Impression of scintillating scotoma occurring in an artist
Scintillating scotoma is the most common visual aura preceding migraine. This depiction is showing the distorted field alone; it does not depict the normal parts of the field of vision.
A scotoma is any area of alteration in the field of vision. Some are due to defects in the eye or the optic nerves, but scintillating scotomas are not. They are caused by migraines (or many other possible causes) interfering with the processing abilities of the occipital cortex. The scintillating scotoma flickers and blurs vision, but is never dark. It can hinder ability to read and drive, among other things.
Clinical Lectures on Diseases of the Eye. J. Elliot Colburn, 1902.