Blue-yellow blindness

Introduction The patient's blue-yellow color is unclear and is identifiable to red and green. People with blue-yellow color blindness are difficult to recognize blue and yellow. Blue-yellow blindness includes blue blind (tritanopia, third color blindness) and blue weak (tritanomaly, third color weak). Blue-yellow blindness is one of color blindness.

Cause

Since the patient does not have normal color discrimination ability since childhood, it is not easy to be found. It is generally believed that red-green blindness is determined by two pairs of genes on the X chromosome, namely the red blind gene and the green blind gene. Since these two pairs of genes are closely linked on the X chromosome, they are often represented by a gene symbol. The genetic pattern of red-green blindness is X-linked recessive inheritance. Men have only one X chromosome, so they only need a color-blind gene to perform well. Women have two X chromosomes, so they need to have a pair of pathogenic alleles to behave abnormally. If a normal woman marries a color-blind male, the father's color-blind gene can be passed to their daughter along with the X chromosome and cannot be passed on to the son. The daughter passed the color blind gene from her father to her son. This phenomenon is called cross-genesis. Thus there are far more male patients than female patients.

an examination

Related inspection

Ophthalmic examination ophthalmoscopy

Color blind (weak) patients are born with no correct color discrimination ability, and think that others are the same as themselves, so they can not be consciously sick, and many color blind patients have no abnormal findings in eye examination.

False homochromatic map: commonly referred to as a color-blind book, which uses dots of the same shade and different colors to form numbers or figures, and reads at a distance of 0.5 m under natural light. The color blindness should be corrected when checking, and each figure should not exceed 5 seconds. Color vision disorders are difficult to identify, misread or impossible to read, and can be confirmed according to the color blindness table.

Color Harness Test: It is a mixture of different shades of yarns of different colors, so that the examinee picks out the same color bundle as the standard harness. This method is quite time consuming and can only be qualitatively and cannot be quantified, and is not suitable for large-area screening tests.

Color Mixing Tester: It is a kind of spectrometer designed by nagel based on the principle of red + green = yellow. It can quantitatively record the amount of red and green light matching to determine the red and green anomaly. This method can be qualitative. It can be quantified.

Differential diagnosis

Differential diagnosis of blue-yellow blindness:

Full color blindness

It belongs to complete cone dysfunction, which is the opposite of night blindness (rod cell dysfunction). Patients are especially dark and photophobic. The colorful world is gray in its eyes, just like watching black and white TV, only the distinction between light and dark, and no color difference. Moreover, the red color is dark, the blue light is bright, and there are symptoms such as poor vision, amblyopia, central dark spots, and oscillating nystagmus. It is the most serious type of color vision disorder and is less common in patients.

2. Red blindness

Also known as the first color blindness. The patient is mainly unable to distinguish red, and cannot distinguish between red and dark green, blue and purple, and purple. Often, green is considered yellow, purple is seen as blue, and green and blue are mixed into white. There was a veteran middle-aged man who bought a gray sweater and put it on to ridicule him. He turned out to be a red blind patient, and his red color was gray. In the early years, there was a report that a red blind patient became a train driver and the train collided because of the wrong signal.

3. Green blindness

Also known as the second color blind, the patient cannot distinguish between light green and deep red, purple and blue, purple and gray, and green as gray or dark black. There is a well-painted child in an art training class. The sun is always painted green, the crown and the grass are painted brown. It turns out that he is a green blind patient. Clinically, red blindness and green blindness are called red-green blindness, and patients are more common. The color blindness we usually say is generally red and green blind.

4. Full color weakness

Also known as red, green, blue and yellow. The color vision disorder is lower than the full color blindness, there is no abnormality in visual acuity, and there are no other complications of full color blindness. When the object is dark and vivid, it can be distinguished; if the color is shallow and not saturated, it is difficult to distinguish. Patients are also rare.

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