My son is 16 yrs old , he is 5 11 and 140lb, and nearsighted,he is usually experienc blurry vision, dizziness when he standing up, and sometimes chest pain ( it doesn t occurs when he standing), we checked with his family Dr, he said it is most likely dehydration. But today I wake him up at 6am and he felt bad chest pain it stays for more than half an hour and went away, and now he has soccer practice he experiencing the most widest blurry vision and dizziness he was like lost couldn t understand what is going on the coach stop him from practicing. Just to let you know today is really hot day ( heat wave).