"The problem is that both light we can see and light we can not see have the potential to damage our eyes. Visible light is like the colors of the rainbow, while invisible light is called "ultraviolet light" (uv rays) and while it can't be seen can still wreak havoc with our eyes. Too much of the wrong kind of light can lead to cataracts, macular degeneration, or, sometimes, melanoma around the eyelids."