Dichromasia

If a person distinguishes only two primary colors, then this state is called dichromasia. Consider the causes of this pathology, types, methods of diagnosis, treatment.

Color perception disorders are serious anomalies, which are both congenital and acquired. Hereditary mutations and other pathological processes in the organs of the optical system lead to functional disturbances in the work of the cone system. The disease is transmitted only by the recessive type. It is diagnosed in 8% of men and 0.4% of women. Moreover, it is women who are asymptomatic carriers of the mutant gene.

The main qualities of color:

• Tone is a sign of color and depends on the length of the light wave.
• Saturation - is determined by the proportion of the main tone with impurities of a different color.
• Brightness (lightness) - the degree of dilution is white.

At normal perception, the person distinguishes set of shades of all basic colors. This condition is called normal ophthalmology trichromasia. If there are certain violations with the recognition of color spectrum waves, then the patient can be diagnosed with such conditions: a protan-defect (red pathology), a tritane-defect (blue) and a deuter-defect (green color). Problems with the recognition of any primary color, as a rule, is green, less often red is distinguished by the degree of disturbances: anomalous trichromasia, dichromasia, monochromasia.

If a person perceives two primary colors, then this is dichromasia. For the first time this state was described by a scientist and physician - Dalton, in whose honor the most common anomaly - color blindness is named. With complete color blindness, the world is perceived in black and white shades, and pathology is called monochromasia. Severe disorders of all pigment layers are extremely rare. Dichromasia is more often detected, its diagnosis is carried out with the help of special ophthalmological testing.

[1], [2], [3]

Epidemiology

Medical statistics indicate that dichromasia is more common in men than in women. The disease is associated with damage to the central part of the retina, where there are nerve cells containing three types of color-sensitive pigments of protein origin. Each pigment perceives a certain color: red, blue, green. Their mixing provides normal recognition of paints.

According to statistics, most often diagnose problems with red pigment. At the same time, 8% of men and about 0.4% of women have a red-green color vision defect. In 75% of patients, the recognition of only one color is significantly reduced. Complete color blindness is extremely rare and, as a rule, occurs with other anomalies of the organs of the optical system.

[4], [5], [6], [7], [8]

Causes of the dichromate

The main causes of dichromasia, that is, inability to adequately color recognition, are the violation of the color-sensitive receptors. They are located in the central part of the retina of the eye and are special nerve cells - cones. There are three types of cones that have such characteristics of perception of the main color:

• 1 pigment - captures a green spectrum with a length of 530 nm.
• 2 pigment - recognizes red with a wavelength of 552-557 nm.
• 3 pigment is a blue spectrum with a length of 426 nm.

If all three pigments are present in the cones, then this state is the norm and is called trichromation. The causes of visual anomalies are congenital and acquired:

1. An hereditary factor is a mutation of the female X chromosome. That is, the disease is transmitted from the mother carrier to the son. It is in men that this pathology manifests itself more often, since they do not have an additional X-chromosome in the gene set that could eliminate the mutation. According to statistics, the disorder occurs to 5-8% of men and 0.4% of women.
2. The acquired form is not related to the transfer of the mutant gene. Occurs when the dystrophic or inflammatory lesions of the retina. The disorder can develop with atrophy of the optic nerve, brain diseases, various trauma of the skull and eyes, when taking medications or age-related pathologies.

This type of disorder is most often manifested only in one eye. Over time, the pathology becomes more pronounced. On its background, I can develop violations of the transparency of optical media, that is, the pathology of the macular area of the retina. It is also possible to reduce visual acuity and visual field disturbance.

Knowing the causes of the pathological condition, the process of diagnosis and correction of visual anomalies is greatly simplified.

[9], [10]

Risk factors

The inability to adequately discern color has certain risk factors that increase the chance of developing pathology. Consider these:

• Genetic predisposition. If the family history was color blind, then the probability of obtaining a pathology by inheritance increases.
• Male gender - men are more likely to suffer from color blindness for women.
• Some medications can damage the optic nerves and the retina.
• Age-related degenerative changes (clouding of the lens, cataracts).
• Retinal injuries with macular damage.
• Optical neuropathy Leber - a genetic pathology, which manifests itself in the defeat of the optic nerves.
• Parkinson's disease - due to the disorder of conduction of nerve impulses, the correct formation of the visual image is disturbed.
• Defeat of the brain (occipital lobe) caused by trauma, stroke or neoplasm.

