We love them and pet them but when we try to take pictures, their eyes become tiny torch-lights and our well known pets look very fierce and alien to us. Dogs, just like cats and horses, have the ability to see in the dark and when a light is flashed on their eyes in the dark it starts to glow bright. The gleam in the eyes of the dogs is a natural phenomenon. They are natural hunters and hunt at night. It might seem eerie or even scary to you but the burning eyes of your dogs are just normal. Science explains the glowing dog-eyes perfectly.
Between the optic nerve and the retina of dogs there is a reflective surface named tapetum lucidum. The tapetum lucidum is responsible for the glow we spot in the eyes of our furry pets. You will probably feel relieved to know that other nocturnal animals like deer and horses also have glowing eyes. Humans do not have tapetum lucidum because we are daytime hunters and does not need to see in the darkness though it would have been super cool to be able to see in pitch black darkness like our dogs.
The light reflects from the tapetum lucidum and fall on the surface of the retina, enabling the dogs to see through the darkness. In dim light often the photoreceptors in the eyes fail to perceive the light and cannot send signals to the brain. As a result we cannot see in the dark. But due to the presence of the tapetum lucidum layer of cells even little amount of light gets reflected and bounced back to the retina and can be perceived easily. The reflection of light within the eyes makes the eyes of the dogs glow in the dark.