LUKE 10: 34-36
The lamp of the body is the eye. Therefore, when your eye is good, your whole body also is full of light. But when your eye is bad, your body also is full of darkness.Therefore take heed that the light which is in you is not darkness.
If then your whole body is full of light, having no part dark, the whole body will be full of light, as when the bright shining of a lamp gives you light.”
Jesus was simply illustrating, we can have different types of light .
Light that will illuminate light or light that is darkness.
This is determined by what we expose ourselves to,if we expose ourselves to things that edify us as the body of Christ, we illuminate the light of Christ through us, however if we expose ourselves to the things of this world, we illuminate light which is darkness.