Circulation

Hi, I have  a problem with my vision when I exercise I get areas of reduced vision, a bit like when you have looked at a bright light,these areas are always in the same place, in both eyes. I have seen an opthalmologist who says there is nothing wrong with my eyes, but said perhaps it could be due to circulation, I also have had a couple of treadmill tests for blood pressure and ecg in the last few years, and also a carotid artery scan, they are all normal, my blood pressure is also fine, I do have osteoarthritis of the neck, could this be affecting my eyesight in someway by restricting the blood flow, I would be extremely grateful for your advice as this is really worrying, I have had this four about five years