Typically, something moves at the periphery of our field of vision. The eyes shift to bring whatever it is into detailed vision by projecting its image on to the centres of the retinae. The retinae then provide the data that the brain uses to decide whether the moving object is threatening, edible, sexy, inconsequential, or, if you are playing cricket, catchable.
By contracting the pupil the iris assists vision in three ways. First, it stops light from the sides of the cornea forming blurred images on the retina. Secondly, it prevents too much light from entering the eye. Thirdly, it enables depth of focus. Read the rest of this entry »
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 »
In an ideal world the best way to restore an eye to normal would be to replace the cataractous lens with a clear one of the same power lying in the position from which the original lens was removed.
At the Oxford Ophthalmological Congress the eye surgeon Harold Ridley reported the results of eight operations that he had performed to insert a Perspex lens. He thus founded a completely new branch of ophthalmic surgery. Ridley had treated many ocular injuries suffered by members of the Royal Air Force during World War II. Aircraft windshields (made of Perspex) had shattered after explosions or the impact of bullets, and Perspex fragments had penetrated the eyes of plane crews. Ridley had noticed how inert Perspex was in the eye and how little inflammation it caused. 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 greater the ophthalmologist’s knowledge of general disorders, the more help he will be in their diagnosis, or at least in making a wise referral. And this applies as much to nervous disorders as it does to diseases in the blood. The central nervous system is necessarily and intimately connected with the eye and vision, which are therefore affected by nerve and brain abnormalities. Read the rest of this entry »
Imagination is closely allied to memory, for we can imagine only as well as we remember, and in the treatment of imperfect sight the two can scarcely be separated. Vision is largely a matter of imagination and memory. And since both imagination and memory are impossible without perfect relaxation, the cultivation of these faculties not only improves the interpretation of the pictures on the retina but improves the pictures themselves. Read the rest of this entry »
This exercise trains your eyes to provide a quick, accurate, and detailed comprehension of pictorial information. The two exercises will increase your short-term visual memory.
