When the doctor told you that you needed bifocals, you may have protested (verbally or only mentally) that you weren’t that old. Actually, you probably weren’t, even though a few grey hairs may have started to show up here and there. The average person begins to need bifocals in their 40s, and then only if he or she does reading or close work. Five hundred years ago when most people where illiterate and/or occupied with farming, bifocals were not necessary. (The life span was much shorter, too.) Today, they are almost indispensable. Read the rest of this entry »
When you get glasses for the first time, or when there is a change in your prescription, it will upset your visual world. Certainly you can expect clearer sight and more comfortable vision, but along with that you will notice some strange side effects. Objects may appear larger or smaller, closer or farther, and familiar shapes may be deformed. Don’t hit the panic button. These effects are only temporary and within a few days you should be completely unaware of them. But why the problem in the first place? There are several reasons. Read the rest of this entry »
Since most of the organs of the body are paired, you might have taken your two eyes for granted. If you stop to think about possible reasons, you might decide that with two eyes you can get a wider field of view to the sides. True enough. But to have a really terrific field of view, wouldn’t you design the system to have one eye mounted on a finger-like stalk atop your head to see all around? Wouldn’t it be nice to have the ability to see behind your back? The way it is now, there has to be a elaborate neck joint complex so that you can turn your head to get a reasonable near-360 degree panorama. Yet, nature evolved into our present set-up. Why? Read the rest of this entry »
How long has the doctor been in practice?
If you have a choice, pick someone with more experience. Read the rest of this entry »
The colour of your eyes is inherited. The colour and pattern of the iris are as individuated as fingerprints. It is coated on its back with brown-black pigment. This prevents light penetrating to the back of the eye except through its centre, or pupil. This hole can change its size, dilating or contracting as the level of light requires. In bright light, or when we wish to scrutinize a near object, it contracts. In dull light, or when we wish to relax our eyes and stare in the distance, it dilates. It also becomes bigger if we are frightened or excited, and it dilates in death. Read the rest of this entry »
It would seem appropriate, therefore, to regard the whole visual system at birth as a more or less ready-to-use computer that has not yet been programmed. The actual programming takes place soon after birth; but just when this happens is not the same with all living beings. Once the programme has been supplied it remains built-in for life; but to function well it requires frequent use, especially in the early years. Read the rest of this entry »
When light rays from a distant object pass through the cornea only the central rays are likely to form an image on the central and most sensitive part of the retina. Only the central part of the cornea (an inner diameter of between 3 and 5 mm) is sufficiently curved to bend the light-rays regularly. The light entering the more peripheral parts of the cornea only stimulate the more peripheral parts of the retina. These are bent irregularly and do not form a clear central retinal image. This ‘peripheral vision‘ is most useful for locating objects in space, and, by a reflex nerve stimulation, regulating the size of the pupil. Read the rest of this entry »
The immediate appeal of contact lenses is social. The desire of spectacle wearers to be ‘normal’, to appear in public without a facial contraption, is very real. In the USA, Europe and Japan most young short-sighted people have, by the age of twenty-five, at least tried contact lenses if their vision requires the daily or continual use of spectacles. Some patients will even persist through considerable discomfort in order to achieve ‘normalization’. And as more and more people adopt contact lenses, it becomes less and less normal to wear glasses. It is as well therefore that, apart from its cosmetic advantages, the contact lens also has some optical advantages. Read the rest of this entry »
At one time almost all intraocular surgery was performed under a local anaesthetic. For two reasons local anaesthesia is used much less commonly today. First, the whole science of general anaesthesia has greatly advanced and the likelihood of coughing has been considerably reduced. Second, methods of repairing the cataract wound are now better than they used to be. Coughing and sneezing after the operation consequently constitute less of a threat than formerly. Read the rest of this entry »
These then are the common errors of vision which may cause eye-strain. They are short- and long-sightedness, near-vision deficiency and astigmatism. Most commonly astigmatism is present with one of the other three conditions. They may all be measured by both objective and subjective methods. Objective measurement means the use of instruments, while subjective measurement requires you to state an opinion. In ordinary practice the practitioner will use both methods, and thereby establish a pattern which enables him to prescribe the right optical correction. If you repeatedly give a wrong answer to a subjective inquiry the experienced occulist will proceed to further objective (optometrical) tests. Read the rest of this entry »
