The human eye is the most sophisticated camera in the world, so how far can it see?

Far visibility distance: 2× relative height of object (m)

A very simple eye structure can detect the boundary line between light and dark in the surrounding environment, and a more complicated eye structure can give visual effects. Compound eyes are generally found in arthropods (such as insects), and generally consist of many simple small holes, which create an image (not a multi-image as generally imagined).

People's eyes can often see distant objects clearly, because they can focus external light on their eyes. The length of all normal eyes is about 24mm, so many external light must be completely focused at such a short distance (24mm), which is mainly due to the strong focusing ability of the cornea. As mentioned earlier, the cornea has the focusing ability of 43 degrees.

when people's eyes change from far to near, they must not only adjust to make the light focus on the retina, but also turn their eyes inward so that the object under observation is on the visual axis. The process of turning eyes inward to make objects fall on the visual axis is called combination.

In many mammals and some coelenterates, both eyes develop by irradiating light to the retina, which is sensitive to light, where the light is received and converted into data signals and transmitted to the head according to nerve fibers. Generally, the eyes are spherical, filled with fully transparent solidified chemicals, with an eye lens for focusing and a retina that can adjust the amount of light entering the eyes.

To produce a clear image (focus) of something, the eyes must bend the light from the reflective surface of the object, so that the light immediately falls on the retina. Short-sighted people can only recognize short-distance objects, while long-distance objects look blurred, because the image is focused in front of the retina.

The way to correct this problem is to let people with myopia wear concave lenses, which will make the focused light fall back slightly and fall right on the retina. The factor of hyperopia is that the inner and outer diameters are shortened. The light from close objects is focused behind the retina, so it looks blurred, and only long-distance objects can see it clearly. Hyperopia patients should wear convex lens imaging to make the light slightly bend inward and help the light fall on the retina.