That eye is Nazar (amulet.)
A nazar (Turkish: nazar boncuğu) is an eye-shaped amulet believed to protect against the evil eye ("evil eye", from nazar and "amulet" from boncuğu). The word "nazar" is derived from the Arabic نظر, "sight" or "seeing". In Central Asia, during the ages of Tengrism, people held similar superstitions like horseshoes, garlic, wolf's tooth, dried thorn, lead, stones; but the crystal blue eye has always been the most popular one.
It is common in Turkey, Syria, Lebanon, Egypt, Armenia, Iran, Afghanistan, Greece, Cyprus and Azerbaijan, where the nazar is often hung in homes, offices, cars, children's clothing, or incorporated in jewellery.
A typical nazar is made of handmade glass featuring concentric circles or teardrop shapes in dark blue, white, light blue and black, occasionally with a yellow/gold edge
The nazar image was used as a symbol on the tailfins of aeroplanes belonging to the private Turkish airline Fly Air. It is used in the logo for CryEngine 3, a game engine designed by Crytek, a video game company founded by three Turkish brothers.