I have been training 6 months regularly, cycling and running mostly and swimming once a week. I used to train in 2009 from 2000. I am 27 years old, and my situation is that I see like transperant spots that just the out line is visible and a dot inside same color as the out line of the spot. This happen after mostly for the duration of the exercise, not sure till long it last because I just get used to it. I am sure its not a matter of rest because I make sure to rest for recovery.