Also called color blindness in its hereditary form, dyschromatopsia is a vision disorder that affects the perception of colors. The most frequent is that which concerns the perception of green and red which are sometimes confused. Its detection goes through tests allowing to specify the colors which are not perceived.

Normal eye vision perceives only part of the electromagnetic spectrum of colors passing between 400 nanometers (purple) and 800 nanometers (red). Between these two values, the perceived colors range from blue to orange via green and yellow. 

Many people partially perceive these colors and suffer from what is called “dyschromatopsia”. The best known of these dyschromatopsias is color blindness which is the hereditary form of this vision disorder. It affects, to varying degrees of severity, 8% of the male population. It can be a real handicap in professional (airline pilot, police, electronics and electricians, etc.) and private life.

But there are other forms of dyschromatopsia which are acquired mostly related to degeneration of the central part of the retina, called “macula”. The retina is a membrane that lines the back of the eye and perceives light rays to transmit them to the brain, allowing eye vision. In the macula, there are a large number of receptors responsible for color perception (cones). It is these receptors whose function is impaired by the disease.

The most common of these diseases is “age-related degeneration” (AMD) which is a disease affecting the elderly and which changes the anatomy of the macula, in particular its cones which perceive colors.

They can therefore be of genetic origin for color blindness affecting the X chromosome. This hereditary dyschromatopsia is transmitted by women and it is men who suffer from this vision disorder. 

The symptoms of this disease, when it is hereditary, are symmetrical and affect both eyes and this anomaly persists in a stable manner over time. The other visual functions (reliefs, shapes, luminosity) are respected and dyschromia most often concerns red and green.

Other causes are possible, but they are acquired as for AMD due to old age, dyschromatopsia linked to intoxication (tobacco, etc.), to a disease (cataracts, diabetes, retinal detachment, glaucoma, high myopia, impairment optic nerve …) or ocular trauma (accident).

These dyschromatopsias are then asymmetrical, affecting only one eye or both, but not at the same time, evolving over time if the cause is not treated, concern several color alterations and are associated with other visual disturbances (blur, distortion of images, loss of visual acuity, etc.).

The diagnosis of dyschromatopsia, whether inherited or acquired, begins with color tests. The two most widely used tests are the Ishihara test and the Fameworth test. 

The Ishihara test

It consists of 21 plates which seem to present the same colors (pseudo-isochromatic) but which in reality are composed of colored dots grouped with two colors of varying intensity, differentiated by healthy people, but confused into a single color for the subjects. suffering from dyschromatopsia.

The Fameworth test 

It comes in the form of several colored discs that the patient must order according to their color and tone. It measures the severity of dyschromatopsia.

Other tests are offered to children from the age of three, simpler and more fun, such as the children’s version of the Ishihara test with eight boards made up of circles, squares and lines or the Verriest test made up of colored tokens. to organize like dominoes.

Apart from hereditary dyschromatopsia (color blindness), various additional examinations will look for other causes such as a blood test for diabetes, an ophthalmological examination to explore the retina through a fundus, the demonstration of ” a cataract or the search for intoxication (tobacco, antimalarials, corticosteroids, etc.).

Hereditary dyschromatopsia is not treatable, but glasses and contact lenses that filter out missing colors may be prescribed.

Treatment of other dyschromatopsias is that of the cause once the diagnosis is made. Discontinuation of drugs causing eye pathologies and dyschromatopsia, treatment of AMD, glaucoma, diabetes, retinal detachment in severe myopia …