Your blood sugar levels influence your sight to a great degree. If you exercise hard without a bit of food you may lower your blood sugar. It may also be because you aren't getting enough iron. Iron apparently helps the form of Haemoglobin which carries oxygen in your blood. If not enough oxygen is getting to your eyes then you may experience problems.
There is nothing wrong with your eyes. The blurred vision after exercise usually caused by insufficient supply of oxygen or some insufficiency of optical nerve. When you stop exercising and have a rest for a while, the blurred vision will go away by itself. So don't worry.