In contemplating vision today, I am drawn to a scripture at the beginning of the Doctrine and Covenants. This is a famous missionary scripture. It was first given as a revelation for Joseph Smith Sr. by the prophet: And faith, hope, charity and love, with an eye single to the glory of God, qualify him for the work. An eye single to the glory of God is vitally important. (D&C 4)
Vision can be obstructed, but other things which might be in the way, a tree or something. In like mode, if we put a hand in front of our face, we cannot see.
The Sermon on the Mount teaches us that the light of the body is the eye. The scriptures also teach that the foolish have eyes but see not. God is not talking about our physical eyes, but our spiritual eyes. Our focus, our spirit, must be focused on God. We cannot let obstacles in the way. If there are obstacles we must remove them.