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Comment by knifie_spoonie | Hacker News Reader

Wearing sunglasses apparently helps. You just need to make sure they have a proper UV rating, a lot of the cheap ones you get online don't do a good job of blocking UV.

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Years ago I saw on TV a report where people bought several sunglasses sold in the street in Brazil and compared to the expensive brands and they all cut UV quite effectively.

Not that I would trust national TV test methodologies and risk my vision but it was a curious result.

Off topic but in the same vein: https://en.wikipedia.org/wiki/Judgment_of_Paris_(wine)

Those that fail to block uv can leave your eyes exposed to more UV than if you were not wearing any sun glasses.

My layperson understanding is this happens because the mechanism that dilates the pupil responds to visible light so glasses cause it to open wider, but if they don’t block UV then you end up with more UV exposure than if you didn’t wear anything

I find that surprising since most plastics you would make glasses from should block uv.

Most plastics are transparent to UVA, which is like 90% of UV that reaches earth's surface. They only start absorbing at higher UV frequencies. That's why sunglasses have dedicated UV ratings. You can bring your sunglasses to basically any optometrist and test how well they block UV. It takes 20 seconds and they'll probably do it for free.

That makes sense, thanks.

Glass protects from UV bellow 350nm, which leaves 350nm-400nm band open. So additional coating is required. I might be wrong but such factors as glass thickness and the radiation intensity should be also accounted for. Every physical object is mostly an empty space ...

Visual range goes to 380. I'm skeptical that light at 350 is really doing much damage to my eyes.

It actually does not not matter what you see. You can't see UV, and it harms your eyes. What you need is a protection from UV band, and that is exactly what your eye can't see.

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