What could cause sudden blurry spot in vision?

What causes vision to dim during hard exercise?

• What can cause vision to dim when hiking / climbing uphill? Recently I was out hiking while doing field work and had to climb up a fairly steep and tall hill. My heart was beating hard and felt strange, like something wasn't moving right inside. And then my vision started to turn dark. I continued hiking up the hill though and the symptoms continued until a few minutes after I slowed down and reached a more level spot. While I'm not an athlete, I do exercise, have normal blood pressure and normal blood sugar. But yet when I really push myself during hiking or exercising, this continues to happen. What causes this? Could it be dehydration or something related?

• Answer:

  There was not enough oxygen being processed through your bloodstream; which is why your eye-sight became dim. You need to find a better way to breathe while exercising. Take deeper breathes, to keep the oxygen flowing through your blood