Ocular migraines are painless, temporary visual disturbances that can affect one or both eyes. Though they can be frightening, ocular migraines typically are harmless and self-resolve without medication within 20 to 30 minutes.
Ocular Migraine Symptoms

People with ocular migraines can have a variety of visual symptoms.

You might see a small, enlarging blind spot (scotoma) in your central vision with bright, flashing or flickering lights (scintillations), or wavy or zig-zag lines surrounding the blind spot. The blind spot usually enlarges and may move across your field of vision.

This entire migraine phenomenon may end in only a few minutes, but usually lasts up to 30 minutes.

About 60 percent of migraine sufferers also experience a "prodrome" that occurs days or weeks before the migraine attack. Symptoms of a migraine prodrome can be subtle and may include changes in mood, cravings for certain foods, or a general feeling of being tired.

Painless ocular migraines can appear suddenly, creating the sensation of looking through a cracked window. The accompanying visual distortion spreads across the field of vision and usually disappears within 30 minutes.