RA had two eyes surprising as that may seem to some, they related to the planets of inferior orbit Venus and Mercury as closely related too and extensions of the power of the Sun.
Hathor represented Venus as an eye of RA and Horus the Falcon represented Mercury as the other eye of RA, the eye seen in Free Masonry for example is obviously the eye of Falcon Horus.
Horus himself was understood to have both a solar and lunar eye.