Deuteranopia is a defect in color vision

Today, deuteranopia is recognized as the most common form of abnormal color perception.

What is it? This is a deficiency of color vision, when the retina of the eye does not react to the green color of the spectrum. In ICD-10, this visual disorder, like other anomalies of color perception, has the code - H53.5

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Epidemiology

Some difficulty with color vision is experienced by about 8% of men and less than 1% of women. The most commonly identified types are protanopia and deuteranopia.

Deuteranopia is estimated to occur in approximately 5-6% of the male population, mostly in its mild form, deuteranomia.

In 75% of all cases of "green-red color blindness," the defect is caused by a lack of pigment in the photoreceptors (M-cones) of the retina.

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Causes deuteranopias

Color vision defects such as color blindness and deuteranopia are usually genetic, associated with inherited recessive alleles of the X-chromosome genes that code for pigments in the photoreceptor cells of the retina.

Moreover, the defect is inherited only by men – with an X chromosome from mothers who have normal color perception (due to the presence of two X chromosomes), but they are carriers of the abnormal gene.

This is the reason for the absence of pigment in the photoreceptors of the retina - cones that perceive green color.

Deuteranopia and protanopia (inability to perceive colors in the red part of the spectrum) can be the result of genetic or sporadic degeneration of cones, hereditary retinal dystrophy, congenital Stargardt disease (a rare juvenile form of macular degeneration of the retina).

In addition, cone dystrophy is accompanied by such congenital pathologies as Bardet-Biedl syndrome, Leber's amaurosis, Refsum disease, Butt disease, NARP syndrome (neuropathy, ataxia and retinitis pigmentosa), and the genetic neurodegenerative disorder SCA 7 (spinal ataxia type 7).

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Risk factors

Ophthalmologists do not exclude the possibility of acquired deuteranopia, including the following risk factors: [ 8 ]

• development of functional disorders of color transmission by retinal receptors due to damage to the retina due to eye injuries; cerebral hemorrhages and tumors (in particular, in the V4 area of the visual cortex);
• loss of retinal photoreceptors associated with age-related macular degeneration, as well as other ophthalmological diseases (cataracts, glaucoma, diabetic retinopathy);
• disruption of nerve impulse conduction due to damage to the optic nerve in retrobulbar neuritis or multiple sclerosis.

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Pathogenesis

The retina of the eye 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 types of photopigment (light-sensitive molecule).

The function of color discrimination is performed by three types of cones (S, M and L); each cone contains a light-sensitive pigment, photoopsin, of the G-protein receptor (guanine nucleotide-binding protein) family, embedded in the plasma membrane.

Each type of photoreceptor cone cell has its own type of photoopsin, which differs by several amino acids and corresponds to its absorption spectrum (range of light waves): red (L-cones) absorb longer waves (500-700 nm), green cones (M) - medium (450-630 nm), and S-cones, which perceive blue color, react to the shortest waves (400-450 nm).

At the same time, a third of the photoreceptors are 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, chlorolab or MWS opsin. This photopigment is an integral membrane protein, 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.

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Symptoms deuteranopias

The only symptom of deuteranopia is a distortion of the color spectrum compared to normal.

People with this type of color anomaly see red apples or roses as dirty yellow or brownish-green and do not distinguish between shades of red and green. The eyes perceive pink, orange, red and burgundy as a range of green and yellow-green shades of varying intensity; purple turns into gray, and purple eggplants literally look blue.

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Diagnostics deuteranopias

All this is revealed by the deuteranopia test – the same as the test for color blindness, which is carried out using Rabkin tables. All the details are in the materials –

• Color vision
• Testing color perception and color vision

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Treatment deuteranopias

As with color blindness, there is currently no cure for deuteranopia, despite ongoing medical research into genetic engineering.

However, glasses for color blind people with ColorCorrection System lenses were accidentally invented, which improve, or more precisely correct, color perception, but only during daylight hours (they do not function under artificial lighting).

Deuteranopia and Driver's Licenses

Considering the color of traffic lights and vehicle side lights, as well as the increased risk of accidents in the event of a driver's lack of normal perception of green and red, it is prohibited to issue driving licenses to people with deuteranopia.

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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 a conscript is exempted from military service. But when entering service under a contract or submitting documents for admission to a military educational institution, the medical commission may reject the applicant's application.