Green blindness

Introduction Green blindness, also known as second color blindness, does not distinguish between light green and dark red, purple and blue, purple, and gray, with green as gray or dark black. Since the patient has no normal color discrimination ability since childhood, the color can be distinguished according to the intensity of the luminosity, so it is not easy to be found. Red-green blindness is one of the most common human sexual genetic diseases. 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.

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.

The corresponding diseased organ is the eye, the detailed point is the retina, and then the cone is detailed. Cone cell: The morphology of the cells is similar to that of rod cells. The cone cell body is located in the outer part of the outer nuclear layer, the cell nucleus is larger, and the staining is shallower. The cone is also divided into an inner section and an outer section. Most of the outer membrane discs are not separated from the cell membrane, and the top membrane disc does not fall off. The membrane disc is embedded with visual pigments that can sense strong light and color vision, and is continuously synthesized and supplemented by the inner segment. Humans and most mammals have three kinds of cones, including red-sensitive pigment and blue; blue-sensitive and green-sensitive pigments, which are also composed of 11-cis-retinal and opsin, but the structure and rod of opsin The difference in cells. If there is a lack of cones that are red (or green), the red (or green) color cannot be distinguished, and the red (or green) color is blind. The condylar end of the cone is swollen to form a synapse with dendrites of one or more bipolar cells and horizontal cells.

There are about 120 million rod cells and 7 million cones in one eye. In the fovea of the macula, there are only cone cells, no rod cells, and the rod cells begin to appear at the edge of the fovea. Later, the rod cells gradually increase, and the cone cells gradually decrease.

an examination

Related inspection

Eye and sacral area CT examination Farnsworth 15 color standard test FM-100 color test Nagel color vision examination method subjective inspection

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.

How to determine color blindness and color weakness: Color blindness and color weakness are mostly checked by subjective inspection, generally in brighter natural light. The commonly used inspection methods are as follows.

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.

Color blindness is divided into full color blindness and partial color blindness (red blindness, green blindness, blue-yellow blindness, etc.). Color weakness includes weak color and partial color weakness (red weak, green weak, blue-yellow weak, etc.).

Differential diagnosis

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. Blue and yellow blind

Also known as the third color blindness. The patient's blue-yellow color is unclear and is identifiable to red and green.

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.

5. Partially weak

There are red weak (first color weak), green weak (second color weak) and blue yellow weak (third color weak), among which red and green are weaker, patients are less sensitive to red and green, and when lighting is poor, The color ability is close to red-green blindness; but when the material color is dark, clear and the illumination is good, its color discrimination ability is close to normal. 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.

The material in this site is intended to be of general informational use and is not intended to constitute medical advice, probable diagnosis, or recommended treatments.