Chris Harris wrote:

I don't know the current regulations. But the normal plastic lens used in
specs are almost bullet proof and used to be considered an acceptable
alternative, especially if side guards are fitted.

I had a accident a number of years ago while wearing standard
plastic-lensed specs.
One of the lenses shattered - the shards were long, thin, and very sharp,
and took a chunk out of my eyebrow, which needed a number of stitches to
repair - fortunately, the various bits of damage were just to my face,
narrowly missing the eye itself. Since then, I always get the most
impact-resistant lenses available. They cost quite a bit more, but I think
my sight is worth it.

Sheila