The eye is the lamp of the body. So, if your eye is healthy, your whole body will be full of light, but if your eye is bad, your whole body will be full of darkness. If then the light in you is darkness, how great is the darkness!
I have heard it said that we are what we gaze upon. This statement makes us feel a bit uncomfortable. We all watch stuff in movies and on TV that are pretty dark. Even news shows are often full of darkness. The culture is full of dark images and pictures that we have a hard time avoiding and sometimes it is a challenge to find positive ones to gaze upon.
Jesus speaks to this telling us to keep our eyes healthy. The idea is to gaze upon things that embody goodness and stay away from evil images. I could wax on with examples of visual things that are bad but I think that lists of things holy and unholy are not always helpful. Better that we learn to listen to that inner voice. God is there to help us.
Lord, help me to listen to your voice as you instruct me on the things that please to you.