I work in a field where we are continually concerned with filtering light emissions (flameworking glass), but I don’t know the answer to that, either, whether visible light can cause permanent damage.

I do know that infrared can cause serious problems, such as burns and perhaps macular degeneration. It is mainly what welding shades and our glassblowing glasses filter.

^ I should have noted that welding shades and glassblowing glasses also filter visible light heavily, of course (>90%). But what distinguishes them from sunglasses is the IR filtration. Glassblowing lenses also filter sodium flare, a glaring orange (visible) light emitted by some glass in a flame.

IR drops off adequately at spectating distances, and when I am at a demo, watching other people work, I don’t wear my glasses. Not sure about at a nuclear blast though.

Feynman also advocated for not brushing your teeth. He wasn't really any kind of health expert.

And even if he reasoned UV light wouldn't hurt him, he still had to duck to avoid the exposure. So if there's anything to take away from his story it's that he didn't know what he was talking about.

That’s a good point. Maybe the temporary afterimage was the worst that could have happened to me.