The spectacle lens that corrects short sight or myopia is a negative power: light rays from distant objects are bent in such a way that they become more, not less, divergent. The degree of divergence will depend on the power of the lens. When the degree of (artificial) divergence is equal to the degree of short sight, the eye will form a clear image on the retina. A usual degree of short sight is up to —8.00 dioptres. But in fact it is how healthy the back of the eye remains, and how thin the outer coats of the eye become, that determine the future of the shortsighted person. Read the rest of this entry »
The eye has its natural protective mechanisms. The lids, for example, protect the front of the eye from dust, wind and objects coming towards the face. They also protect the eye from excessive light. The eye itself is set in its bony cavity: the orbit. In the orbit there are some soft fatty tissues which act as a cushion, permitting the eye to sustain a light blow without injury. Nevertheless the eyes are vulnerable. The eye will be injured, often severely, by fast-flying hard objects, and also by some gases and solutions. It is easy to incapacitate a human being, either temporarily or permanently, by spraying irritant solutions onto the face, and such methods have been widely used by criminals, police and the armed services. Read the rest of this entry »
To repeat a very important principle: you cannot see anything with perfect sight unless you have seen it before. When the eye looks at an unfamiliar object it always strains more or less to see that object, and an error of refraction is always produced. When children look at unfamiliar writing or figures on the blackboard, distant maps, diagrams, or pictures, the retinoscope always shows that they are myopic, though their vision may be absolutely normal under other circumstances. The same thing happens when adults look at unfamiliar distant objects. When the eye regards a familiar object, however, the effect is quite different. Not only can it be regarded without strain, but the strain of looking at unfamiliar objects later is lessened. Read the rest of this entry »
The object of all the methods used in the treatment of imperfect sight without glasses is to secure rest or relaxation, first of the mind and then of the eyes. Rest always improves the vision. Effort always lowers it. Persons who wish to improve their vision should begin by proving these facts to themselves.
To demonstrate that strain lowers the vision, think of something disagreeable, some physical discomfort, or something seen imperfectly. When the eyes are opened, it will be found that the vision has been lowered. Read the rest of this entry »
