Have you ever wished you could see in the dark as well as an animal? In action movies, we often see characters wearing special glasses that reveal(显示)things that can't be seen in darkness. Everything looks green, but we can see the shapes and outlines clearly. As a matter of fact, this is somewhat similar to the way animals' night vision (视力) works.
You may have noticed eyeshine in pictures of animals, or seen it for yourself when light hits an animal's eyes. Dogs, cats, and many other animals have tissue (组织) called the tapetum lucidum(光神经纤维层) in each eye. The purpose of this tissue is reflect (反射) light deeper into the eye. For many animals, it leads to their excellent night vision, and it helps them hunt.
Different types of animals have different colors of eyeshine. The light reflecting back from the eyes of dogs and cat is likely to be yellow. Rats and birds usually have eyes that shine red. Other animals' eyes may reflect white, yellow, green, or pink light. In each case, the color is related to the type of cells that make up the tapetum lucidum, as well as the chemicals inside the cells.
Eyeshine has the function of improving animals' night vision, but humans have found other uses for it. For example, when people are searching for certain types of animals, their eyeshine may be helpful in recognizing or discovering them. Also, eyeshine has inspired humans to invent substance (物质) that reflect light at night. Strips containing this substance are used to warn us of safety risks such as raised parts of roads. Even though humans cannot see so well at night, we have still found ways to benefit from this amazing animal feature.