If you don't have pearls you could use any type of beads, buttons or gems.
1
Gently file over, on the sunglasses, where you will place your pearls (it increases the strength between the sunglasses and the pearls).
2
File each pearl until they have one small flat edge (this is so they sit against the sunglasses easier) and glue them on.
3
Now go and wear them and watch all the compliments roll in!