Frogs can close their eyes by pulling the eyeballs deeper into their sockets. This action closes the upper and lower eyelids. Most species also have a thin, partly clear inner eyelid attached to the bottom lid. This inner eyelid, called the nictitating membrane, can be moved upward when a frog's eyes are open. It protects the eyes without completely cutting off vision.
Most frogs have a disk of skin behind each eye.
Each disk is called a tympanum, or eardrum. Sound waves cause the eardrums to vibrate. The vibrations travel to the inner ear, which is connected by nerves to the hearing centers of the brain. Most frogs have a delicate sense of touch. It is particularly well developed in species that live in water.