During the examination, the ophthalmologist takes into account the above risk factors, which simplifies the formulation of the final diagnosis.

[11], [12], [13], [14], [15]

Pathogenesis

Dichromasia is associated with a violation of the recognition of color spectrum waves. The pathogenesis of a congenital anomaly is based on the absence of one or more color-sensitive receptors in the central part of the retina. With the acquired form, the receptors, that is, the cones, are affected.

Allocate such differences between the mechanism of development of congenital and acquired disease:

• Congenital pathology is characterized by reduced sensitivity only to red or green. Acquired - to red, green and blue.
• With the acquired disorder, contrast sensitivity is reduced, with hereditary disorders not reduced.
• The genetic form is stable, while the acquired form can vary in form and degree.
• The level of functionality with hereditary form is reduced, but stable, in the second case, changes are possible.

In addition to the above differences, the genetic disorder is binocular and is more common in men, the acquired form can be both monocular and binocular, affecting equally both men and women.

[16], [17], [18], [19], [20], [21], [22]

Symptoms of the dichromate

With normal color perception, all the primary colors are different. Symptoms of dichromasia are manifested by loss of one of the three pigments from the color vision: green, red or blue. That is, the patient perceives only two primary colors.

If the disease is caused by genetic factors, then it manifests itself by such anomalies:

• The defect is a red color.
• Tritane defect is blue.
• Deuter-defect is green.

Patients with dichromasia perceive the lost part of the color spectrum with the help of an admixture of preserved spectral shades:

• Protanopes - green and blue.
• Tritanopes are green and red.
• Deiteranopes are red and blue.

There is also a red-green blindness. The development of this form of the disease is more closely associated with a genetically sex-linked mutation. Most often, her symptoms are manifested in men.

[23], [24], [25], [26]

First signs

Manifestations of dichromasia are individual for each individual case. The first signs largely depend on the cause of the disease. Most often there are slight disorders of color perception:

• Violation of the perception of red and green.
• Problems with recognizing blue and green.
• Low visual acuity.
• Nystagmus.

In especially severe cases, the disease manifests itself in a gray perception of all colors.

[27], [28], [29]

Dichromasia, protanopia

One of the most common problems with the perception of colors (recognition of only two pigments) is dichromasia. Protanopia is its variety. This form of the disease is characterized by the inability to distinguish between red. The disorder is based on the absence of the photosensitive pigment of erythrolab in the retinal cones.

With protanopia, the patient perceives the green (yellow-green) as orange (yellow-red), blue can not be distinguished from purple, but distinguishes between blue and green, and green from dark red.

To date, pathology is incurable, but protanopia does not affect the quality of life. To correct the disorder use special lenses or glasses, glasses blocking the hit on the eyes of bright color. Some patients are helped to wear sunglasses, since dim light promotes the activation of cones.

Stages

There are such degrees of dichromasia:

• A slight decrease in the perception of color.
• Deeper frustration.
• Loss of perception of the pigment (most often green or red).

Non-perception of one of the primary colors significantly changes the perception of others. Proceeding from this, it is very important to diagnose pathology and determine its degree. This is especially true for people whose work requires a full-fledged color vision (medical workers, pilots, drivers, military, chemical industry workers and radio technicians, people working with mechanisms).

[30], [31], [32], [33], [34], [35]

Forms

Dichromasia refers to visual disturbances of moderate severity. It is based on the malfunctioning of one of the three receptors. The disease occurs when a certain pigment is broken, and color recognition occurs only in two planes.

Types of pathological condition:

• Protanopia - does not perceive light with a wavelength of 400 to 650 nm instead of the usual 700 nm. There is a complete loss of red, that is, the dysfunction of its photoreceptors. The patient does not see scarlet flowers, perceiving them as black. Purple does not distinguish from blue, and orange represents a dark yellow. In this case, all shades of green, orange and yellow, the length of which is great for stimulating the receptors of blue, are represented in a yellow tone.
• Deuteranopia - loss of photoreceptors of the second type. The patient does not distinguish between green or red.
• Tritanopia is an extremely rare disorder with complete absence of blue pigment. The disease is associated with the seventh chromosome. Blue looks with a green tint, violet - dark red, orange - pink.

From the type of visual anomaly and degree of severity depends the method of its correction and the overall prognosis for the patient.

