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.
Then the green man fitted spectacles for the Scarecrow and the Tin Woodman and the Lion, and even on little Toto; and all were locked fast with the key.
Then the Guardian of the Gates put on his own glasses and told them he was ready to show them to the Palace.

Taking a big golden key from a peg on the wall, he opened another gate, and they all followed him through the portal into the streets of the Emerald City..