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The mysterious root of night blindness: Why can't we see in the dark?
Night blindness, also known as nyctalopia, is a condition in which it is difficult or impossible to see in relatively low light levels, which can be caused by a variety of eye diseases. Night blindness can be present from birth or can be caused by injury or poor nutrition (such as a lack of vitamin A). This condition can be described as a lack of adaptation to darkness, which makes it challenging for patients to function during the twilight hours.
The most common cause of night blindness is retinitis pigmentosa, an inherited disease in which a person's rod cells gradually lose the ability to respond to light.
The retina is the cell at the back of the eye that senses light. Rod cells are dedicated to helping us see in low-light environments, and when these cells are damaged, night blindness results. This condition may worsen over time, eventually affecting daytime vision as well.
In addition to developmental causes, night blindness can also be caused by a deficiency in vitamin A, an important nutrient found in fish oil, liver and dairy products. Vitamin A deficiency can lead to visual adaptation disorders, affecting vision at night or in dark environments.
Healthy eyes depend on the release of a special visual pigment called rhodopsin, a protein that is responsible for allowing us to see in the dark.
When light enters the eye and hits rhodopsin, it goes through a series of changes that ultimately create an electrical signal that is transmitted by the optic nerve to the brain. However, in the absence of light, rhodopsin takes time to regenerate. Therefore, when a night blind person moves from a bright to a dim environment, the time it takes for the eyes to adjust is significantly prolonged.
Other potential causes of night blindness include cataracts, glaucoma, and certain medications (such as phenylthiazides). For some people, this can be due to different conditions of the retina, such as retinal detachment and retinopathy. Regardless of the cause, patients may experience significant vision loss.
From a historical perspective, the ancient Roman physician Aulus Cornelius Celsus described night blindness around 30 AD and recommended dietary improvements, especially emphasizing the liver. As an excellent source of Vitamin A.
"Besides a certain weakness of the eyes, the people could see fairly well during the day, but were completely blind at night."
The condition was also documented during the American Civil War, particularly in the Confederate states. At the time, many people were skeptical of the disease, thinking it might be a fake or exaggerated condition. Under these circumstances, many soldiers reported night blindness, accompanied by symptoms of scurvy.
Night blindness exists not only in humans, but also in animals. Taking horses as an example, congenital stationary night blindness associated with spot pattern is an eye disease in horses that affects vision in low-light environments. The disease is linked to a genetic variation in horses and is closely associated with their color pattern.
Genetic research has found that the gene TRPM1, which is related to night blindness, may affect the basic chemical reactions of animal vision and the transmission of nerve impulses. This shows that night blindness is not just a health problem for humans, but also covers the health maintenance of animals.
Finally, night blindness, as a symptom that affects vision, makes us reflect on the close connection between physical health and lifestyle habits. Faced with this mysterious situation, we can't help but ask: Perhaps in modern society, we should pay more attention to the health of our eyes and the intake of vitamin A in our diet?
