micropsias

Micropsia is a perceptual disturbance in which objects are experienced as smaller than their actual size. It is a type of metamorphopsia, a broader class of visual distortions that can affect size, shape, or distance. When described in the plural form micropsias, the term may refer to multiple episodes of this distortion occurring over time, or to the phenomenon as it appears in different individuals.

Clinically, micropsia can affect one or both eyes and may involve objects, faces, or scenes appearing deceptively small. It is commonly transient and linked to other conditions such as migraines with aura, especially in the context of the Alice in Wonderland syndrome. It can also occur during temporal or occipital lobe seizures, after head injury, or in association with structural brain lesions. Patients may report accompanying symptoms such as distortions of shape, altered depth perception, or homonymous visual field changes.

Causes and mechanisms are diverse but generally involve abnormal processing of visual information in the brain, rather than primary retinal disease. The most frequent associations are neurologic or neuropsychiatric, including migraine disorders and epilepsy, but micropsias can arise from tumors, vascular events, or post-traumatic changes affecting the occipital and temporo-parietal visual pathways. The precise mechanism is thought to involve cortical misregistration and altered receptive-field processing in higher visual areas.

Diagnosis centers on clinical history and neurological examination, with imaging (MRI) or electroencephalography (EEG) as indicated to identify structural lesions or seizure activity. Management targets the underlying condition, with migraine treatment, antiseizure medications for epilepsy, or observation if episodes are transient and benign. Prognosis is typically favorable when the underlying cause is reversible; persistent symptoms warrant neurologic evaluation.

See also metamorphopsia, Alice in Wonderland syndrome, and visual aura.