What do the glasses hide?

Hello community, my song may sound a little trivial but I'm worried because Bruno Mars usually comes out in his videos with sunglasses man will be that he prefers us not to see what he really hides behind his eyes? or give you a status to use them because as we know today accessories for singers are as indispensable as his voice, if someone wants to give me your opinion you can do it or if you know something that I do not know about this singer, greetings and peace.