Visual loss

Visual symptoms

Frances Wilkinson (2004) argues that the visual aura has a potential value as a window on brain function, and she quotes W.R. Gowers who stressed - already in 1895 - the importance of ascertaining trustworthy facts about the aura:

"The difficulty of ascertaining the facts depends on their subjectivity. That which is to be discerned can only be seen through the vision of another. Moreover, this is the sight of the unreal; it is the sight of that which is not. Yet, though unreal to the subject it is, as a sensation, a profound reality which confuses the mind and may make even recollection painful. Hence the opportunities for ascertaining trustworthy facts a very rare, and when they come it is important that they should be made the most of." (Gowers, 1895)

Positive Symptoms

There are many different forms of positive symptoms.

• Visual hallucinations (e.g., flickering lights, spots or lines)
• Visual illusions
• Visual loss (positive scotoma)

The best-known visual migraine aura is the so-called fortification spectrum, a scintillating zigzag figure of bright luminous geometrical lines and shapes. (Note that a negative scotoma, i.e., a negative symptom, may be an integral part of the fortification spectrum.)

Fortification spectrum, reproduced from a computer model from Dahlem and Müller (2003) and Dahlem et al. (2000)

Negative Symptoms

Negative visual symptoms are visual field defects (negative scotoma with loss of vision) that travel through the visual field. The scotoma gradually expands into a sickle- or C-shape in the homonymous visual hemifields. At the advancing (convex) edge of the scotoma may appear zig-zag patterns.

References

Dahlem MA, Engelmann R, Löwel S, Müller SC. Does the migraine aura reflect cortical organization? Eur J Neurosci 2000; 12: 767-770.
Dahlem MA, Muller SC. Migraine aura dynamics after reverse retinotopic mapping of weak excitation waves in the primary visual cortex. Biol Cybern 2003; 88: 419-424. [PDF]
Gowers WR. Subjective visual sensations. Trans Ophthalmol Soc UK 1895; 15: 1-38.
Wilkinson F. Auras and other hallucinations: windows on the visual brain. Prog Brain Res 2004; 144: 305-320.

Author: Klaus Podoll
Last modification of this page: Sat. Dec, 11. 2004

Visual loss

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