The Wizard of Oz by Lynam Frank Baum Chapter 10 Page 14

must wear spectacles night and day. They are all locked on, for Oz so ordered it when the City was first built, and I have the only key that will unlock them.”

He opened the big box, and Dorothy saw that it was filled with spectacles of every size and shape.

All of them had green glasses in them. The Guardian of the Gates found a pair that would just fit Dorothy and put them over her eyes. There were two golden bands fastened to them that passed around the back of her head, where they were locked together by a little key that was at the end of a chain the Guardian of the Gates wore around his neck. When they were on, Dorothy could not take them off had she wished, but of course she did not wish to be blinded by the glare of the Emerald City, so she said nothing.