Does a laser beam have to hit the eyes in order to damage them? Or can a person's eyes get damaged by looking at a beam that goes past their eyes (e.g. looking at a laser beam moving inside an enclosure)? If just looking at a beam that goes past a person can damage the eyes, What factors would affect whether it is potentially dangerous? (like how strong would the beam have to be and how long would a person have to keep looking at it?)