It is not normal for you to see stars in front of your eyes when you do exercises. Your eyes may get infection because of the invisible bacterium. You need to use some eye drops with anti-inflammation to get rid of your bacterium and make your eyes get bright and clear. You could also use some warm compress to make your eyes get comfortable and bright.
No, it isn't. You may have eye floaters. You pay more attention to observe your condition, if you stare something bright (white paper, blue sky), small moving spots in your eyes will much noticeable than ever. So you cannot get complete scene. Also there is possible that your iris is hurt or you get corneal inflammation. Then you may feel dizzy and pain, even your vision will be affected when doing exercise.
Well, knowing the causes helps you to take care of yourself. A low blood sugar, dehydration and improper breathing usually lead to the dizzy sensation, especially when you work out before eating breakfast or missing meals. Orthostatic hypotension can occur then. As we all know, our body use sugar as a fuel source to assist our normal activities. Also, the low blood sugar affects people in various ways, commonly like dizziness, weakness, blue mood of vulnerable individuals, or even arrhythmia. What is more, although it can be relieved easily, it may cause shock without timely rescue. In addition, drinking plenty of fluids or eating fruit can add energy and make you feel better soon. It is wise to eat a snack before exercise next time.