In addition, there is the whole matter of light and shadow as used by artists in paintings to give an illusion of reality. As an asside, the only explanation of drawing with light and shadow that I ever understood was in a manual written by Leonardo da Vinci. His exposition was clearer than anything I've seen since. Like every other technical innovation concering blindness, all this is to point up just that such instruments have their limitations. Just one person's opinion.
Innovation is hard to schedule.