Color blindness facts > Types of color blindness

A person with perfect color perception is called normal trichromat. In the cases of disordered color sense we first of all distinguish whether it is congenital or acquired. The cases of congenital disorders are more numerous and more significant.

Congenital disorders

Congenital disorders can be labeled also as hereditary and because they were inherited there is no treatment whatsoever; however nowadays they can be corrected to some extent by visual aids. There are more types of congenital disorders and we can divide them according to the degree of disorder of the color vision to anomalous trichromatism, dichromatism and monochromatism. Moreover, we divide congenital disorders according to which color is perceived incorrectly or is not perceived at all. Congenital disorders of color sense are mostly connected with red and green color. Together they represent 99% of the overall number of patients.

Anomalous trichromatism

Patients suffering from anomalous trichromatism have a decreased ability to perceive one of the basic colors. There are three types of cones located on the retina but one type does not work perfectly and that is why a color perception is formed in other ratio than in the case of normal trichromat. In the case of anomalous trichromatism we add the suffix -anomaly and we divide anomalous trichromats according to which color is perceived incorrectly. Protanomaly is a disorder of the perception of red color. Deuteranomaly is a disorder of the perception of green color and tritanomaly is a disorder of the perception of blue color. A disorder of the perception of blue color is very rare and it almost does not occur. In the cases of green and red colors the occurrence is substantially higher.

Dichromatism

Dichromatism is the most common type of congenital disorder of color sense. Dichromats have only two functional types of cones and therefore one of the three basic colors is not being distinguished. From the information provided by two properly functional types of cones dichromats create or try to create all the colors.  However, some colors are perceived only as brown shades even though they are capable of distinguishing other colors properly and without any problems. The orientation of dichromats as far as colors are concerned is not according to the tones but according to the brightness of individual color shades. For labeling dichromatism we use the suffix – anope. We divide dichromats in the same way as we divide anomalous trichromats - according to one of the basic colors which is perceived incorrectly. This means that a person who does not see red color is called protanope, deuteranope is a person who does not see green color and tritanope does not see blue color.

Monochromatism

Monochromatism is a functional disorder when a person does not distinguish any color – he does not have the ability of color vision. It is only in this case when we can talk about total color blindness. In most of the cases it is a disorder of cones which may not be found on the retina. A patient with monochromatism distinguishes color objects which are being observed only according to their brightness. However, this type of disorder of color sense is very rare. In most of the cases monochromatism is connected with many other sight disorders. Central visual sharpness is usually diminished and it cannot be improved even with the help of eyeglasses or contact lenses. Nystagmus and high astigmatism can also occur. Only very rarely we can meet with total color blindness without any other functional disorders.