If you have seen this "doctor" before and different optic nerve sizes is new then that is a source of concern and you should see a neuroophthalmologist. Find one near you at www.aao.org
On the other hand if this is a "new" doctor then its possible that he/she is wrong or that there has been a size difference all your life. This is especially true if one eye is farsighted which causes small optic nerves and the other is myopic which causes larger optic nerves.
Yes it is weird to ask you to come back in a month. Maybe see a ophthalmologist for a second opinion.
I went to the eye dr. yesterday as well (one I had never seen before) and she told me that my right optic nerve was bigger than my left.
My vision in my right eye has always been worse than my left.
I also have Meniere's Disease (uni-laterally, and it happens to be on the right side). I had gentamician injections to treat that, which comes along with a huge list of side effects. It made me wonder whether any of these things were related.
I asked the dr. what that meant and she didn't give me a straight answer.
I have searched the literature in the database at the university I attend, but can't find anything to my question.
Anyone have an ideas/hypotheses/answers?