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Daltonism is a state which develops at the person owing to lack of cells of a retina which are sensitive to color, or because of failure in their work. A retina is called the layer of the nerves located in back part of an eye. These nerves are responsible for transformation of light to nervous signals which, in turn, send information to a brain. At those who have daltonism rejection of some flowers is shown. As a rule, it is red, blue, green colors or their various combinations. The disease received the name by name the English research of John Dalton who described a certain type of color-blindness in 1794, being guided by the feelings. Dalton did not distinguish red color, also two his brothers had a similar disease. However, the scientist understood that he does not see red color only when he already was twenty six years old.
As a rule, an eye possesses three types of conical cells (conical flasks). They are located in a retina and are sensitive to light. Each of three types sensitive to a certain color — red, blue, green. Respectively, the person distinguishes colors, its conical cells define quantity of cells of three called primary colors. If one or more these types of cells are absent, or they work incorrectly, then the person does not see a certain color in general or distinguishes it in the changed look.
Generally conical cells concentrate on the center of a retina, providing, thus, bright color sight. These cells most qualitatively work at good lighting therefore at dim light distinguishing of flowers significantly is at a loss.
It is also accepted to call daltonism "a color problem of sight ", most of people for whom daltonism is diagnosed, nevertheless partially distinguish color scale. However many people with daltonism cannot distinguish colors at all.
And, respectively, the person has sight problems which, anyway, connected with perception of flowers, generally are genetic since the birth. At the same time problems with sight of other character are provoked by aging of the person, his illness, injury of eyes, and also collateral influence of some medicines. The problems of sight of hereditary character concerning determination of color are more frequent, than the diseases acquired. More often they are shown at males.
Diagnosis of daltonism
To diagnose this disease, specially developed tests for daltonism are applied. Today the most famous test for daltonism is a pseudo-isochromatic test of a plate. The essence of the test consists that to the patient suggest to look at set of points of certain flowers and to consider what letter or number are designated there. On what samples of people perceives or does not perceive, it is simple to specialist to define what type of a problem of color sight takes place at the patient. In the course of the test use several different plates.
For those at whom the acquired problems of color sight are assumed, it is offered to pass a test for daltonism which is based on distribution of objects of color. Distribution of different objects is involved in the test, considering their color or a shade. The patients having daltonism will not be able to pass this test, having correctly spread out all color plates.
Similar problems directly change the general quality of human life. The wrong perception of flowers not only influence process of training, reading, but also afterwards narrow possibilities of the professional choice of the person. But at the correct approach both children, and adult patients can compensate own impossibility to distinguish some colors.
During time symptoms of daltonism can change. So, different people can see various shades of flowers. People with daltonism do not distinguish red, green and blue colors at all. Those who have problems less serious can see blue or yellow colors. At the most serious disorders of color sight people are not capable to distinguish colors at all. They see the world only in white and black tones, with various shades of gray color.
Problems with sight of hereditary character are characteristic at the same time of both eyes. At the same time the acquired problems of this character can be shown only in one eye. Also they can mention one eye stronger, than another.
The inherited pathologies of color sight generally take place already at the birth, and over time they do not change at all. And here the acquired problems can change or be aggravated throughout a long time, with age or owing to a certain disease.
Types of hereditary daltonism
The most widespread problems with sight of hereditary character is sight pathology at which the person does not distinguish or hard distinguishes red or green colors. Similar visual impairments take place approximately at 8% of men and at much smaller — 1% — the number of women. Very seldom both at women, and at men the problem of color sight when the patient distinguishes blue and yellow shades absolutely equally is observed.
In total it is accepted to distinguish four main types of the inherited problems of color sight:
The abnormal trikhromasiya is the most eurysynusic pathology of color sight. It is observed at the people having three types of conical flasks, but at the same time one type of conical flasks is absent or has a lack of pigments for perception of flowers. Those who have similar pathology see all colors, however some — green, red and blue – they see in other shades, than the people who are not suffering from disturbance of color perception.
