<unk>  is a subtype of<unk> , a visual disturbance defined as the persistence or recurrence of a visual image after the stimulus has been removed.<unk>  is a broad term describing a heterogeneous group of symptoms, which is divided into hallucinatory<unk>  and<unk> .<unk>  is likely due to sustained awareness of a stimulus and is similar to a visual illusion: the distorted perception of a real external stimulus.<unk>  is caused by migraines, hallucinogen persisting perception disorder (HPPD), prescription drugs, and head trauma, but is also sometimes idiopathic.<unk>  consists of afterimages that are short-lived or unformed, occur at the same location in the visual field as the original stimulus, and are often exposed or exacerbated based on environmental parameters such as stimulus intensity, background contrast, fixation, and movement.<unk>  symptoms occur continuously or predictably, based on environmental conditions. The term is from Greek: palin for "again" and opsia for "seeing".
Illusory palinopsia
Oscillopsia
Facial weakness
Meralgia paraesthetica
Hallucinatory palinopsia
Hemifacial spasm
Akinetopsia
Photopsia