What Causes Visual Halo In Right Eye Accompanied With Sinus Congestion?

About a week ago, I experienced a halo around my right eye in the extreme perriferral vision field. It lasted about 5 minutes while shopping in a grocery store. It disappeared. Never had migraines (ever). I had been having sinus congestion & pressure in my forehead & behind my eyes on & off for a week or so before. I am 35. No medications regularly. Do not wear glasses or contacts.