[36], [37], [38]

Complications and consequences

As a rule, dichromasia caused by hereditary factors does not cause health problems. Various consequences and complications are possible if the disease has acquired form. That is, when the disorder is associated with other pathologies, for example, traumas of the retina of the eyes or the brain, tumor neoplasms.

The patient is prescribed correction of vision peculiarities and complex treatment of the caused complications. Recovery in this case depends on the severity of pathological consequences.

[39], [40], [41]

Diagnostics of the dichromate

To determine the level of color perception in the patient, a set of various studies is shown. Diagnosis of dichromasia is carried out using the following methods:

• Pigment methods

The doctor uses special polychromatic, that is, multi-color tables. They are filled with multi-colored circles of equal brightness. In the center of each table there are figures or geometric figures of different shades that the patient should name. The ophthalmologist fixes the number of correct answers, noting the color zone. Based on the results of the study, the degree and type of visual pathology is determined. If the patient can not distinguish between obvious signs, but without difficulty calling the hidden signs, then he is diagnosed with a congenital visual anomaly.

• Spectral methods.

Diagnosis is carried out using special instruments. This may be the Rabkina spectroanalamoscope, the apparatus of Girenberg and Ebnei, or the Nagel anomaloscope. Anomaloscope is an instrument that doses color mixtures, achieving a subjective equality of colors. The device is used to detect violations in the red-green range. With its help, it is possible to diagnose not only dichromasia, but its degree and species, that is, deuteranopia or protanopia.

In most cases, the above methods can diagnose a visual anomaly, regardless of the nature of its origin. There are also methods to detect the disorder during intrauterine development. Such a diagnosis is carried out if there are cases of visual anomaly in the family. Pregnant women are prescribed a special DNA test that determines the color blindness gene.

[42], [43], [44], [45], [46],

Dichromatic test

Diagnosing problems with color recognition consists of various tests. The dichromatic test is most often carried out using Rabbin's polychromatic tables or their analogue of Ishihara's tables.

During the test, the patient is shown tables with different images, these can be figures, numbers or chains. The image consists of many small circles with the same brightness. The basic set for testing consists of 27 color tables. If there is a need to clarify the diagnosis, then use all 48 tables.

If during the test a person does not distinguish colors, then for him the table looks homogeneous. People with normal vision distinguish pictures. To conduct testing, you must follow these rules:

• The test should take place in a room with natural light, and the patient should sit with his back to the window.
• It is important to ensure complete peace and relaxation of the subject.
• Show each picture at eye level and at a distance of about 1 m. The viewing time should be within 5-7 seconds.

If the dichromate test is carried out at home on a personal computer and the patient does not distinguish all the colors, then this is not an excuse to get frustrated. As the result of testing largely depends on the color and resolution of the monitor. Diagnosis should only deal with an ophthalmologist.

[47]

Tables for determination of dichromasia

Diagnostic tables for the determination of dichromasia, that is, the level of color perception, allow us to establish the extent of the disorder and its shape. The most commonly used tables are Rubkin, which consist of two groups:

• The basic - 27 tables for differentiation of forms and degrees of frustration.
• Control - 20 tables to clarify the diagnosis during simulation, aggravation or dissimulation.

Diagnostic tables are developed by the principle of the equation of circles of different colors by saturation and brightness. They denote figures and geometric figures that are perceived by color anomalies. At the same time, the symbols allocated in one color are skipped, which the patient does not perceive.

To obtain reliable results, it is very important to comply with all testing rules. The patient should sit with his back to the window or light source. Tables are shown in a strictly vertical plane at eye level of the subject. The time for studying one image should not exceed 5-7 seconds. Diagnostic tables are not recommended to be placed on a table or to be inclined, as this negatively affects the accuracy of the technique and its results.

The answers received as a result of the test are entered in a special card. Normal trichromate reads all the tables, anomalous - more than 12, and a person with dichromasia 7-9. Infringements estimate on a scale of color weakness. In addition to Rubkin's tables, in the clinical practice, Iustova's tables are used to determine the thresholds of color discrimination, that is, the colors of the visual apparatus. Such a comprehensive diagnosis allows you to catch the most minimal differences in the tones of two colors, occupying similar positions in the color range.

Differential diagnosis

Violations of color perception have different forms, types and degrees of severity. Differential diagnosis of dichromasia allows one to separate it from other dysfunctions of photoreceptors.

