Under scotoma (from ancient Greek σκότος skótos "darkness") is understood in ophthalmology a part of the visual field , the sensitivity - mostly pathological - is reduced. In the case of complete loss of sensitivity ( blindness ) for this sub-area, one speaks of an absolute , and in the case of only partial loss of sensitivity of a relative scotoma.
Scotomas can occur due to a disease of the retina , the visual pathway, or the visual center . For example, a vascular occlusion in a blood vessel supplying the optic nerve can lead to an irreparable scotoma due to the failure of nerve fiber bundles . Temporary scotomas such as ciliated scotoma z. B. in the context of a migraine can occur suddenly; they usually completely regress within a relatively short time.
A central scotoma or fixation point scotoma without an organic cause usually occurs on the cross-eyed eye with eccentric fixation as long as the other, centrally fixing eye is open. This prevents double vision ( diplopia or confusion ) that would otherwise occur . As soon as the leading eye is closed, this functional scotoma of the cross-eyed eye can no longer be detected.
A physiological (not pathological) absolute scotoma represents z. B. the blind spot caused by the entry of the optic nerve into the eye. A typical arcuate visual field loss in glaucoma that emanates from there is called Bjerrum's scotoma .
Affected people describe a perception of bright, flickering or kaleidoscopic rotating light in a mostly eccentric part of the field of vision, which initially expands, but does not cover the entire field of vision. The occurrence happens suddenly. At first, the person affected may have the feeling of having looked into a strong light source, because experiencing a flickering scotoma can be similar to glare. As with glare, it may no longer be possible to fix objects or text directly. If only part of the field of vision is affected by the failure, orientation in space is entirely possible.
A ciliated scotoma can be accompanied by nausea, vomiting and headache, especially if it occurs as part of a migraine ( migraine aura ), but it often occurs without these side effects. The simultaneous occurrence of high sensitivity to light and other hypersensitivities also occurs.
The occurrence of a shimmering scotoma is limited in time. It usually takes about 20 to 30 minutes.
If a flickering scotoma sets in while driving, you should drive to the side of the road as quickly as possible and wait for the scotoma to end.
The cause of the ciliated scotoma is unknown. Because of the very similar perceptions of many migraineurs, one suspects a similar mechanism of origin as in migraine. However, shimmering scotomas without migraines usually only occur for a few months. Ciliated scotomas without migraines usually do not require treatment.