What Causes Vision Loss And Flash Of Light In The Field Of Vision?

About an hour ago, I sat down to my office desk and attempted to read my emails and noticed I had slight loss of vision...much like one would have after a camera light flash occurs. I tried to determin which eye it was in and it appeared to be both eyes. No other symptoms, I feel fine. Except for that freaked me out. I decided to go eat something after it occurred so I grabbed a handful of mixed lettuce greens from the fridge. About 15 minutes later the issue completely resolved. Prior to sitting down at my desk I had been doing dishes, took my daily vitamins and drank some coffee. Any ideas of what that was? thank you.