The size of the pupils depends on the balance of sympathetic and parasympathetic activity supplying the iris:
The pathway of the pupillary light reflex consists of:
It should be noted that the lateral geniculate nucleus of the thalamus and the cerebral cortex are not involved in the pupillary reflexes. Hence a patient who is cortically blind will have intact light reflexes.
Annotations allow you to add information to this page that would be handy to have on hand during a consultation. E.g. a website or number. This information will always show when you visit this page.