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Color anomaly: types, verification with pictures
Last reviewed: 12.07.2025
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The ability of the eyes to distinguish objects based on the wavelengths of light they reflect, emit, or transmit provides a person with color vision. A color vision disorder, or color anomaly, occurs when the cells of the photosensory layer of the retina do not function correctly, which is why a person may not be able to distinguish between red and green colors or may not perceive blue at all.
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Epidemiology
Problems with color perception affect up to 8% of men and only 0.5% of women. According to other data, color anomaly affects one in twelve men and one in two hundred women. At the same time, the prevalence of complete lack of color vision (achromatopsia) is one case per 35 thousand people, and partial monochrome is detected in one person out of 100 thousand.
Statistics estimate the frequency of detection of various types of color anomalies depending on gender as follows:
- in men: protanopia – 1%; deuteranopia – 1-1.27%; protanomaly – 1.08%; deuteranomaly – 4.6%.
- in women: protanopia – 0.02%; deuteranopia – 0.01%; protanomaly – 0.03%; deuteranomaly – 0.25-0.35%.
It is believed that two-thirds of cases of color vision deficiency are due to anomalous trichromacy.
Causes color anomalies
In ophthalmology, the causes of color anomalies related to color vision deficiencies (code H53.5 according to ICD-10) are classified as primary (congenital) and secondary (acquired as a result of certain diseases).
Color anomalies are most often present at birth, as they are inherited as an X-linked recessive change at the level of retinal photopigments. The most common is color blindness (red-green color blindness). This color anomaly is mainly observed in males, but is transmitted by females, and at least 8% of the female population are carriers. Also read - Color blindness in women
Ophthalmic causes of color perception disorders may be associated with
- retinal pigment epithelium dystrophy;
- retinitis pigmentosa (hereditary degeneration of the retinal photoreceptors, which can occur at any age);
- congenital dystrophy of cone photoreceptors;
- detachment of the pigment epithelium in central serous chorioretinopathy;
- vascular disorders of the retina;
- age-related macular degeneration;
- traumatic damage to the retina.
Possible neurogenic causes of color anomalies include disturbances in the transmission of signals from the retinal photoreceptors to the primary visual nuclei of the cerebral cortex, and this often occurs in idiopathic intracranial hypertension with compression of the optic nerve or demyelinating inflammation of the optic nerve (neuritis). Loss of color vision can also occur due to damage to the optic nerve in Devic's disease (autoimmune neuromyelitis), neurosyphilis, Lyme disease, and neurosarcoidosis.
Less common causes of secondary color anomaly include cryptococcal meningitis, abscess in the occipital region of the brain, acute disseminated encephalomyelitis, subacute sclerotic panencephalitis, arachnoid adhesions, and cavernous sinus thrombosis.
Central or cortical achromatopsia may result from abnormalities in the visual cortex in the occipital lobe of the brain.
While genetic defects of color vision are always bilateral, acquired color anomaly can be monocular.
Risk factors
In addition to heredity and the diseases listed, risk factors include trauma or bleeding in the brain, cataracts (clouding of the lens) and age-related deterioration of the retina's ability to differentiate colors, as well as chronic cobalamin (vitamin B12) deficiency, methanol poisoning, the effects of drugs on the brain, and side effects of certain medications.
Pathogenesis
When considering the pathogenesis of color anomaly, it is necessary to describe in general terms the functional features of the pigment epithelium of the retina (their inner shell), most of which consists of photoreceptor (neurosensory) cells. According to the shape of their peripheral processes, they are called rods and cones. The former are more numerous (about 120 million), but do not perceive color, and the sensitivity of the eyes to color is provided by 6-7 million cone cells.
Their membranes contain retinylidene light-sensitive proteins of the GPCR superfamily – opsins (photopsins), which function as color pigments. L-cone receptors contain red LWS-opsin (OPN1LW), M-cone receptors contain green MWS-opsin (OPN1MW), and S-cone receptors contain blue SWS-opsin (OPN1SW).
Sensory transduction of color perception, that is, the process of converting photons of light into electrochemical signals, occurs in S-, M-, and L-cone cells through receptors associated with opsins. Scientists have discovered that the genes of this protein (OPN1MW and OPN1MW2) are responsible for the pigments of color vision.
Red-green color blindness (daltonism) is caused by the absence or alteration of the coding sequence for LWS opsin, and this is the responsibility of genes on the 23rd X chromosome. And congenital insensitivity of the eyes to blue color is associated with mutations in the SWS opsin genes on the 7th chromosome, and this is also inherited in an autosomal dominant manner.
