An artist's depiction of a<unk>  with a bilateral arc. Many variations occur, but<unk>  usually begins as a spot of flickering light near or in the center of the visual field, which prevents vision within the<unk>  area. It typically affects both eyes, as it is not a problem specific to one eye. The affected area flickers but is not dark. It then gradually expands outward from the initial spot. Vision remains normal beyond the borders of the expanding<unk> (s), with objects melting into the<unk>  area background similarly to the physiological blind spot, which means that objects may be seen better by not looking directly at them in the early stages when the spot is in or near the center. The<unk>  area may expand to occupy one half of the visual area, or it may also be bilateral. It may occur as an isolated symptom without headache in acephalgic migraine. In teichopsia, migraine sufferers see patterns in the shape of the walls of a star fort. As the<unk>  area expands, some people perceive only a bright flickering area that obstructs normal vision, while others describe seeing various patterns. Some describe seeing one or more shimmering arcs of white or colored flashing lights. An arc of light may gradually enlarge, become more obvious, and may take the form of a definite zigzag pattern, sometimes called a fortification spectrum (i.e. teichopsia, from Greek τεῖχος, town wall), because of its resemblance to the fortifications of a castle or fort seen from above. It also can resemble the dazzle camouflage patterns used on ships in World War I. Others describe patterns within the arc as resembling herringbone or Widmanstätten patterns. The visual anomaly results from abnormal functioning of portions of the occipital cortex at the back of the brain, not in the eyes nor any component thereof, such as the retinas. This is a different disease from retinal migraine, which is monocular (only one eye). It may be difficult to read and dangerous to drive a vehicle while the<unk>  is present. Normal central vision may return several minutes before the<unk>  disappears from peripheral vision. Sufferers can keep a diary of dates on which the episodes occur to show to their physician, plus a small sketch of the anomaly, which may vary between episodes. Animated depictions File:Scintillating<unk>  - play.link=File:Scintillating zigzag<unk> .Flickering animation of a<unk> , where the scintillations were of a zigzag pattern starting in the center of vision, surrounded by a somewhat larger<unk>  area with distortion of shapes but otherwise melting into the background similarly to the physiological blind spot. File:Scintillating<unk> .A depiction of a<unk>  that was almost spiral-shaped, with distortion of shapes but otherwise melting into the background similarly to the physiological blind spot. This depiction shows the type of patterning that some have described as similar to Widmanstätten patterns. File:Scintillating<unk>  interpretation.A depiction of a<unk>  that was almost spiral-shaped, with distortion of shapes but otherwise melting into the background similarly to the physiological blind spot.
Scintillating scotoma
Persistent aura without infarction
Hutchinson's pupil
Retinal migraine
Cryptophthalmos
Macular corneal dystrophy
Persistent pupillary membrane
Nephroptosis