Bright perfect circle in vision while running?

I just got home from work and I run on the treadmill at our gym before going home each night.  Today I went from my usual 1.5-1.75 to 2 miles, I was running without any incline, and at only a pace of 6mph or a 10 minute mile.  I am a 27 year old male, and am in relatively good shape.  I have been having occasional dizzy spells that doctors have been looking into for the last 3 months, and I have only had this bright "sun spot like" circle appear one other time when I was dehydrated.  However this time I feel that I was adequately hydrated and that at this pace it shouldn't have been too much of an exertion issue, at the peak of the run my heart rate hit 170, and during the cool down walking which I started at 2 miles due to the bright glowing perfect circle in my vision (large too, not like a small sun spot from a light), my pulse stayed around 98-106.  I had no way to check my bp, so I am unsure of that.  Also I have been occasionally seeing bright flashes of light at the computer screen and once after lifting weights, I had the same bright flashes swirling in a circle I believe it was only in my left eye, I was told that was an eye migraine?  By someone or an ocular aura I believe someone else mentioned.  I am a bit concerned and would like some advice as to what it may be and the type of doctor I will be off to next...  Thanks in advance for any help.

[Ray T Oyakawa, MD]

See an ophthalmologist first.

Dr. O.

[cjgsay]

Any ideas of what it was or what happened?