Complex sentence: Although the size of the eagle eye is about the same as of a human being, the back side shape of the eagle eye is flatter; it has larger vision and its retina is more pronounced with rod cells and cone cells.
Split into simpler sentences: Although the size of the eagle eye is about the same as of a human being, the back side shape of the eagle eye is flatter. Its retina is more pronounced with rod cells and cone cells.