DefinitionAnisocoria is unequal pupil size. The pupil is the black part in the center of the eye. It gets larger in dim light and smaller in bright light.Alternative NamesEnlargement of one pupil; Pupils of different size; Eyes/pupils different sizeConsiderationsIt is normal for a person's two pupils to be up to 1 mm (.05 inch) different in size.Babies born with different sized pupils may not have any underlying disorder. If other family members also similar pupils, then the pupil size difference is possibly genetic and nothing to worry about.Also, for unknown reasons, pupils may temporarily differ in size. If there are no other symptoms and if the pupils return to normal, then it is nothing to worry about.Unequal pupil sizes of more than 1 mm, that develop later in life and do NOT return