I'm diabetic.sudden blurry vision ( e.g. i can't read road signs while driving). should i need a fondus oculi or tomography? thanks

Poor sugar control: A common cause of blurred vision in diabetics is poor blood sugar control which alters the lens focusing ability. I am guessing that in between episodes the vision is restored. If that is true, then diabetic retinopathy, a feared complication of this condition, probably is not present. In any case, see your ophthalmologist for a check and your family doc for better sugar control.