It is no different with the eyes of the heart. Having a simple figurative eye means that we are single - minded in purpose.
فَٱلْعَيْنُ ٱلْبَسِيطَةُ هِيَ ٱلْعَيْنُ ٱلْمُرَكَّزَةُ عَلَى هَدَفٍ وَاحِدٍ .‏