I have a friend who puts together adaptive computer systems for the disabled. He has a large population of folks who have lost central vision and have only peripheral after industrial accidents involving the eyes.
Did some "research" if you can call it that. It was really just noodling around on the internet and looking at different posts on websites with some technical info from professional publications. It seems that welding was invented first, and eye protection came afterwards. It's not clear how many people lost their eyesight during the learning curve but it appears their may have been some casualties. Eye injuries are to the cornea and the retina. Lots of technical stuff about ultraviolet and blue spectrum vs some other spectrum but it seems that any eye protection of even a clear lens gives some protection against uv light. In an industrial setting, second hand exposure from peripheral sources can be harmful so welding is done is booths with curtains when possible and eye protection is always required for other workers or visitors. And apparently duration of exposure is a factor. So one can be exposed to flashes if they are of short duration. However, damage can be cumulative.
This demystifies auto darks for me. It seems the milisecond of exposure to the flash is considered "safe". Plus there is at least a clear lens in place which offers a degree of protection.
Higher quality helmets have four sensors to insure good performance. Poor quality have fewer. Some can malfunction and one will get a flash exposure. Battery can go dead or they can just fail to operate. It appears some weldors love them and some not so much. Some guys have flashed themselves more frequently with fixed type when they accidentally strike an arc or forget to put their helmet down.
Be careful. Welding is dangerous. We only have one set of eyes.
