Daltonism is congenital, the acquired sight pathology which is characterized by abnormal color perception is more rare. The clinical symptomatology depends on a disease form. Patients in different degree lose ability to distinguish one or several flowers. Diagnosis of a color blindness is carried out by means of Ishikhar's test, FALANT test, an anomaloskopiya and polychromatic tables of Rabkin. Specific methods of treatment it is not developed. Symptomatic therapy is based on use of points with special filters and contact lenses for correction of daltonism. Alternative option is application of special software and cybernetic devices for work with color images.
Daltonism, or color blindness is a disease at which perception of color is broken by the receptor device of a retina at preservation of normal indicators of other functions of an organ of vision. The disease was called in honor of the English chemist J. Dalton who suffered from a hereditary form of this illness and described it in the works in 1794. Pathology is most widespread among males (2-8%), occurs only at 0,4% of women. According to statistical data, prevalence of a deyteranomaliya at men makes 6%, protanomaliya – 1%, tritanomaliya – less than 1%. The most rare form of a color blindness is achromatopsia which meets frequency of 1:35000. It is proved that the risk of its development increases in a case of closely related marriages. A large number of kinship married couples among inhabitants of the island Pingelape served in Micronesia as the emergence reason of "the society which is not distinguishing color".
Etiologichesky factor of daltonism is violation of color perception receptors of the central part of a retina. Normal at the person allocate three types of flasks which contain a tsvetochuvstvitelny pigment of the proteinaceous nature. Each of types of receptors is responsible for perceptions of a certain color. The maintenance of the pigments capable to react to all ranges of green, red and blue color provides normal color sight.
The hereditary form of a disease is caused by the H-chromosome mutation. It explains the fact that daltonism meets more often at men whose mothers are conductors of a pathological gene. Daltonism at women can be observed only on condition of presence of a disease at the father while mother is the carrier of a defective gene. By means of mapping of a genome it was succeeded to establish that mutations more than in 19 various chromosomes can become a cause of illness, and also reveal about 56 genes connected with development of a color blindness. Also daltonism can be caused by congenital pathologies: dystrophy of flasks, amavrozy Lebera, pigmentary retinit.
The acquired form of a disease is connected with the damage of an occipital share of a brain arising at a trauma, good-quality or malignant new growths, a stroke, a postkommotsionny syndrome or a retina degeneration, influence of ultra-violet radiation. The color blindness can act as one of symptoms of an age makulodistrofiya, Parkinson's disease, cataract or diabetic retinopathy. Temporary loss of ability to distinguish colors can be caused by poisoning or intoxication.
The main symptom of daltonism – inability to distinguish this or that color. Clinical forms of a disease: protanopiya, tritanopiya, deyteranopiya and achromatopsia. Protanopiya is a type of a color blindness at which perception of red shades is broken. At a tritanopiya patients do not distinguish a blue-violet part of a range. In turn, the deyteranopiya is characterized by inability to differentiate green color. In case of total absence of ability to color perception it is about achromatopsia. Patients with this pathology see everything in black-and-white shades.
But defect of perception of one of primary colors is most often observed that testifies to an abnormal trikhromatiya. Trikhromata with protanomalny sight for differentiation of yellow color deyteranomala – green need a bigger saturation of red shades in the image. In turn, bichromates perceive the lost part of color scale with impurity of the kept spectral shades (a protanopa – with green and blue, deyteranopa – with red and blue, tritanopa – with green and red). Also distinguish a red-green blindness. In development of this form of a disease the key part is assigned to the mutation which is genetically linked to a floor. Pathological sites of a genome are localized in the H-chromosome therefore men are ill more often.
Diagnosis of daltonism
The color test of Ishikhar, FALANT test, a research by means of an anomaloskop and polychromatic tables Rabkin is applied to diagnosis of daltonism in ophthalmology.
The color test of Ishikhar includes a series of photos. On each of drawings spots of various flowers which in total create a certain drawing which part at patients drops out from a field of vision therefore they cannot call that is drawn are represented. Also the test includes the image of figures – the Arab figures, simple geometrical symbols. The background of a figure of this test differs a little from the main background therefore patients with daltonism often see only a background since it is heavy to them to differentiate minor changes in color scale. The children who are not distinguishing figure can be examined by means of special children's drawings (a square, a circle, the car). The principle of diagnosis of daltonism according to Rabkin's tables is similar.
Carrying out an anomaloskopiya and FALANT test is justified only in special cases (for example, at acceptance for work with special requirements to color sight). By means of an anomaloskopiya it is possible not only to diagnose all types of violation of color perception, but also to study influence of level of brightness, duration of observation, color adaptation, pressure and composition of air, noise, age, a training on distinction of color and impact of medicines on operation of the receptor device. The technique is used for setting standards of perception and distinction of color for the purpose of professional suitability assessment in certain spheres, and also control of the carried-out treatment. FALANT test is applied in the USA to inspection of candidates for military service. For test passing at a certain distance it is necessary to define the color radiated by a beacon. The luminescence of a beacon is formed by means of merge of three flowers which are a little muffled by the special filter. The persons having daltonism cannot call color, but was proved that 30% of patients with an easy form of a disease successfully pass test.
Congenital daltonism can be diagnosed at late stages of development since patients often call colors not such as they see them in connection with the standard concepts (a grass – green, the sky – blue etc.). At the burdened family anamnesis it is necessary to undergo inspection at the ophthalmologist as soon as possible. Though the classical form of a disease is not inclined to a progression, but at the secondary daltonism caused by other diseases of an organ of vision (a cataract, an age makulodistrofiya, diabetic neuropathy) the tendency to development of a miopiya and dystrophic damages of a retina therefore immediate treatment of the main pathology is required is noted. The color blindness does not influence other characteristics of sight therefore decrease in sharpness or narrowing of a field of vision at genetically determined form is not connected with this disease.
Additional researches are shown in case of the acquired disease forms. The main pathology as which symptom daltonism acts can lead to violation of other parameters of sight, and also provoke development of organic changes of an eyeball. Therefore with the acquired form it is recommended to patients to carry out a tonometriya, an oftalmoskopiya, perimetry, refractometry and biomicroscopy annually.
Treatment of daltonism
Specific methods of treatment of congenital daltonism are not developed. Also the color blindness which arose against the background of genetic pathologies does not give in to therapy ( Lebera, dystrophy of flasks). Symptomatic therapy is based on use of tinted filters for points and contact lenses which help to lower extent of clinical displays of a disease. In the market there are 5 types of contact lenses of various colors for correction of daltonism. Criterion of their efficiency are 100% test passing of Ishikhar. Earlier the special software and cybernetic devices (ah-borg, cybernetic eyes, GNOME) helping to improve orientation in a color palette during the work was developed.
In some cases it is possible to eliminate symptomatology of the acquired violation of color sight after treatment of the main disease (neurosurgical treatment of injuries of a brain, surgery on elimination of a cataract etc.).
Forecast and prevention of daltonism
The forecast at daltonism for life and working capacity favorable, but this pathology worsens quality of life of the patient. The diagnosis of a color blindness limits choice of profession in those areas where the color perception plays an important role (the military personnel, drivers of commercial transport, physicians). In some countries (Turkey, Romania) issue of the driving license is forbidden by sick daltonism.
Specific preventive measures for the prevention of this pathology it is not developed. Nonspecific prevention consists in consultation by the geneticist of families with closely related marriages when planning pregnancy. To patients with diabetes and the progressing cataract it is necessary to have two times a year examination at the ophthalmologist. During training of the child with defect of color perception in elementary grades it is necessary to use special materials (tables, cards) with contrast colors.