Honestly, my nuero-opth. believes I have always had it, but that I have never noticed it because it never really caused a problem. Now that I have Chiari I am paying more attention to every little "quirck" my body has, so I'm noticing it more. Also, this is one of those things that gradually gets worse with age. So it may have been unnoticable before, but as I get older the nystagmus will get more and more apparent.
There are a lot of things that could cause this condition, but here's one way to tell, when your eyes drift or bounce do they go up and down or left and right? If they go up and down then it is directly related to Chiari, if they go side to side it is not chiari related. if you can't tell for sure wich way the movement is going your doc. will be able to. I originally saw an opthimologist (not an optomotrist, they are different) who saw the nystagmus and recommended a neuro-opthamologist just to be sure this wasn't chiari related. So a regular opthomologist may be able to help you, it's just that mine had very minimal experience with chiari and he wanted to play it safe.
Good luck to you, and remember - find a specific doc. for each of your specific symptoms, one neurologist, no matter how competent or intelligent, can't know everything! If you have a sore tooth you go to a dentist not a neurologist right? So if you have eye problems, ear problems, stomach problems, joint problems, sleep problems, mood problems, etc, find the right doc.!!
I have the nystagmus too. If yours was not caused by the Chiari, then what is it from? No one understands me when I talk about it. Its like I can see things but they are cloudy or out of focus and glasses don't help. It takes awhile for my eyes to adjust on an object. Everyone sees it as just being near sighted or far sighted but it is so much more than that and it drives me crazy. Is there anything that can be done for this?
For your eye problems, I reccommend seeing a neuro-opthamologist. I saw one because I was experiencing nystagmus, which is rapid movement of the eyes, and my neuro-opth. was able to tell me very quickly and easily that it wasn't even related to my Chiari. Remeber your neurologists and nueorosurgeons can't know everything, they are human just like we are, find docs who specifically specialize in the exact area you are having trouble in.
I had surgery in Feb and having another one done in Aug. My doctor told me that chiari symtoms can be there even after surgery. Stress can play a big factor. Also my research shows that the surgery isn't a cure it's just for relief of symtoms. It wouldn't hurt you to get a second opinion.
I had decompression surgery 4 months ago and I am still having some complications. I still have a headache and the pains in my legs as well. A friend of mine's younger brother was diagnosed and this and had surgery last summer. He has curvature of the spine as well. I know that if left untreated the chiari can cause this, but since you had it treated, the doctor should look into why this is happening now. Good luck!