Why are a cat's eyes glowing green? - briefly
A cat's eyes glow green due to the tapetum lucidum, a reflective layer behind the retina that enhances night vision by reflecting light back through the retina.
Why are a cat's eyes glowing green? - in detail
The phenomenon of a cat’s eyes glowing green is a fascinating result of their unique anatomical and physiological adaptations, specifically the presence of a structure called the tapetum lucidum. This layer of tissue is located behind the retina and acts as a reflective surface, enhancing a cat’s ability to see in low-light conditions. When light enters a cat’s eye, it passes through the retina, where some of it is absorbed by photoreceptor cells. However, any light that is not absorbed reflects off the tapetum lucidum and passes through the retina a second time, effectively amplifying the available light and improving night vision. The green glow observed in a cat’s eyes is the result of this reflected light, which is filtered through the tapetum lucidum’s specific pigmentation. The tapetum lucidum in cats often contains zinc or riboflavin, which contribute to the greenish hue of the reflected light. This adaptation is particularly advantageous for cats, as they are crepuscular hunters, most active during dawn and dusk when light levels are low. The green glow is most noticeable when a light source, such as a flashlight or car headlights, shines directly into a cat’s eyes in the dark, causing the tapetum lucidum to reflect the light back. This glowing effect is not unique to cats but is also observed in other nocturnal and crepuscular animals, though the color of the glow can vary depending on the species and the specific composition of their tapetum lucidum. In cats, the green glow is a direct consequence of their evolutionary adaptation to optimize vision in dim environments, ensuring their survival and effectiveness as predators.