Monkey have a special, reflective surface right behind their retinas called the tapetum lucidum, helps animals see better in the dark.
When light enters the eye, it hit a photoreceptor that transmits the information to the brai. But sometimes the light doesn't hit the photoreceptor, so the tapetum lucidum acts as a mirror to bounce it back for a second chance.
A large number of animals have the tapetum lucidum, including deer, dogs, cats, cattle, horses and ferrets. Humans don't, have tapetum lucidum so our eyes don't shine.