Why do the men beach volleyball players wear lens-less glasses?

Question

I'm watching the men's volleyball in the Olympics right now and the US players are wearing lens-less glasses......

Answer 1

Either the lenses fell out, or the men were sweating/it was raining and they were messing with their vision so they took the lenses out. But they still had to wear the frames because they were sponsored to do so.

Answer 2

They could be for eye safety.

Answer 3

They are doing that to maintain sponsorships with Oakley.  When at night, they don't need them, so they take the lenses out.  You have to keep those who give you money happy!

Answer 4

IM WATCHING IT 2!!!! and its because some company is paying them money to advirtise there sunglasses. but theres no sun in the stadium so they took the lenses out