Your eyes may have the little infection. When you lift something heavy, you may use a lot of strength. Your eyes may see thing in blurry state. That is normal. You should have the good rest for a while. Then the symptom of stars will disappear. Thus you do not have to worry. You need to eat more food with vitamin C in the daily life. That is very important.
The first question is whether it is a genetic situation or an exception occurring while you do heavy lifting. If you are the former, I assume that you may just suffer lack of oxygen. As we all know, when we try to stand up or squat quickly lifting a heavy object, our blood will rush out of your head in order to guarantee a rich blood supply in the arms and legs. As a result, we may feel dizzy attributed to the insufficient blood in the head. Further, a sudden rise of blood pressure has health hazards. In addition, you can try to take a deep breath before you are upright and exhale hardly when you are done. Rest a while after doing a set. So, your concentration on breathing can really help. If you are the latter, you may suffer anemia, which can be improved by balancing your diet, I mean, you need take in more food with an high iron content.
Generally speaking, anemia and abnormal blood pressure can make you feel dizzy.
In normal times, you should pay attention to getting enough sleep, and stop drinking alcohol, and stop smoking tobacco, stop eating foods that can make your blood high. At the same time, you should eat food such as dates, and peanuts.
Here is my guidance for you: go to hospital and check your blood pressure and blood when necessary.