Then the most common cause would be "entopic phenomena" to learn more use the search feature or archives. Also go to wikipedia.com and read their article on it.
JCH MD
I did today.. and she said everything is fine.. she dilated my eyes and said everything is healthy...but im still experiencing the light little circle flash
start with a medical eye exam by an ophthalmolgoist. Find one at www.aao.org
JCH MD