This rule, that we see best only that small area at which we are looking directly, out of the center of sight, has one important exception. At night, when there is a minimum of light, we do our best and clearest sensing with the outer portions of the retina. This fact was discovered centuries ago by the astronomers, who found that, when looking directly at a constellation, they could see only the brighter stars, whereas, when they looked somewhat to one side of it, they could detect other stars of smaller magnitude. In the words of the eminent French physicist, François Arago, “in order to see a very dimly lighted object, it is necessary not to look at it.” For this reason, when trying to find your way in the dark, you should not look straight ahead; for then you will not see the dimmer objects immediately in front of you. If, on the contrary, you turn your head, first to one side, then to the other, you will see what is directly in front of you “out of the corner of your eye.”
Exactly the opposite is the case where vision in the daytime, or under bright artificial illumination, is concerned. In these circumstances (and all that follows applies to vision under good illumination), one senses and sees best only that portion of the visible environment which throws its image upon the macula and fovea: images recorded by the outer portions of the retina are less distinct as to form, and less accurate as to colour, than those recorded by the minute central area.
At average reading distance from the eyes—say fourteen inches—one can easily see the whole page of a book. But the area seen with greatest clarity will be a circle of about half an inch in diameter, while the maximum degree of precision will be confined to a single letter at the centre of that circle. This single letter represents that part of the total visible environment, whose image falls, at a given moment, upon the fovea centralis; the half-inch circle, that part, whose image falls upon the macula surrounding the fovea centralis. All the rest of the printed page gets recorded by the outer portions of the retina, and is consequently sensed less clearly.
Because of the existence of this central area of clearer sensing, the mobility of attention necessarily entails a corresponding mobility of the eyes. For, as the mind shifts its attention to a given part of the regarded object, the eyes are moved automatically and unconsciously, so that the part being attended to shall be the part most clearly sensed—or, to put the matter in physiological terms, so that the light rays reflected from the part that is being attended to shall fall directly upon the macula and fovea centralis.
When this happens we are said to be sensing with central fixation. In order to sense every part of an object with central fixation, or in other words, with maximum clarity, the eye must make an enormous number of minute and rapid shifts from point to point. When it fails to shift, it fails to see all parts of the object with central fixation and therefore with maximum clarity.
Mobility, then, is the normal and natural condition of the selecting and perceiving mind; and, because of the need for central fixation, mobility is also the normal and natural condition of the sensing eye. During infancy and childhood, most people learn unconsciously to keep their eyes and mind in this condition of mobility, and to do their sensing with central fixation. But unfortunately, for any one of a great variety of reasons, the habits of proper use may be lost.
In one way or another, the conscious “I” interferes with natural and normal functioning. The result is that attention comes to be directed fixedly, instead of with a continuous easy movement from point to point, while the eyes cease to shift, and develop a stare. Mal-functioning produces mental and physical strains, which, in their turn, produce more mal-functioning. Owing to strain and mal-functioning, the sensing apparatus undergoes distortion, and errors of refraction and other undesirable physical conditions result. Vision deteriorates, and as the bad habits of use become ingrained with time, the eyes (above all, when fitted with spectacles) lose more and more of their power of self-regulation and resistance to disease.
That staring should always be accompanied by strain and an impairment of vision is not in the least surprising. For when people stare, they try to achieve the impossible; they try to see every part of a large area as clearly as every other part. But the structure of the eye is such that it cannot sense every part of the area as clearly as it senses that one small part which is being looked at with central fixation—in other words, that part whose image falls upon the macula and fovea centralis. And the nature of the mind is such that it cannot do a proper job of perceiving, unless its attention is continually shifting from point to point of the regarded object.
To stare is to ignore these necessary conditions of normal sensing and normal seeing. In his greedy anxiety to achieve his end, which is to do the greatest possible amount of good seeing in the shortest possible time, the starer neglects the only means whereby this end can be achieved. Instead, he tries to do the impossible. The results are just as bad as one would expect them to be—strain, with consequent errors of refraction and poor vision.
Occasionally, the habit of central fixation is never acquired, most often owing to diseases of the eye during infancy. In the great majority of cases, however, it is acquired, along with the other habits of normal use, and only lost at a later date—owing, generally, to the interference of the conscious “I,” whose fears and worries, whose cravings and griefs and ambitions are for ever interfering with the normal functioning of the physical organs, the nervous system and the mind. When the habit of central fixation has been lost for some time, the macula and fovea seem to lose some of their natural sensibility through disuse.
At the same time the habit of trying to sense objects equally clearly with all parts of the retina leads to an over-stimulation of some or all of the eccentric areas, which do their best to increase their sensibility in order to respond to this stimulation. Sometimes this process goes so far that a person will, so to speak, manufacture for himself a false macula somewhere on the outer edges of his retina. When this happens, he gets his clearest vision, not when looking straight in front of him, but only when the object is regarded at an angle. This sideways vision can never be anything like so clear as normal vision in the central, macular area. But owing to the macula’s loss of sensibility through disuse, and to the strength of long-established bad habits, it is the best vision that such an eye and mind can have.
In the majority of cases, however, the loss of the good habits of mobility and central fixation, and the acquisition of the bad habit of staring, or trying to see every part of a large area equally well, do not result in this extreme degree of eccentric fixation. The starer still looks straight ahead. But because he tries to see everything equally well, he reduces the sensibility of his macula and fovea and builds up an undesirable and abnormal relationship between the perceiving mind and the peripheral areas of the retina, which are now used for sensing as much as, or more than, the central areas. Eccentric fixation is diffused over the whole retina, instead of being confined, as in the extreme cases, to a false macula at one particular point.
Without central fixation and mobility there cannot be normal vision. Hence the great importance of procedures which teach the normal-sighted person how to preserve the good habits, on which (though he generally does not know it) his good sight depends, and which help the person with defective vision to overcome the bad habits, responsible for his bad sight. For those who have never learnt central fixation, and for those whose eccentric fixation is extreme, the services of a skilled and experienced teacher will probably be indispensable. The rest, if they are shown how, can do much to help themselves. It is for them that I describe the simple, but effective, techniques which follow.
CHAPTER X, Methods of Teaching the Eyes and Mind to Move
Central fixation can be taught directly, by methods which permit the pupil to experience the fact that he cannot see every part of a large area with equal clarity. Or it may be taught indirectly, by methods which build up habits of mobility—methods which compel the mind to shift its attention and the eye to shift its area of greatest sensitivity from point to point of the regarded object. Use of the direct method entails a certain danger of increasing the strains from which the pupil already suffers.
It seems best, therefore, to approach the goal
