How are our eyes protected?
Our eyelids snap shut when something moves suddenly in front of our eyes. This swift reflex is the body's way of protecting the eyes from injury.
Animals too, protect their eyes in many different ways. Most birds have three eyelids. The third eyelid is a semitransparent tissue, called the nictitating membrane.
In water birds, the third eyelid has a clear, goggle-like lens which improves the ability of the eye to focus under water. Birds also have long thin feathers over their eyes that act as eyelashes to keep out dust.
Desert animals too, have long eyelashes for protection against sand storms. Snakes and fish have no eyelids- their eyes are protected by a glassy coating.
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