Shanam.......As a former flight attendant for a major airline for 20 years....I have known many blind people. They were always boarded first, but only because they would have been run over by all of the inconsiderate people that wanted to get to their seats first. They were usually accompanied by a Passenger Agent, and sometimes with a guide dog. They were always given the utmost respect from the Airline crew. I really don't remember whether or not they had dark glasses on. It breaks my heart to think that anyone would ever make fun of anyone's disability! As far as your question, about whether or not I would assume someone wasn't blind because they were not wearing dark glasses.........no, I try never to assume anything. Shanam, since your disability gives you the pleasure of having a guide dog, you are able to go through daily life with the help of your best friend, Loretta. I'm so proud of your ability to meet this challenge with an open mind, kindness, and even laughter! You are a wonderful person, and I'm so honored to be your friend. 
joyce