Wholeness of Vision

The audience of the New Testament understood the eyes to see through what Plato called Emission Theory. That is, that light comes from the eyes and illuminates what you are looking at. Therefore, they defined light as unobstructed vision and dark as obstructed vision, but it was all based on the idea of where the light of vision comes from. That being said, what is the New Testament telling us when it continually contrasts light and dark?