Differentiation is carried out using polychromatic tables. A patient with color blindness will see all the images as homogeneous, the trichromate will distinguish the images, and the dichromate will determine only some of the suggested pictures.

Based on the results of the studies, a treatment plan is drawn up. Correction is carried out with the help of special lenses. If the disease is caused by a gene mutation during fetal development, then with the help of genetic engineering, missing genes can be introduced into the retina of the eye, which restore normal color recognition.

What is the difference between color and dichromasia?

Functional pathologies of the cone system have several types and forms, which largely depend on the cause of the disorder. Many patients, faced with the problem of color perception, are asking the question, what is the difference between dichromasia and color delicacy?

• Dichromasia is a violation of color vision caused by congenital or acquired factors. Characterized by the lack of a function of one of the three color-sensitive devices. The lost color is compensated by mixing the shades of others.

• Color sweetness is the inability to distinguish between separate shades of colors, but not the colors themselves. That is, the palette is slightly broken, but is present. In most cases this does not cause problems and is found only in complex ophthalmological testing.

Normal color perception is trichromasia. Congenital defects of the organs of the optical system are divided into: a defect perception of red, green or blue. Dichromasia is characterized by complete blindness to one color, and with monochromasia, the patient has a black-and-white perception.

Treatment of the dichromate

Dysfunction of photoreceptors can be associated with both congenital and acquired factors. Treatment of dichromasia of hereditary form, that is, caused by mutation of genes during intrauterine development, is practically not carried out. Only in especially severe cases, as a rule, with complete color blindness, with the help of genetic engineering, the missing genes are introduced into the affected retina.

In the case of treatment of dichromasia of the acquired form, positive results are possible. Let's consider the basic variants of therapy:

1. Surgical treatment - is used in the development of ophthalmic damage, which is associated with the clouding of the lens of the eye. The operation is performed with glaucoma, cataract, retinopathy and other diseases. But if the disorders are associated with the aging process and the natural opacification of the lens of the eye, then such changes are irreversible.
2. Compensation of problems with color perception:
   • Glasses with a bright color lock function are assigned to people whose color vision problems are caused by a bright color that prevents recognition of other colors.
   • Corrective lenses of special purpose - according to the principle of action are similar to the glasses, but can not significantly distort objects.
   • Glasses with colored or dark glasses are recommended for full color blindness. Their therapeutic effect is explained by the fact that in the muffled light the cones of the eye work better.
3. Cancellation or interruption of medication that provoked the inability to adequately discern color. Violation is possible with severe vitamin A deficiency or after taking Chlorquin. In the latter case, the visible objects are painted green. If high bilirubinemia is diagnosed, then the items are colored yellow.

Timely diagnosis and treatment of the pathological condition in the early stages, allows to minimize the risk of dysfunction of photoreceptors.

Prevention

Specific measures to prevent dichromasia does not exist. Prevention is in consultation with a geneticist when planning a pregnancy. This allows us to identify hereditary factors that increase the risk of anomalies.

It is necessary to observe safety precautions and wear protective goggles when working with dangerous substances. Since eye injuries are related to the risk factors of the disease.

People with diabetes or cataracts in the progression stage must undergo a comprehensive diagnosis twice a year from an ophthalmologist. When teaching children of childhood with color defects, it is recommended to use educational materials with contrasting colors.

[48], [49], [50]

Forecast

In general, for life and work capacity, dichromasia has a positive outlook. But the features of vision can worsen the patient's quality of life.

The disorder places a ban on choosing a profession in those areas where the difference in colors is important. If the disease is caused by trauma or other diseases, the prognosis depends entirely on the possibility and effectiveness of their treatment.

Dichromasia and driver's license

People with vision problems have limitations in certain areas of life. To obtain a driver's license other than the ability to drive a car and knowledge of traffic rules, you must provide a medical certificate. The medical commission determines whether a person is fit for transport management.

There is a list of diseases in which driver's license is not issued. First of all, this is the quality of vision. If the visual acuity is diagnosed, then its correction is required for driving. Particular attention is paid to the color perception of the eye. This characteristic is very important, because when it violates the driver will not be able to recognize the colors of the traffic light. With detached retina or glaucoma, driving is prohibited.

Dichromasia and other forms of violation of color perception are grounds for refusal to issue rights to drive a vehicle. That is, dichromation and driver's license are incompatible. But with the possibility of correcting the dysfunction of photoreceptors, there is a chance to get the right.

[51], [52],