Visual aura is a temporary disturbance in vision arising from a brief change in the brain’s electrical activity. This phenomenon, which can occur before or during a headache or sometimes alone, involves transient neurological symptoms originating in the visual cortex. Understanding what a visual aura looks like often involves appreciating its distinct phases and the specific types of visual disturbances it can cause.
The Classic Scintillating Pattern
The most commonly described visual aura is the scintillating scotoma, often referred to as a fortification spectrum due to its unique appearance. This phenomenon is characterized by a shimmering, jagged pattern that forms the positive part of the visual disturbance.
The pattern typically begins with bright, angled lines that resemble the battlements or walls of a medieval castle when viewed from above, a shape that gave rise to the term teichopsia. These geometric shapes usually appear as sharp, zigzagging lines, forming angles or a distinct C-shape, which is the most recognizable presentation. The lines are often described as having a glittering or flickering quality, which is the “scintillating” aspect of the name.
While the pattern is frequently reported as uncolored—often silvery, white, or highly contrasting black and white—it may sometimes present with bright colors, giving it a kaleidoscopic effect. The key feature is the highly organized, structured nature of the shapes, which distinguishes it from simple flashes or spots of light.
How the Aura Develops and Fades
A visual aura is a dynamic event that follows a predictable temporal course, reflecting the wave of abnormal electrical activity known as cortical spreading depression. The aura typically begins as a small, shimmering spot or a flickering patch of light located slightly off-center from the main point of focus.
From this small origin, the visual pattern begins its slow and steady expansion, a process often described as a “march” across the visual field. The shimmering zigzag lines gradually grow outward, usually forming an expanding arc or crescent shape, which may enlarge to occupy a significant portion of one side of the visual field. This spread is characteristically gradual, typically taking at least five minutes to fully progress.
As the bright, active border expands, it leaves behind an area of reduced or absent vision known as a scotoma. The entire visual phenomenon generally lasts between 5 and 60 minutes, with the majority of episodes resolving within 30 minutes. The aura concludes when the shimmering arc reaches the outer limits of peripheral vision, where it breaks up and disappears, resulting in a full return to normal sight.
Other Visual Symptoms
A visual aura can manifest as several other distinct, non-geometric symptoms, which may occur alone or combined with the scintillating scotoma. One common manifestation is a simple blind spot, or scotoma, which is an area of partial or total vision loss not bordered by shimmering lines. This area is perceived as a dark or gray patch where visual information is missing.
Another set of positive symptoms are photopsias, which are brief, unformed flashes or sparks of light. These can appear as bright dots, stars, or simple streaks that are not organized into the complex zigzag structure.
Temporary changes in the perception of objects, known as metamorphopsia, can also occur during a visual aura. These distortions include:
- Straight lines appearing wavy, or surfaces looking as if they are viewed through heat waves or water.
- Objects temporarily looking smaller (micropsia) or disproportionately larger (macropsia).
- Temporary alterations in the intensity of color perception.
- Seeing simple, unformed colored spots in the field of view.