Yes high blood sugar can cause immediate impaired vision but there are many other causes for blurry vision as well.
Your better off going to see an ophthalmologist
They could get to the bottom of things @el_Jimbobbio
I had blurry vision when my blood sugar was 397 after a glucose tolerance test, but it went away when my body cleared the sugar. You should definitely see your doctor. If your sugar levels are continuously high it can cause a lot of issues.