How do eyes see things? Is what we see reflected?

Seeing an object requires a series of complex neural reactions, among which the macula on the retina is the most sensitive area of the human eye to light. When we want to see things clearly, we need to focus the image on the macula. Focusing on other places can only make us have a blurred effect. There is a disease called macular degeneration, which can lead to blindness in severe cases. Even if the light is focused on the retina correctly, but the corresponding neurons no longer respond to the light, then we can't see the world. You can think of macula as a negative of a traditional camera or a photosensitive CCD in a digital camera. If something goes wrong with this thing, then you can't see anything. Focusing light on the retina is the basis of our vision and the most prone to problems, so we have myopia, hyperopia and astigmatism.

The formation of vision needs the close cooperation of several links, and any obstacle in any link will lead to visual impairment or even blindness. Therefore, it is very important to protect your eyes, especially when you watch your mobile phone for a long time. You need to learn the skills of active blinking, eat more foods rich in carotene or vitamin A in your daily diet, and control yourself not to rub your eyes casually. Don't do so-called eye exercises that damage people's eyes, it's useless, and it will increase the risk of eye infection. The human eye is a delicate camera, and its lens is equivalent to a convex lens. When the distance from the object to the convex lens is more than twice the focal length, the convex lens becomes an inverted and reduced real image, and the camera is made according to this principle.

When the convex lens becomes a real image, the object distance decreases and the image distance increases. Therefore, it is necessary to adjust the position of the light screen to accept images of objects at different distances. The distance from the retina to the lens of the eye is certain, but the focal length of the lens of the eye can be adjusted by the ciliary muscle. When looking at the near object, the ciliary muscle contracts, which makes the lens thicker, the focal length smaller, and the convergence ability enhanced, so that the image of the near object changes on the retina. When looking at distant objects, the ciliary muscle relaxes, the lens becomes thinner, the focal length becomes larger, and the convergence ability is weakened, so that the image of distant objects becomes on the retina.