Safety Glasses 99.9% UV protection
External Clear lens 99.9% UV protection
Auto Dark lens (working or not) 99.9% UV protection or a standard fixed lens
Internal Clear lens 99.9 UV protection
Cheater Lens 99.9 UV protection.
4 or 5 layers of UV eye protection we are talking about here.
This is what you get with an auto dark or a fixed lens welding hood setup.
Nobody is getting hurt if either are being worn.
If the battery is low or the sensors are covered on an auto dark helmet, it may be a bit annoying to get a bright flash at the normal #5 shade but no damage is being done.
My only suggestion for new students is that they spend the money for an auto dark hood with multiple shades so they can be comfortable with high and low amperage operations.
Auto dark lenses shorten the learning curve for beginners by a large margin. Seeing where to begin is one of the most important parts of learning to weld.
Having said that I prefer my old vulcanized Huntsman most of the time. But I did break down and get an auto hood and for the most part I like it.
Edit:
What about the bright light?
What does AWS say about all this?
Safety and Health Fact Sheet No. 26 http://www.aws.org/technical/facts/FACT-26.pdf"Retinal Exposure
In addition to actinic UVR measurements,
another study was published as a
USAEHA report (Ref. 7) in 1977 containing
an evaluation of potential retinal
exposure hazards. The eye can focus an
open arc onto the retina where an injury
might result that was photochemical or
thermal in nature. Photochemical injury
is the result of exposure to intense blue
light sources, whereas thermal injury can
result from all visible and some near-infrared
radiation, which is largely invisible.
Measurements of blue light and
other retinal-thermal emissions suggest
momentary viewing of electric welding
and cutting arcs does not exceed retinal
exposure limits; however, staring at an
open arc can readily exceed these standards.
While staring at the arc should
never be permitted, actual retinal injuries
are rare (Ref. 8) and would likely result
only from chronic staring."