Rob Ventura explains in this video that when Christ states that He is the light of the world, it means that He dispels darkness and falsehood. It means that the light that Christ refers to is synonymous with truth.

John 8:12 (NKJV) - "Then Jesus spoke to them again, saying, 'I am the light of the world. He who follows Me shall not walk in darkness, but have the light of life.'"

So when Jesus speaks about being the light of the world, I believe the term light refers to being the truth of the world. The world is in darkness. Men are blind and bound and dead in trespasses and sins. Jesus says, whoever follows me shall never walk in darkness. Implication?

If we're not following Christ, we're walking in darkness. So that He's the light of the world, that means He dispels error, He dispels darkness. As we follow Him, we will always be in the light of God's truth and in the light of His Word.