I was welding heavy current under large assembly, flipped up hood to look at weld, and as I moved position caught a big flash as rod stuck arc up close to where I was looking. Initially just unable to see properly out of one eye, residual image of teh flash ... carried on work .. then feeling of sand in the eye, and that got worse & worse ... intensely painful.
Whether it's the intent flash, up close, high current ......... but I would NEVER arc weld without a shield .... EVER.
Illogical and senseless to do so, the intense UV alone is bad enough.