What causes color blindness?

Color blindness is quite common in our daily life. It is a color vision disorder caused by congenital reasons. Some colors in the natural spectrum cannot be correctly distinguished. The main cause of color blindness is genetic. For example, red-green color blindness is caused by abnormal genes on the x chromosome, which causes the inability to correctly distinguish red and green. There is no way to completely cure color blindness.

What causes color blindness?

It is generally believed that red and green color blindness is determined by two pairs of genes on the X chromosome, namely the red and green color blindness genes. Because these two pairs of genes are tightly linked on the X chromosome, they are often represented by one gene symbol. Red and green color blindness is inherited in an X-linked recessive manner. Males only have one X chromosome, so they only need one gene to be color blind.

Females have two X chromosomes, so they need a pair of disease-causing alleles to show abnormalities. If a normal woman marries a color-blind man, the father's color-blind gene can be passed on to their daughter via the X chromosome, but not to their son. The daughter then passes the color blindness gene from her father to her son, a phenomenon called cross-inheritance.

Clinical manifestations of color blindness

1. Achromatopsia

It is a complete cone cell dysfunction, which is the opposite of night blindness (rod cell dysfunction). Patients prefer darkness and are afraid of light, which manifests as day blindness. There is only a difference in light and dark, but no difference in color, and the red appears dark and the blue appears bright. In addition, there are symptoms such as poor vision, amblyopia, central scotoma, and pendulum nystagmus. It is the most severe form of color vision deficiency and is less common.

2. Red-color blindness

Also known as the first color blindness. The patient is mainly unable to distinguish the color red, and cannot distinguish red from dark green, blue from purple-red, and purple. Green is often seen as yellow, purple is seen as blue, and green and blue are mixed as white.

3. Deuteranopia

Also known as second color blindness, patients cannot distinguish between light green and dark red, purple and cyan, purple and gray, and perceive green as gray or dark black. In clinical practice, red-green color blindness and green-color blindness are collectively referred to as red-green color blindness, which is more common. The color blindness we usually talk about usually refers to red and green color blindness.

4. Blue-yellow color blindness

This type of color blindness is also called third color blindness. Patients usually confuse blue and yellow colors. This symptom is relatively rare.

5. Panchromatosis

Also known as red, green, blue and yellow weak. The color vision impairment is lower than total color blindness, and there is no abnormality in vision or other complications of total color blindness. It is possible to distinguish objects when their colors are dark and bright; if the colors are light and unsaturated, it is difficult to distinguish and is rare.

The color vision disorder is lower than that of achromatopsia, and there is no abnormality in vision or other complications of achromatopsia.

6. Partial color blindness

There are red-green color weakness (first color weakness), green-green color weakness (second color weakness) and blue-yellow color weakness (third color weakness), among which red-green color weakness is more common. Patients have poor sensitivity to red and green. When the lighting is poor, their color discrimination ability is close to red-green color blindness; but when the color of the material is dark and bright and the lighting is good, their color discrimination ability is close to normal.