Hi Helen,
Don't worry. This totally rings a bell with what happened to me, and many others. What you're describing almost certainly isn't nerve damage to the eye: it's the temporary (and completely reversible) effect you get when the lens in your eye changes shape (temporarily) in response to the fluid it's in having a much higher sugar content. This happens when you have high blood sugar.
If this continued for a long, long time, damage in your eyes probably would result, but you can prevent that happening by getting your blood sugar down.
I'll tell you what I did. I was so horrified by the diabetes diagnosis (I was originally dX Type 2, but they found I was actually late-onset Type 1) that I just stopped eating high-carb foods. So bread, pasta, potatoes, fruit, anything starchy, and sweet things, of course. It was easy, because I regarded them as poison. I ate normal protein (eggs, chicken, meat, fish), but massively increased the green veg and salad to fill up. My BG dropped from 16 mmol to 6 within three weeks. It took my eyes about two and a half months to settle down completely. First my vision got better and better (less and less short-sighted), then it got better than it had ever been, then in the end it settled down about where it had been before. For a month I didn't need any glasses! (That was wonderful.) So, first of all, don't worry, this almost certainly isn't permanent.
But, second, don't stand for that Type 2s don't need to meter rubbish. Your eyes won't normalise till your BG is a lot lower, and you won't do it fast if you don't change what you eat. Metformin is a great drug, but it can't work miracles alone. Take ownership of your health and get yourself the
Codefree meter from Amazon. It and the strips are the cheapest, and it's fine. If you want to get well again, you cannot really do that unless you can test out the meals you eat and learn what raises your blood sugar and therefore what to avoid.
It is awful, yes, that Type 2s don't get the support of their doctors to meter. But you can do it yourself anyway, and it'll be the best thing you ever did for yourself.
You'll get a lot of help
here in Jenny Ruhl's page,
here with her nutritional calculator, and
here at Diet Doctor, a good all-round site for how to eat low carb.
Good luck.