Color vision is routinely screened during the regular examination to detect any gross color deficiencies. For occupations requiring an excellent “color sense” such as printer, art director, stage-scenery designer, cloth dyer, etc., or for the detection of an early stage of a disease, more extensive color tests are administered. One such test requires arranging a series of round, colored discs in the correct sequence of hues. The most sophisticated color test, the anomaloscope, used mostly in research, challenges the person to mix primary green and red light sources together to match a standard yellow light. Read the rest of this entry »
Health of the eye
Complications affecting the health of the eye are extremely rare, but are possible. During the early healing phase, the eye is susceptible to infection. You will be asked to follow certain instructions, including using antibiotic eyedrops. Read the rest of this entry »
Excimer laser treatment is subject to complications, but the complication rate is very low. Patients often ask if one of these complications is likely to occur to them. It is impossible to predict whether a complication will occur in any specific case. Read the rest of this entry »
As a patient you must decide: Do you want both eyes treated on the same day, or each eye on a different day? Each approach has advantages and disadvantages. Read the rest of this entry »
I must admit to really liking computers. There is no doubt about it, personal computers have made my work much faster and more efficient. I’d never be able to move back to a manual typewriter or adding machine. Read the rest of this entry »
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 »
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 »
The spectacle lens that corrects short sight or myopia is a negative power: light rays from distant objects are bent in such a way that they become more, not less, divergent. The degree of divergence will depend on the power of the lens. When the degree of (artificial) divergence is equal to the degree of short sight, the eye will form a clear image on the retina. A usual degree of short sight is up to —8.00 dioptres. But in fact it is how healthy the back of the eye remains, and how thin the outer coats of the eye become, that determine the future of the shortsighted person. 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 »
Secondly, such rays (peripheral vision) may be scattered by such scarring and cause unusual sensitivity to bright light. The cuts may also damage the very sensitive deeper layers of the cornea creating problems in later life, although the operation is too new to know whether and to what extent this is the case. The effects of cuts cannot easily be measured, while the ability of the tissue to heal totally may prejudice even the short-term benefits. The presence of a small degree of short sight may seem a great inconvenience to a young person, and he or she is often willing to take a long-term risk for the sake of an immediate improvement. Read the rest of this entry »
