As regards lens-implant surgery the benefits are very great. To be able to have normal sight again without the need for thick spectacles or the bother of wearing contact lenses is surely the preferred treatment. Where contact lenses are used subsequent to a cataract operation, they differ from ordinary contact lenses in certain ways. The condition of an eye that has had its crystalline lens removed is known as aphakia, and aphakia almost invariably demands a contact lens that is much thicker in its centre than the lens worn by the ordinary short-sighted person. Read the rest of this entry »
A plastic lens placed in the eye where the original crystalline lens used to be seems the ideal method of correcting the vision of a patient who has undergone cataract removal. Normally the crystalline lens has an optic power of nearly 20 dioptres, equal to a strong magnifying glass, and obviously an eye of normal size requires this power to be replaced. An implanted artificial lens is one way to achieve the necessary correction. It is wrong, however, to suppose that once the operation has been performed the patient will be able to see clearly immediately. This can only occur if the implant has been expertly placed in the eye, and if the right adjustments to the optic power, using spectacles, have been made. It is sometimes necessary to perform a second, less difficult operation after a few weeks have gone by. Read the rest of this entry »
Basically, good and bad characteristics, healthy and unhealthy trends, are divided into dominant and recessive. Those that are dominant are handed down and show in the offspring; those that are recessive are handed down but do not show. Further, dominance and recession are often linked to the sex of the individual. Thus we talk about traits that are ‘dominant in females’, ‘dominant in males’, ‘recessive in females’, and ‘recessive in males’.
Suppose, for example, that both parents had a recessive trait `A’. If they had nine children the chances are that only three of them would be marked by ‘A’. But if they had only two children, the chances of either of their offspring showing trait ‘A’ are small indeed, whether the trait is for weak legs or musical genius. But if both parents had dominants of a certain trait, this would almost certainly come out in the offspring. 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 »
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 »
