My main aim is to get a current prescription for new glasses (that I can then get cheaply through Zenni), as my eyes have been shifting vs. my glasses, and it's gotten to the point of being a near daily irritation. I'm currently in bifocals, and when I was checking out the prices at various chain stores, those were coming in way more than I was wanting to spend ... which is why I'm going into the eye doctor (with a referral from my internist) rather than the usual option. This will also make it easier to have the prescription written out both for the progressive lenses and for individual far and near glasses (I use one for at the computer and one for movies).
However, there's also the diabetes angle ... one of the weirdest things about diabetes is how much it effects your vision. When I first came down with this (and I took forever to get into the doctor about it - my blood sugar numbers were just shy of "coma"), the main notable change was that my eyesight had completely shifted. I've been near sighted all my life, but suddenly I could see far just fine, but was needing reading glasses. As we got the sugars under control, my eyes returned to their normal (read without glasses, can't see squat at 20 yards). The process of dealing with the diabetes has been in fits and starts, and I found that I could tell in my vision differences when my sugars were high.
For most of the past year, I've been on Victoza, a nightly shot that does wonders on keeping the sugars down (I figure I'm, on average, down 100-125 points from before on just the pills), with a lot of days being in "normal person" range. My suspicion is that this shift in my sugars is also the cause of my eyes going off of my prescription. The main issue is that I'm having problems with my "near" vision lenses ... to get a crisp view of my computer monitor, I have to slide my "near" glasses way down on my nose, and when I'm out, I can't read labels, etc., unless I take off my glasses. Needless to say, I look forward to having new lenses that are right for my eyes!