Why are the eyes of animals glowing under the lights?

In the dark night, if you accidentally hold the flashlight and direct it into the eyes of a dog or a cat, you will be quite surprised when their eyes glow. So why do eyes of animals like dogs, cats, . have this special ability and human eyes?

The reason for the bright eyes typical of dogs, wolves, North American pandas, crocodiles and many other species is due to "tapetum lucidum" - a cell layer that acts like a mirror behind the retina. This structure is found mainly in nocturnal animals, acting as a light amplifier. Often, the retina takes part of the light into the eye, but lets another part pass through. The tapetum lucidum mirror will reflect this pass through the retina, giving the animal a chance to "see" it a second time. It is this light that has sparked many horrifying horror stories for superstitious people.

So what about people? What is the ability of people to see in the dark? As you know, cats are better adapted to us in low light conditions. They have a larger cornea and pupil of humans, so getting more light in low light conditions. They also have a tapetum mirror that helps reflect light back to the eye. In this way, their retina has 2 opportunities to access the same photon of light.Tapetum of cat's eyes reflects light 130 times, stronger than human eyes. That's why the cat's eyes glow in the dark on the photos.

Reading here, you can be proud that although people are not animals that look in the dark, we must have the best day vision. However, in this case, we are far behind the eagle. Eagle eyes have the same size and weight as human eyes. But they have a different shape. Behind the eyes they are flatter and wider than our eyes, giving it a much larger field of observation.

Behind the human eye is a special area in the retina called fovea , which has a large density of visual cells . Fovea has about 200,000 cones per millimeter, an amazing number. But it has not been absorbed in comparison with the eagle. Their fovea has about 1 million cones per millimeter. It allowed the eagle to see a mouse 1.6 km away. That is far beyond human ability.