How do you unlock the door above the eyewear store on Spy island?

Answer:
Ask Dr. Spyglass for an eye exam. When he points to a symbol, choose the one that faces the opposite way (M instead of W, backward E instead of E), and he will know you are a fellow spy. When he leaves, go outside and enter the upstairs through the outside door.
First answer by ID1202138346. Last edit by Dfoofnik. Contributor trust: 2552 [recommend contributor recommended]. Question popularity: 1 [recommend question].