Muppet, I believe that on the bbc "have your say" thing about this issue there was someone claiming an eye injury through a conker game.

I would suspet that the risks are low with conkers and think that sort of precaution (outside possible litigation) OTT but conkers can smash and there is no telling where the bits may land and eyes are vulnerable.

I have a brother with the pupil of one eye slanted more like that of a goat than a round one and reduced sight it that eye. He spent a week in hospital and had stitches in his eye as a kid. He was doing no more than most of our sort of age/generation did - he had a penknife and was carving his name on a tree. It wasn't the knife that got him but a bit of bark that came from the tree...

I'd guess accidents like that are rare but it would be foolish to suggest they can not happen.

Jon