each eyeball is a little camera. Its smallness is part of its perfection. But it is a spheroid camera which focuses on itself automatically, according to the distance of the picture. The eyeball turns itself in the direction of the view required. And it is contrived as though with forethought of self-preservation. Should danger threaten, in a trice its skin shutters close, protecting its transparent window.
Indications OF Eye Problem
What are the Indications OF Eye Problem?
The biconvex lens is made of cells like those of the skin but modified to be glass-clear. It is delicately slung with accurate centring across the path of the light which enters the eye. In front of it a circular screen controls, like the iris diaphragm of a camera, the width of the beam and is adjustable, so that in a poor light opens up to let in more of the light. The cameras of the two eyeballs are finished to one standard so that the mind can read their two pictures as one.
Not only must the lens be glass-clear but its shape must be optically right. The optician obtains glass of the desired refractive index and skilfully grinds its curvatures in accordance with mathematical formulae. With the lens of the eye, a batch of granular skin cells are told to travel from the skin, to which they strictly belong, and to settle down in the mouth of the optic cup and arrange themselves in a compact and suitable ball.
Next they are told to turn into transparent fibers, and to make themselves into a sub-sphere a lens of the right size, set at the right distance between the transparent window of the eye in front and the sensitive seeing screen of the retina behind. In short, they behave as if they are fairly possessed.
Furthermore, the lens of the eye compassing what no glass lens can, changes its curvature to focus on near objects, as well as on distant ones, when required-for instance, when we read. And not merely the lens but the pupil-the camera stop-is self- adjusting. All this without our having even to wish it; without our even knowing anything about it, beyond the fact that we are seeing satisfactorily.
What are the Indications OF Eye Problem?
The lens and screen cut the chamber of the eye into a front half and a back half, both filled with clear humour, practically water, kept under a certain pressure to maintain the eyeball’s right shape. The front chamber is completed by a layer of skin specially made to be glass-clear. The skin above and below this window grows into movable flaps, dry outside like ordinary skin, but moist inside, which wipe the window clean every minute or so by painting fresh tear water over it.
The eye’s key structure is the light-sensitive screen at the back. It receives and records a continually changing moving picture which is life-long and requires no change of “plate,” through every waking day. And it signals its shifting exposures to the brain. It is a ninefold layer of great complexity. It is, strictly speaking, a piece of the brain lying within the eyeball. The cells that are at the bottom of the cup become a photo- sensitive layer-the sensitive film of the camera.
The nerve lines connecting the photosensitive layer with the brain are not simple. The human eye has about 137,000,000 separate “seeing” elements spread out in the sheet of the retina. The number of nerve lines leading from them to the brain gradually condenses down to little over 1,000,000.
They are in series of relays, each resembling a little brain, and each so shaped and connected as to transmit duly to the right points of the brain itself each light picture momentarily formed and “taken.” On the sense-cell layer the image has, picture-like, two dimensions. But the step from this.
The mental experience is a mystery. For it is the mind which adds the third dimension when interpreting the two-dimensional picture! And it is the mind which adds colour. The chief wonder of all we have not touched on yet. The eye sends into the cell-and-fiber forest of the brain throughout the waking day continual rhythmic streams of tiny, individually evanescent electrical potentials.
These electrified shifting points in the brain bear no obvious semblance in space pattern to the tiny two-dimensional upside-down picture which the eyeball paints on the beginnings of its nerve fibers to the brain. But that little picture sets up an electrical storm.
And that electrical storm affects a whole population of brain cells. Electrical charges have in themselves not the faintest elements of the visual-have nothing of distance, nor vertical, nor horizontal, nor colour, nor bright- ness, nor shadow, nor contour, nor near, nor far, nor visual any- thing yet they conjure up all these.
The twilight zone between mind and eye has been most deeply explored by the late Adalbert Ames, who gave up a law career to become an artist. He grew enthralled with the mind: how does the mind use the eye? One phase of Ames’s work was the study of optical illusions. Princeton University in America now has a small museum full of these.
Indications OF Eye Problem A typical Ames demonstration is a room in which everything slopes: walls, ceiling, floor. But all the distortions are so calculated that, to the eye, they cancel each other out; the room looks, as you peer in through a peephole, just like a normal four-square room.
A tall man walks from one part of the room to another-and shrinks to a dwarf before your eyes. The ceiling of the room is higher in his corner than it is where you are standing, and this makes him seem shorter. What does it prove? It proves how heavily our experience influences our seeing.
The eye really sees only patches of colour and light. The mind says what that is and the mind has nothing to go on but past performance. Rooms are four-square: that has been true in your experience. When the tall man walks across the room, you are more willing to see him grow short than to see a room of such devilishly ingenious craziness.
Just looking is not enough. A little boy who touches everything he sees gets to know the world. A tourist traveling in foreign on the other hand, too often sees only his own pre- countries, conceptions. We should behave like little boys and not tourists.
How explain, then, the building and shaping of the eyeball, and the establishing of its nerve connections with the right points of the brain? And how do you explain not the eye but the “seeing” by the brain behind the eye? This is the wonder of wonders, familiar even to boredom, so much with us that we forget it all the time.
What are the Indications OF Eye Problem?