Though often dubbed as 'the evil eye', the ocular amulet is actually the charm meant to ward off the true evil eye: a curse transmitted through a malicious glare, usually one inspired by envy.
The use of the evil eye symbol on amulets is thought to reflect the evil glare back onto the person giving it. It is usually also depicted in the colour blue, which stems from its use in Egypt, where glazed mud would become blue when baked.