Marianna,
I had a similar experience. Unfortunately, I didn't have a pre-op image of my eyes to compare, but when I saw the ophthalmologist post-op, she felt that both my optic nerves were swollen. She talked to Dr. Schwartz at House who did my surgery to ask if this was to be expected, and he said no. I had a very nerve-wracking day in the ER, where she sent me for additional CT scans, MRI's, and MRA's (image of the vascular structure in my head). Fortunately, the neurologist at the hospital didn't think I needed the lumbar puncture the ophthalmologist asked for! (I had already spent five days with a lumbar drain in the hospital.)
All the tests checked out ok. She then referred me to a neuro-ophthalmologist who looked at all the scans and took more pictures of my optic nerves, and after an additional follow-up appointment concluded that my optic nerves were not swollen - that was just normal for me.
I did do some of my own research (googled "papilledema" (swollen optic nerve) and "acoustic neuroma") and found several studies reporting that 8% of acoustic neuroma patients will report with papilledema. In fact, one cause of papilledema is a brain tumor. Duh - I already knew I had that! Although my tumor is gone now, my theory is that the swollen appearance of my optic nerves is a residual effect. As far as I can tell, it hasn't had any impact on my vision one way or another (hard to tell with all the ointment in my eye!)
Although I don't know if your "change" has the appearance of being swollen, it is interesting to hear from another ANer with a potential effect on the optic nerve. I'll be curious to hear how yours turns out.
Pam