I am 45, female, and live on Norco for constant pain in upper back and neck (which was fused at C5-6 in Sept. of 2010). In Sept. of 2011, I had a nasty slamming back and forth whiplash motion to the neck and sometime thereafter, I noticed that anything I do where neck being bent is concerned for any amount of time (like filling out paperwork somewhere or lounging against pillow and headboard while watching a movie) will result in extreme blurred vision for several HOURS thereafter. Nothing else brings this on and my vision is otherwise fine and recently adjusted to the right correction with my newer lenses and glasses which are not bi focal if that matters. What could be the cause of this? My regular eye doctor said there was no way it was caused by the whiplash and the people at the place where I actually got my prescription for the glasses done (a different eye doctor place) said "of course it caused it!" It hasn't gotten neither worse nor betters since.
Well it's a simple logic, really - if your vision is getting blurry every time your neck gets bent, there's a connection. The eye doctor maybe hasn't taken into account that before whiplash you also had C5-6 fusion which definitely affects the force your head and eyes are exposed to. If the blurriness is so extreme that it lasts for hours, I'd recommend you to try seeing a neurologist about it, or even better, a doctor who is familiar with your spinal surgery history. Norco might be contributing to the eye blurriness, but it wouldn't cause the situation you described, the blurriness happening only in situations when your neck movement is involved,
Wish you all the best,