It may be the cause but equally it may not. Higher levels can cause fatigue, certainly. The problem with your eye needs to be seen by a health care professional, blurry vision can be caused by higher levels and conversely can be caused when at first we see those high levels falling, however, if at all possible, I would suggest you see an optician or your nurse sooner rather than later. You will be given (if you havn't already) an appointment for Retinopathy Screening, make sure you mention it to the Diabetes Specialist Nurse.
Good luck and I hope you begin to feel better soon.