Dikhromasiya is a problem which is shown in the absence of one of three types of flasks of a cone. So the person sees only two colors from three main. Most of the patients suffering from a dikhromasiya has no problems with determination of distinction between blue and yellow flowers. However it is already much more difficult to define a difference between red and green color to such people. At diagnosis of a problem it is important to consider that very few patients with a dikhromasiya well distinguish red and green colors, but at the same time confuse blue and yellow colors. This type of a disease is considered more serious, than an abnormal trikhromasiya.
The blue conical monokhromasiya is pathology, two flasks of a cone are not at which — red and green. This type of a disease is shown only at males. People with similar pathology badly see at distance, also at boys at early age the involuntary movements of eyes are sometimes observed (this phenomenon is called a nystagmus). From the whole color range people with similar pathology distinguish exclusively blue color and its shades.
Achromatopsia – the last, fourth type of the inherited disturbances of color sight. In this case the person has no three types of flasks of a cone. At similar pathology of people sees only shades of black, white and gray flowers. Other diseases of sight also are rather often diagnosed for patients who suffer from this type of an illness. So, they have rather indistinct sight when reading, they badly see at distance. Also high sensitivity to lighting is shown. Similar disturbance is the most seldom found type of a color problem, but at the same time the most serious of all types. Other name of this illness — a monokhromasiya of sticks of a retina.
Practically all problems of color sight are directly connected with the genes regulating production of pigments in conical flasks. These genes which are responsible for perception with the person of red and green flowers are located in the X chromosomes. Respectively, two X women have chromosomes, and only one – at males. So, at the man the problem of perception of red and green flowers will be shown if there is a defective gene in its X chromosome. Women can have a similar gene in any of two X chromosomes. It also causes problems with perception of flowers, however it occurs much less often. Also the bearer of such gene has 50% chance to transfer this gene to sons. And here at daughters of such woman similar problems with sight can be shown only in case of inheritance of defective genes by her from both parents. Of course, the similar case is less probable.
In those families where there is a hereditary predisposition to manifestation of color problems with sight, the similar pathological phenomena can be shown even through several generations.
Genes which are responsible for a pigment of cones of a retina and for perception of blue color are not in the X chromosomes, and in not sexual chromosome which people of both floors have. Therefore the wrong perception of blue color occur both at men, and at women. But at the same time these problems of color sight are shown rather seldom generally.
The acquired daltonism
A number of different manifestations can become the reasons of the acquired problems with color sight. So, similar pathology can arise with age changes when the person has a darkening of a crystalline lens. Thereof process people hard distinguish dark blue, dark green and dark gray colors. Sometimes, that disturbance of perception of flowers is shown also owing to collateral influence of some medicines. Such diseases can be both temporary, and constants. A number of diseases of eyes which often occur at people at any age can provoke manifestation of color vision disorders. So, glaucoma, a cataract, a makula degeneration, a diabetic retinopathy can provoke development of similar problems. Recovery of quality of sight it is possible on condition of the correct treatment of the mentioned diseases. Also wounds of eyes, especially retinas can provoke similar problems. The acquired daltonism with an identical frequency arises both at men, and at women. At a similar type of daltonism of a problem can be observed in one eye, and another at the same time can well distinguish all colors and shades.
Treatment of daltonism
Unfortunately, problems with color sight of hereditary character will not respond to correction or treatment. At the same time problems of the acquired type in certain cases will respond to treatment. However in this case the disease origin is important. So, if problems with color perception arose owing to a cataract, then after its removal color sight can return to norm completely.
At people with hereditary daltonism in easy a form the resistant habit to associate a certain color with some subject and, thus, to define this or that color in everyday life is developed over time. Today to color-blind persons with some forms of a disease suggest to wear special glasses a share of correction of color perception. However they can correct perception only of some shades.
Daltonism is an obstacle for training and the subsequent work in some spheres. So, color-blind persons cannot be firemen, drivers, electricians, pilots, doctors, etc. Also the person with daltonism will not be able to get the driver's license.
Section: Diseases of eyes