I think what arcab means that black light in general is bad for eyes for just looking at it. Sun light is not bad unless you look directly at the sun. Permament damage will result around 40 seconds. When I was in school, I was told never to look at an eclipse. Nobody really knew why. I did however find an answer. Even though the sun is mostly cover by the moon, just 4% of the sun can cause harm to your eyes. But sun light in general does not cause harm as black light may.