I used to suffer blurred vision when my blood sugar levels were yo-yoing up and down all day. I only get it now because of if I have something naughty which for me is not recommended.
If your blood glucose levels are not controlled, this is one of the symptoms.
Stabilising your blood sugar levels is the best way to treat it. My vision went from long sighted to short sighted, then after getting good control, the vision changed back.
Don't be buying glasses, if it's recommended by an optician. Wait until you know what happened to you. If you need glasses go to poundland and buy the cheap ones.
Why did you refuse the sitagliptin?
I suspect you have read that it can cause bad side effects. But you looted for metformin and Glicizide, which is more likely to cause problems with your control and other health issues.
Ask your GP if he has given you the glicizide because of insulin resistance. Because you don't have enough insulin to control the spike that is happening, mostly from the carbs you are still eating. Sitagliptin does this for me.
Have you tried a low carb diet as this will help with control.
Keep safe