I Have Had This Happen To Me Twice Now, Within

I have had this happen to me twice now, within a year. My left eye goes slightly blurry and I see a washer like object but thinner like a ring. The ring itself is black. Inside the ring are alternating triangles, one up one down, slight space between each one and never touching. The triangles are alternating in color.
The first time it happened it lasted a few hours, the last time it happened, it only lasted a few minutes.
Thank's in advance for your help.