It is just not wise to look at bright light sources for prolonged time because the eyes are sure not replaceable
There are enough idiots in the world who damaged their retina by looking at the sun, and many HID lamps arcs are at about the same brightness.
It is not arc eye, as was said before. Until you are messing with germicidal or not UV-blocked pure quartz lamps, or arcs in the air, there is not much UV to cause this.
Arc eye hurts on the surface of the eyes (and skin) and is generally recoverable, at least if not extreme doses. But retina burns from lasers and sun are permanent.