The Eye of Horus is an ancient Egyptian symbol of protection, royal power, and good health. The Eye of Horus is similar to the Eye of Ra (which belongs to a different god). Horus was the ancient Egyptian sky god who was usually depicted as a falcon. It was believed by the Greeks and Romans that an evil heart could get to the eye. The thought to be powerful effects of eyes and optics created the myth that the energy-producing power of the eye had the ability to cast evil spells with just a glance.
Also, this symbols used for mathematical purposes. The Rhind Mathematical Papyrus contains tables of "Horus Eye Fractions"