Light is the ultimate ideal in ancient Hebrew philosophy, representing both knowledge and morality. When someone is spiritually blind, they reject God, making it impossible for them to discern His truth. The reference to light describes how Christ will be the messenger of the gospel up until His death and resurrection when His apostles and disciples will become the "lights" of truth for this world.
During His time on earth, the Lord Jesus was the light of the world. In essence, he was the true light from heaven. All who enter the world receive light from him because he was the light. It was He who shed the warmth of His love and light into the broken hearts of many. It was his healing light that radiated into the lives of those whose bodies were broken and whose minds were disturbed. For all who put their trust in His name for salvation, He shined His redeeming light into their hearts and lives.
God is light, an unapproachable light. Nevertheless, His Spirit of light has been placed within our hearts to guide us into all truth and to bring His love to those with whom we come into contact.

Dear Heavenly Father, it is Your grace that has lifted me out of the kingdom of darkness and into the glorious kingdom of light. Help me not only to understand Your will but also to obey it joyfully and expectantly. Thank You for forgiving me for being reluctant to obey when I don't fully understand why You want me to do something. I pray that Your love and grace shine through me so that I can reflect the true light that illuminates all who come into this world. 
In Jesus's name I pray. Amen.