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Visual Defects

People with normal color vision have three types of vertebral cells in their retinas, so they can quickly and correctly perceive and discriminate between red, green, and blue primary colors, and can use red, green, and blue primary colors to mix and match colors. However, some people are abnormally color-sensitive due to visual defects, such as congenital vertebral cell hypoplasia or acquired damage to the visual nerve, resulting in the inability to distinguish certain colors. In terms of the severity of the abnormality, they can be divided into those with mild abnormal color vision and those with severe abnormal vision, which also corresponds to color weakness and color blindness.

1. Color Weakness

Color vision is also known as mild abnormal color vision. Patients with color weakness can distinguish red, green and blue primary colors, but their discrimination ability is poor, such as for red and green, there must be a long interval on the corresponding spectrum to distinguish; color weakness patients can mix colors according to red, green and blue, only the relative proportions of red, green and blue are different from those of normal color vision.
Color weakness is divided into three categories, which are red weakness, green weakness, and blue weakness. Among them, red weakness is poorer for red discrimination; green weakness is poorer for green discrimination; blue weakness is poorer for blue and yellow discrimination.

There is no clear and strict boundary between color weakness and normal color vision, and it mostly occurs later in life, such as caused by vision-related diseases.

2. Color Blindness

Color blindness is a serious abnormal color vision, color blindness can be divided into total color blindness and local color blindness, which, total color blindness patients retina without vertebral cells, only rod cells, so can only feel the grayscale changes of black and white; local color blindness is also known as dichromatopsia, local color blindness can be divided into red-green blindness, blue-yellow blindness. -yellow blindness. Red-green blindness can not distinguish between red and green, and is divided into red blindness and green blindness, respectively, called type A color blindness, type B color blindness, blue-yellow blindness is called type C color blindness, can not distinguish between blue and yellow, only to red, green color vision. Normal color vision and the three color blind see red, green, blue and white as shown in the figure below.

visual defects

John Dalton was the first scientific monograph to address color blindness in his 《Bizarre Facts About Color Vision》. Dalton himself was a type A colorblind person, so it is common to refer to red-green colorblindness as Dalton colorblindness.


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