Deuteranopia - lack of color vision
Last reviewed: 23.04.2024
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Today, deuteranopia is recognized as the most common form of abnormal color perception.
What it is? This is such a lack of color vision, when the retina does not respond to the green color of the spectrum. In ICD-10, this visual impairment, like other color perception abnormalities, has the code - H53.5
Epidemiology
About 8% of men and less than 1% of women experience certain difficulties with color vision. The most frequently identified species are protanopia and deuteranopia.
It is estimated that deuteranopia occurs in approximately 5–6% of the male population, mainly in its moderate form, deuteranomy.
In 75% of all cases of "green-red color blindness" the defect is caused by the lack of pigment in the photoreceptors (M-cones) of the retina.
Causes of the deuteranopia
Defects in color vision, such as daltonism and deuteranopia, are usually genetic, associated with the inherited recessive alleles of X-chromosome genes encoding retinal photoreceptor cell pigments.
Moreover, the defect is inherited only by men - with the X chromosome from mothers who have normal color perception (due to the presence of two X chromosomes), but they are carriers of an abnormal gene.
This is the reason for the lack of pigment in the photoreceptors of the retina - cones that perceive the green color.
Deuteranopia and protanopia (the inability to perceive colors in the red part of the spectrum) can be the result of genetically determined or sporadic degeneration of cones, hereditary retinal degeneration, and congenital Stargardt disease (a rare juvenile form of retinal macular degeneration).
In addition, congenital pathologies such as Bardet-Bidle syndrome, Leber amaurosis, Refsum disease, Butta disease, NARP syndrome (neuropathy, ataxia and retinitis pigmentosa), genetic neurodegenerative disorder SCA 7 (spinal ataxia type 7) are accompanied by cone dystrophy.
Risk factors
Ophthalmologists do not exclude the possibility of acquired deuteranopia, including in risk factors:
- development of functional impairment of retinal receptor color transmission due to its damage due to eye injuries; cerebral hemorrhages and tumors (particularly in the V4 region of the visual cortex);
- loss of photoreceptors of the retina associated with age-related macular degeneration, as well as other ophthalmologic diseases (cataract, glaucoma, diabetic retinopathy);
- violation of the conduction of nerve impulses due to damage to the optic nerve with retrobulbar neuritis or multiple sclerosis.
Pathogenesis
The retina absorbs photons of light and converts them into visual signals transmitted to the brain. And this process is carried out by two main types of photoreceptor cells - rods and cones, which have different shapes, functions and type of photopigment (photosensitive molecule).
The function of distinguishing colors is performed by three types of cones (S, M and L); Each cone contains photosensitive photoopsin, a family of G-protein receptors (guanine nucleotide-binding proteins) embedded in the plasma membrane.
Each type of photoreceptor cone cells has its own type of photoopsin, characterized by several amino acids and corresponding to its absorption spectrum (wavelength range): red (L-cones) absorb longer wavelengths (500-700 nm), green cones (M) - medium ( 450-630 nm), and S-cones that perceive blue color react to the shortest wavelengths (400-450 nm).
At the same time, a third of the photoreceptors is tuned to medium waves. And the pathogenesis of deuteranopia is associated with the absence or functionally noticeable deficiency of the corresponding photopigment, which is called photopsin II, M-opsin, OPN1MW, chloro-lab or MWS opsin. This photopigment, an integral membrane protein, is encoded by the OPN1MW gene on the X chromosome.
Without it, M-cones do not perceive the waves of their (green) spectrum and, accordingly, cannot transmit the correct signal to the visual cortex of the brain.
[13], [14], [15], [16], [17], [18], [19], [20], [21], [22], [23]
Symptoms of the deuteranopia
The only symptom of deuteranopia is a distortion of the color spectrum in comparison with the usual one.
Red apples that have this type of color anomaly are seen as dirty yellow or brownish green and do not distinguish between shades of red and green. In the form of green gamma and yellow-green shades of varying intensity of the eye perceive pink, orange, red and burgundy; purple turns gray, and purple eggplants literally look blue.
Diagnostics of the deuteranopia
All this finds out the test for deuteranopia - the same as for the detection of color blindness, which is carried out using Rabkin tables. All the details in the materials -
Who to contact?
Treatment of the deuteranopia
As in the case of color blindness, the treatment of deuteranopia is not yet possible - despite the ongoing medical research in the field of genetic engineering.
However, glasses for color blindness with the ColorCorrection System lenses were invented by chance, which improve, more precisely correct color perception, but only during daylight hours (they do not function under artificial light).
Deuteranopia and driver's license
Given the color of traffic lights and parking lights of vehicles, as well as an increased risk of accidents in the absence of a normal perception of green and red by the driver, it is prohibited to issue a driver's license in case of deuteranopia.
Deuteranopia and the army
This type of color anomaly, like color blindness, is not listed in the list of diseases, in the presence of which the draftee is exempted from military service. But when he enters a contractual service or submits documents for admission to a military educational institution, the medical board may reject the applicant’s application.
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