Eyes of Understanding is that point where once the darkness shielded your will and mind from comprehending what is before you. Here, those in darkness; i.e. do not know our God and Father nor his Only begotten Son Jesus Christ need to have spiritual Revelation from the Spirit of God. Just as the Apostle Paul who consented to the death of martyr Steven, but later on the way to Damascus received a vision that revealed the truth. He thus, followed the Way of those he persecuted. Many today experience this!