Eye Spy

How is it that some animals are able to see in the dark? The most interesting feature of nocturnal animals is the size of their eyes. Large eyes, with a wider pupil, larger lens and increased retinal surface collect more light. Some animals of the night have acquired a spherical lens and widened cornea to compensate for reduced eye movement. This combined with a wide cornea increases the animal’s field of view allowing the head and eyes to remain motionless. Some animals have eyes that glow in the dark. This is due to the tapetum lucidum an adaptation for night vision. The tapetum is a thick reflective membrane, directly beneath the retina. It collects and re-emits light back to the retina a second time, giving the rods a second chance to absorb the image information, thus maximizing the little light available to them. Although nocturnal animals see mostly crude or imperfect shapes, outlines and no colours, by maximizing their sensitivity to low light levels with the above adaptations, it is enough for them to hunt, feed and survive in the dark of night.