Looking at an arc welder is bad, it is a source that emits on a broad range of the electromagnetic spectrum. More specifically the blue and UV are particularly bad for vision:
Artificial sources of UV radiation also cause corneal damage. Injury from a welder's arc commonly is known as flash burn, welder's flash, or arc eye. Other sources of UV radiation injury include sun tanning beds, carbon arcs, photographic flood lamps, lightning, electric sparks, and halogen desk lamps. Several outbreaks of ultraviolet keratitis have been observed in the United States after installation of improper lighting in school gymnasiums, resulting in high levels of UV radiation.
Does lightning release the same magnitude of electromagnetic emissions as an arc wielder, in UVA, UVB or UVC spectra? Could watching lightning repeatedly degrade human vision?