In addition, some cone receptors may be completely absent in the retinal pigment epithelium. For example, in tritanopia (dichromatic color anomaly), S-cone receptors are completely absent, and tritanomaly is a mild form of tritanopia, in which case S-receptors are present in the retina, but have genetic mutations.
The pathogenesis of acquired color vision deficiency of neurogenic etiology is associated with a disruption in the conduction of impulses from photoreceptors to the brain due to the destruction of the myelin sheath covering the optic nerve (II cranial nerve).
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Symptoms color anomalies
The key symptoms of various types of color blindness manifest themselves in the form of complete color blindness or distortion in perception.
Achromatopsia is characterized by a complete lack of color vision. Complete shutdown of the red photoreceptors of the retina means protanopia, and a person sees red as black.
Deuteranopia is characterized by distortions of red and green colors; in particular, instead of light shades of green, a person sees dark shades of red, and instead of violet, which is close in spectrum, a person sees light blue.
People with tritanopia confuse blue with green, yellow and orange appear pink, and purple objects appear dark red.
In anomalous trichromatism, all three types of cone photoreceptors are present in the retina, but one of them is defective – with a shifted maximum sensitivity. This leads to a narrowing of the perceived color spectrum. Thus, in the case of protanomaly, there is a distortion in the perception of blue and yellow colors, in deuteranomaly there is a discrepancy in the perception of shades of red and green – a mild degree of deuteranopia. And the symptom of tritanomaly is manifested in the inability to distinguish colors such as blue and violet.
Forms
Normal color vision, according to the trichromatic theory, is provided by the sensitivity of three types of photoreceptor cells of the retina (cones), and according to the number of primary colors that are necessary to correspond to all spectral shades, people with genetically determined color anomalies are divided into monochromats, dichromats or anomalous trichromats.
The sensitivity of photoreceptor cells varies:
S-cone receptors react only to short waves of light - with a maximum length of 420-440 nm (blue color), their number is 4% of photoreceptor cells;
M-cone receptors, which account for 32%, perceive medium-length waves (530-545 nm), color - green;
L-cone receptors are responsible for sensitivity to long-wavelength light (564-580 nm) and provide the perception of red color.
There are the following main types of color anomalies:
- with monochromaticity - achromatopsia (achromatopsia);
- with dichromacy – protanopia, deuteranopia and tritanopia;
- with anomalous trichromacy – protanomaly, deuteranomaly and tritanomaly.
While most people have three types of color receptors (trichromatic vision), almost half of women have tetrachromacy, that is, four types of cone pigment receptors. This increased color discrimination is associated with two copies of the retinal cone receptor genes on the X chromosomes.
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Diagnostics color anomalies
To diagnose color anomaly in domestic ophthalmology, it is customary to use a color perception test using pseudoisochromatic tables by E. Rabkin. Abroad, there is a similar test for color anomaly by the Japanese ophthalmologist S. Ishihara. Both tests contain many combinations of background images that allow one to determine the nature of the color vision defect.
Anomaloscopy – examination using an anomaloscope – is considered the most sensitive diagnostic method for detecting color perception disorders.
Differential diagnosis
Differential diagnosis is necessary to identify the causes of acquired (secondary) color perception disorder, which may require CT or MRI of the brain.
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Treatment color anomalies
Congenital color vision anomalies are incurable and do not change over time. However, if the cause is an eye disease or injury, treatment may improve color vision.
Using special tinted glasses or wearing red tinted contact lenses in one eye may improve some people's ability to distinguish colors, although nothing can make them actually see the missing color.
Color vision deficiency can have certain occupational limitations: nowhere in the world are colorblind people allowed to work as pilots or railroad drivers.
Color anomaly and driving license
If, when passing the test (using Rabkin tables), a color anomaly of degree A is detected, then driving a car is not prohibited.
When the test reveals more significant deviations in color perception and a color anomaly of degree C with a complete inability to distinguish green from red is determined, the prognosis regarding obtaining a driver's license is not encouraging: colorblind people are not issued one.
However, in the USA, Canada, Great Britain, Australia and some other countries, red-green color blindness is not an obstacle to driving. For example, in Canada, traffic lights are usually differentiated by shape to make it easier for drivers with this color anomaly to recognize the signals. However, there are still red car indicators that light up when braking…