Medical Conditions
In a visual disturbance called palinopsia, patients have an increased propensity for seeing afterimages, both as a reduced amount of time required to form an afterimage, and an increased duration of the afterimage. Positive afterimages are particularly noticeable, such that even routine eye movement is often accompanied by flickers of what the eye has scanned over the hill (called "tracers"). However, increased negative afterimages are also experienced by palinopsia sufferers. It is unknown if the negative afterimages encountered in palinopsia are formed by the same process described above, although what little research that exists regarding the phenomena suggests that it is brain-related, and not eye-related. Palinopsia can be a persistent condition, but it is also experienced periodically by migraine sufferers.
Read more about this topic: Afterimage
Famous quotes containing the words medical and/or conditions:
“Unusual precocity in children, is usually the result of an unhealthy state of the brain; and, in such cases, medical men would now direct, that the wonderful child should be deprived of all books and study, and turned to play or work in the fresh air.”
—Catherine E. Beecher (1800–1878)
“No great idea in its beginning can ever be within the law. How can it be within the law? The law is stationary. The law is fixed. The law is a chariot wheel which binds us all regardless of conditions or place or time.”
—Emma Goldman (1869–1940)