I believe this scripture is dealing with the things we set our eyes on. By setting our sights on what is ungodly, we allow darkness to enter our hearts. By setting our eyes on the things of our Lord, we receive light.
Here are some scriptures that I feel support this view:
"For he was looking forward to the city that has foundations, whose designer and builder is God" (Hebrews 11:10 ESV).
"If then you have been raised with Christ, seek the things that are above, where Christ is, seated at the right hand of God. Set your minds on things that are above, not on things that are on earth. For you have died, and your life is hidden with Christ in God. When Christ who is your life appears, then you also will appear with him in glory" (Colossians 3:1-4 ESV).