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 »
In modern times we have learned to manufacture glass of a much higher and controllable refractive capacity. Correct refraction is as important as the shape of the lens for the efficacy of an optical aid.
The grinding and polishing of regular curvatures on to transparent media to produce lenses that minify objects has thus been going on for several hundred years but the scientific principles underlying the measurement and accurate reproduction of thin spectacle lenses belong to modern times. Read the rest of this entry »
Squint, or strabismus, is a general term used to describe any one of several conditions in which the two eyes are not properly co-ordinated. One eye focuses on an object, but the other eye fails to align itself to the same fixation. Most commonly the errant eye is aligned inwards (cross-eye or esotropia) or outwards (wall-eye or exotropia); less commonly it looks upwards (hypertropia) or downwards (hypotropia). Other words to describe these conditions are ‘cast’ and ‘turn’. The phrase ‘evil eye‘ has also doubtless been used in association with squint. Where a squint remains uncorrected the person who has it is often forced to adopt an unusual, even grotesque, head- posture, adding to a general impression of unsightliness. But because the squint sufferer has the potential for normal stereoscopic vision the treatment of squint is an important ophthalmic activity. 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 »
The retinae are the sensory parts of the eyes, and to all intents and purposes may be regarded as a part of the brain. At the embryonic stage the developing brain very early on grows two buds which will become the eyes. This brain tissue gradually transforms into the light-sensitive retinae, or receptor organs. In the young foetus the buds lie just below the skin surface. The forward part of the eye tissue then invaginates to form the crystal lens of the eye, while the skin forms the cornea, or front lens of the eye. Slowly each bud is extended away from the brain, until it is only attached to the brain by a stalk, or optic nerve. Read the rest of this entry »
The correct colour of frames for you is based on your season and hair colour. When buying plastic frames, choose the same colour as your hair, but one shade lighter. If you are pale or sallow-skinned, do choose plastic frames, which bring colour to your face. Autumns in particular should consider this option.
Winters and Summers, the cool seasons, should make sure that their frames — particularly brown ones — are not reddish or golden. Even tortoiseshell must be a cool brown. If you choose metal frames, they should be silver-toned. Read the rest of this entry »
The retina, or rear receptor part of the eye, consists of a layer of different kinds of cell which meet the demands of different kinds of sight: detail and outline, colour, light and dark. But these cells cannot work unless they can produce the chemicals used to react with light energy, and the chemicals that are used to transmit the light-nervous energy to the brain. These chemicals and their application are a vastly complex subject which is still being explored; but it is known that all the products needed for retinal function come, in the last analysis, from the blood supply. Read the rest of this entry »
This not always possible for people to go to a competent I physician for relief. As the method of treating eye defects presented is comparatively new, it may be impossible to find a physician in the neighborhood who understands it, and a person may not be able to afford the expense of a long journey or take the time for treatment away from home. To such persons I wish to say that it is possible for a large number of people to correct defective eyesight without the aid either of a physician or of anyone else. Read the rest of this entry »
The results of these preventive measures were disappointing. Some observers reported a slight decrease in the percentage of myopia in schools in which the prescribed reforms had been made, but on the whole the injurious effects of the educational process were not eliminated to any extent.
Further study of the subject has only added to its difficulty, while at the same time it has tended to relieve the schools of much of the responsibility ‘formerly attributed to them for the production of myopia. As the American Encyclopedia of Ophthalmology points out, “the theory that myopia is due to close work aggravated by town life and badly lighted rooms is gradually giving ground before statistics.” Read the rest of this entry »
