The Great Gatsby: Dr. T. J. Eckleburg

Seriously though, who is Doctor T. J. Eckleburg? His name reoccurs numerous times throughout Fitzgerald's The Great Gatsby and I don't have a clue as to the significance.  He seems to be associated with New York City i think because his name is mentioned when the group travel there.  I am guessing that the name or the fact that he's a doctor, or something along those lines, is some symbol that plays a part in the novel.  I haven't a guess of what the symbol stands for or why it is necessary though, which is a little aggravating.  I really don't think the doctor is a real person though.   The book never mentions any action or detail regarding anything human about the "doctor" and though I have tried to catch any symbolism in this book, I feel like I am letting the vast majority slip right through my fingers.  I actually discussed this book with my mom who read it all the way back in her high school years, probably at least twenty or twenty five years ago, and she remembers a lot of symbolism being present in the book. One particular piece that she recalled was the green light, I assume the one outside the Buchanan house, and its meaning for Gatsby as his life take on the meaning of getting closer to that green light, to Daisy and hope and happiness. I am actually excited to see what other symbolism  might have gone right over my head when we discuss the novel in class.