How do your eyes adapt to the darkness
Poor eyesight in the dark
“I hate to drive in the evening. I am night blind ”. Everyone has probably heard this sentence before. In fact, most people see worse at night. The cause of this is only in the rarest of cases night blindness, explains Prof. Dr. Horst Helbig from the professional association of ophthalmologists. On the one hand, the supposed visual difficulties are caused by the way the eyes work. On the other hand, existing visual defects are more pronounced in the dark.
At night all cats are grey
The retina of the eye has two different sensory cells: uvula and rods. The suppositories in particular work in daylight. They specialize in color vision and convey a colorful picture of the world. At dusk, the rods dominate the visual process. They are experts in dark vision and distinguish between the finest nuances of brightness. Chopsticks immerse the world in a sea of different shades of gray and blue. This confirms the old adage that all cats are gray at night. So if you can see through a gray veil at dusk, you don't have to worry about being night blind. Rather, he can be amazed to see the multitude of gray tones with which his nocturnal rods react to the different levels of brightness in the environment.
Darkness increases existing visual difficulties
Often the gray veil is not the only strange visual phenomenon in the dark. Contours are blurred, a rainbow-like, diffuse halo of rays surrounds light sources and sudden incursions of light blind the eyes painfully. These types of vision problems indicate existing eye diseases. They are especially useful when the pupil dilates in the dark so that more light penetrates to the retina. "In poor light conditions, small visual defects are more noticeable that we do not even notice in the light" reports Prof. Dr. Helbig. “Because with a wide pupil, such visual defects have a stronger effect.” For example, a rainbow-like halo of rays speaks for myopia. Increased sensitivity to glare in the dark is a symptom of cataracts.
Night blindness is very rare in developed countries
In the case of real night blindness, the rods do not adequately adapt to the changed light conditions during the transition from light to dark. As a result, those affected have serious difficulties in finding their way around in the dark. Most of the time the disease is hereditary. Night blindness also occurs when the rods do not have enough vitamin A available to regenerate their visual pigment. The population of the rich industrial nations is hardly affected by this form of acquired night blindness. Most of the time, she manages to meet her daily vitamin A requirement of 1-2 mg from carrots, kale, spinach, liver, milk and eggs. However, a sufficient supply of vitamin A is not guaranteed for people who suffer from chronic gastrointestinal diseases or who take certain drugs for weight loss.
AuthorsSusanne Schmid / Professional Association of Ophthalmologists in Germany | last changed on at 12:40
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