Tapetum lucidum

tapetum lucidum /tə-pē'təm 'lü-si-dəm/ noun: a membrane behind the retina of many animals responsible for improving vision in low-light conditions by reflecting received light back through the retina, making it available to photorecptors

Etymology: Latin tapetum lucidum bright tapestry

Three notes on the tapetum lucidum:
• Humans do not have tapeta lucida, but cats and dogs do. That’s why your pet gives you that creepy eyeshine when you catch its stare at the proper angle.
• Whereas the night vision of animals possessing tapeta lucida is better than that of those who do not, that vision comes at the price of clarity; all that light bouncing back inside the eyeball blurs the edges of perceived images.
• I dissected a cow eye several years ago. Its tapetum lucidum possessed a beautiful, metallic, bluish iridescence. (Don’t ask me what a cow — a diurnal creature — was doing with a tapetum lucidum. But sure enough, there it was when I sliced away.)