If it was the Chanel sunglasses, then you should have sent them using Simple Delivery - that was the service shown on your listing.
As long as you sent them by this method, using the label supplied by Ebay, then the buyer needs to open a case stating that the sunglasses were damaged in transit.
Then, Ebay should refund the buyer without requiring them to return the glasses and you, the seller will not need to do anything.
"There are two ways to be fooled. One is to believe what isn't true; the other is to refuse to believe what is true.”
Søren Kierkegaard, Danish philosopher (1813 - 1855)
