An atlas of blinking across the species
 

Blinking played a key role in the emergence of vertebrates from the sea and in their adoption of a terrestrial lifestyle. The cornea has no blood vessels and its cells rely on oxygen diffusing from whatever medium the animal is in. Oxygen dissolved in water is able to enter the cornea down a partial pressure gradient. Atmospheric oxygen can only do this if the surface of the cornea is moist. Most fish have no need to moisten their corneas. Mud skippers, which spend much of their time out of the water, use all their extra-ocular muscles to pull the eye into head causing the cornea to brush against a stationary membrane which is kept moist with pooled sea water. Longer established terrestrial vertebrates have evolved a number of structures which moisten the cornea though the process of blinking. These include upper and lower eyelids, a nictitating membrane and a retractor bulbi muscle to pull the eyeball into the skull. Some have evolved these structures only to do away with them later on in their evolution.
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This website shows, through videos, stills and drawings, how blinking has diversified across the species. It is seen from the viewpoint of a neurologist with a particular interest in movement disorders including eye movements.