It may be due to low blood sugar or low blood pressure. You may want to check with a Doctor just to be on the safe side.
Is it normal if my vision goes blurry every time I exercise, and takes around 10 minutes to go back to normal if I'm extremely nearsighted?
If you have a pre-existing eye condition that could very well answer your question, but you want see the doctor to rule out any other medical condition such as related to Blood pressure, Heart, Blood sugars