The pupil size is controlled by the sympathetic and parasympathetic branches of the autonomic systems.

The pupil light response is controlled mainly by the parasympathetic system. It constricts the pupil in response to light and reduce this constriction in dark. Damage in this pathway reduce the pupil constrictions, so problems in the light response goes together with larger and not smaller pupils. It is called Adie tonic pupil, or Holmes syndrome and it is common in Sjogren Syndrome.
Parasympathetic damage can also cause reduced tearing and dry eyes, or it can affect the accommodation reflex which cause pupils constriction when focusing on a near object.

Damage to the sympathetic pathway can cause Horner Syndrome - small pupils, falling of the upper eyelid, and reduced sweating around the eye.
It can also cause a slower pupils dilation in dark.