Frog Eye (40x Magnification)
Frogs have eyes that closely coordinate with their long sticky tongues to enable these amphibians to capture fast moving prey with whip-like accuracy. A majority of species possess eyes that bulge from the sides of their heads so that most frogs can see in almost all directions. However, frogs are naturally nearsighted and are only able to focus on objects that are passing close by or flying within a distance of six inches. Frogs reduce the amount of light that enters their eyes by closing their pupils into narrow slits. Although they have protective clear membranes that can cover the eye surface (termed the cornea) these creatures have poorly developed eyelids that do not close during resting periods. Instead, frogs typically withdraw their eyes into sockets located within their skulls. Frogs also use their eyeballs to help push food down their throats by retracting each eye, usually one at a time, into the sockets.