Some fish, as with some amphibians, have the ability to thrust their eyes down into their eye sockets to aid in pushing food down their throats. Sharks have a protective membrane which covers the eye at the moment of striking to reduce damage risks to their eyes. Some benthic fish have adipose eyelids. Their function is not completely understood. The most popular theory is that since bentic fish live in perpetual darkness, the translucent eyelids may be employed as light wavelength filters to help the wide pupils make sense of their surroundings when they venture up the water column towards lighted areas.