Ocular headaches, more commonly known as ophthalmic migraines, are related to a dilation or constriction in the vessels of the brain in or near the visual cortex (where vision is perceived). The symptoms are typically strobing or arcuate lights that flash in the peripheral vision, a horseshoe-shaped glittery or shimmering, jagged light that starts in the center and slowly expands until it dissipates completely. Some people notice that they are unable to focus on anything in the center of their vision, as if looking through a bright glare. These visual phenomena are present with your eyes open and closed, because it's not actually happening in your eyes, it's in the brain. These episodes are almost always benign, lasting for 5-25 minutes on average, and can be associated with or without a headache (although more commonly followed by an actual migraine). Though no positive causing factors are known, ophthalmic migraines are usually associated with stress and hormone fluctuation.