There have been many research programmes involving humans and primates aimed at finding answers to the sort of question suggested in the preceding paragraph, but generally each attempt has only uncovered a further set of factors making any final solution, any final map of the ‘genes versus environment‘ problem, less and not more likely. Perhaps in some future era when education returns to a system that doesn’t require books, but where knowledge is computer-stored and audio- retrievable, then short-sight, where it occurs, will be more easily explicable. Meanwhile we should teach our children not to hold their heads too close to the printed page, not to read for too long periods, to use good light and to develop their distance vision in outdoor pursuits. Perhaps, too, we should encourage them to develop their thought-processes, rather than seek to fill their heads with useless data as though they were merely memory banks. Read the rest of this entry »
It is known that because of inheritance not everyone will have eyes of the same size and optical power, that some eyes will fail to achieve ‘normal’ functional standards. Thus at least 15 per cent of us will have developed some degree of short-sightedness by the age of twenty-five, owing to the eye not growing in balance with the rest of the optical system seen as a whole. But this statistic applies only to post-industrial populations. The incidence of short-sightedness is much less among preindustrial peoples, and so it cannot be hereditary factors alone that are at work. The correlation is between short-sightedness and socio-industrial development, not necessarily between short-sightedness and race. There are as many short-sighted Japanese as there are short-sighted Europeans. It could be argued that where pre-industrial conditions still exist the mechanics of natural selection have ‘weeded out’ congenital short sight, but it seems much more likely that a tendency-towardsshort-sight-given-certain-conditions is inherited, and inheritable, among all peoples. Read the rest of this entry »
There are further classifications according to lens design, finish, colour, etc., which make the whole subject very confusing. If you want what is best the answer must be, ‘Whatever your practitioner advises as the best optical correction according to your eye sensitivity and required duration of wear.’ The classifications given are in fact properties of the lens, and a combination of them gives a particular kind of lens. Some types are commercially available by trade names on an `off-the-shelf’ basis, others have to be manufactured by specification. They are all made of plastics, however, though some absorb water while others do not. Most absorb and transmit gas, a necessary function to maintain the chemical equilibrium of the eye-system. Read the rest of this entry »
Where cataract is due to abnormal body metabolism, then treatment of the metabolic disorder can sometimes prevent development of cataract, or even reverse cataract where cataract has begun. Diabetes mellitus is a good example of this. Otherwise metabolic cataract can be treated by conventional methods. It should be said at once that in most countries of the world eye-drops and medicines of ill-founded clinical value, and rarely backed by any sound medical trials, are still available. Read the rest of this entry »
The retina, then, is a nerve pad dependent upon a complex network of support systems. One of these support systems is a supply of blood, for it is in the blood that many of the essential nutrients are carried from one part of the body to another. Therefore the eye, and more particularly the retina, is or can be affected by deficiencies in other organs. The retina is in fact fed by blood systems both in front and behind, and many blood diseases can have a deleterious effect on retinal functions; and both systems are sufficiently intricate and fine to be hypersensitive to abnormalities in the blood. However, since the variations and permutations of retinal degeneracy are enormous it is sometimes very difficult to diagnose its cause. It is always possible to describe what one sees as being wrong with a decayed retina, but even after many specialized tests it can still be impossible to say with any accuracy what is the precise cause. This has seriously hampered the treatment of some retinal conditions. Where the cause of a disease is known it is always much easier to prescribe a cure, or at least medication that will halt or slow down what is usually a progressive condition. Read the rest of this entry »
As we get older, all our blood vessels acquire harder walls, making it more difficult for the heart to pump blood through the whole system, especially the smaller vessels. Resistance to the flow of blood results in increased, or ‘higher’, blood pressure. The heart simply has to work harder in order to meet and overcome the developing resistance. The small vessels of the retina, or arterioles, can be examined minutely with an ophthalmoscope and changes of hardness in their walls easily seen. Because they are so small and fine they are sometimes the first to break down, so that if the blood pressure becomes very high they may leak blood and serum. When this happens the results can easily be seen on the surface of the retina between the vessels. 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 »
There is a well-known story about Noel Coward. The dramatist was out walking with two small children one day when the party came into view of two dogs engaged in the act of copulation. `Uncle Noel, what are they doing?’ cried one of the boys. ‘It’s perfectly obvious,’ replied Coward. ‘Can’t you see? The dog in front is blind, and the dog behind is pushing him to St Dunstan’s!’
The subtlety of this anecdote lies in the substitution of one taboo subject by another. Historically, blindness has carried different cultural connotations. Among the ancients it was often considered as a punishment meted out by the gods. In the best known of the Greek myths, Oedipus gouges out his own eyes in a hubristic act of self-inflicted retribution. In modern times blindness is more simply perceived as a misfortune. Read the rest of this entry »
No phase of ophthalmology, not even the problem of ac- commodation, has been the subject of so much investigation and discussion as the cause and prevention of myopia. Since hypermetropia was supposed to be due to a congenital deformation of the eyeball, and until fairly recently astigmatism was also supposed to be congenital in most cases, these conditions were not thought to call for any explanation or to admit of any prevention; but myopia appeared to be acquired. It therefore presented a problem of immense practical importance to which many eminent men devoted years of labor. Read the rest of this entry »
People whose eyes are stressed often see fleeting images. These are similar to the images on a television screen after a station has signed off: patterns and colors that move about but often appear gray and diffused. The eyes even mirror mental restlessness. You experience this as swishing images and incomplete darkness when you close your eyes.
Therefore, this exercise is a good way to measure your rental state, as well as your eyesight. When you shield tour eyes, the transition from a shimmering, gray state to leep blackness indicates the change from actively seeing o a totally relaxed, restful state. Read the rest of this entry »
