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 »
Increasing consumption of green, leafy vegetables, in particular spinach and kale, may decrease the risk of developing age- related macular degeneration.’ A possibly lower risk for macular degeneration was also suggested among people who had a higher intake of foods containing vitamin C. Read the rest of this entry »
Macular degeneration is the deterioration of a portion of the retina which progressively impairs the central field of vision. It can drastically diminish vision, but will not result in complete vision loss since peripheral vision is not affected. 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 »
It’s wise to wear a quality pair of tinted glasses (sunglasses) that block ultraviolet light on bright days when we are spending time outside in the sun. Read the rest of this entry »
This is a condition which causes gradual deterioration of the sight mechanism from a developing opacity in the crystalline lens of the eye. The problem generally occurs after middle age, but may occur earlier in diabetics or from the use of particular medical drugs. Read the rest of this entry »
The human eye also belongs to a relatively small group that is equipped to identify different colours. Most insects, fish, birds and many animals can only distinguish different shades and textures. The basis of colour sense is the mixture of three transparent colours — red, green and blue. When they are combined in the correct intensities they make up white. People with a well-developed colour sense can recognize many hues of the same colour, perhaps even as many as a hundred. But colour sense is highly variable, and it is estimated that one male in eight is `colour-blind‘; that is to say, 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 »
In order to maintain its transparency the lens, a living structure, requires nourishment and metabolic activity. Any agency which disturbs the normal metabolism of the lens will cause a greater or lesser opacification, which is by definition a cataract. Nourishment is provided by the aqueous humour in which the lens lies, the necessary substances passing through the outer capsular membrane to reach the cells within. There are no blood vessels in the lens. Most of it consists of a form of protein, rather like egg-white, which does not occur elsewhere in the human body. Lens protein in different animals is exactly the same. This curiosity, which is called organ specificity rather than species specificity, means that if someone becomes allergic to any animal’s lens, he will also become allergic to his own. Read the rest of this entry »
Symptoms
All the symptoms of cataract are visual, the usual complaint being of a general mistiness of sight, more particularly for distance vision, as reading is often unaffected in the earlier stages. One eye is frequently worse than its fellow, but sooner or later both eyes alter. At this stage dazzle may be a cause of great distress. In normal lighting conditions vision may not be seriously disturbed, but in bright sunlight it becomes obscured by dazzle in the same way that a dirty windscreen becomes almost opaque in the headlights of oncoming cars. In this situation patients may be greatly helped by wearing a brimmed hat or tennis shade. Tinted glasses are of limited assistance because it is the direction of the light as much as its brilliance that causes the trouble. Read the rest of this entry »
