It always a good idea to use shooting glasses if you have defective vision, even if it's so slight your optician would not normally advise correcting it.
Slight astigmatism is a defect not normally corrected, especially if you have no other vision defect, but it is important to correct for shooting.
Even if you have the correct shooting lens there is no guarantee you will not still have the same problem. A blurred sight picture can be the result of many things other than defective vision;- lighting, tiredness, problems with the extended sightline just to 3!
IF IT'S NOT BROKE.........DON'T FIX IT!