Alice in Wonderland syndrome (AIWS), or micropsia, is a disorienting neurological condition which affects perception by the human eye.
Sufferers perceive objects (including animals and other humans, or parts of humans, animals, or objects) as appearing substantially smaller than in reality. Generally, the object appears far away at the same time. For example, a family pet, such as a dog, may appear the size of a mouse, or a normal car may look shrunk to scale. This leads to another name for the condition, namely, Lilliput sight. The condition is in terms of perception only; the mechanics of the eye are not affected, only the brain's interpretation of information passed from the eyes.
The syndrome is associated with, and perhaps in part caused by, the classical migraine headache. Occasionally, Alice in Wonderland syndrome is named as one of the first symptoms of mononucleosis. There is some suggestion, unsubstantiated, that certain ingredients of cough syrup may help cause micropsia. Small children, usually between the ages of five and ten, form a large proportion of those afflicted. It is sometimes a temporary condition, especially for children. Micropsia occurs especially during darkness.
Micropsia does not only affect visual perception, but also one's hearing, sense of touch, and sometimes one's own body image; the syndrome continues even when the eyes are closed. Peripheral symptoms include anxiety, apraxia, and agnosia.
The disorder is named after Lewis Carroll's Alice's Adventures in Wonderland, where the title character experiences many situations similar to those of micropsia and macropsia. Since it is known that Carroll suffered from migraines, there is some speculation that he might have written that work from direct experience.