to moderate mydriasis. Long term effects of drugs can also cause mydriasis, for example opioid withdrawal. Autonomic neuropathy Parasympathetic fibers travel with cranial nerve III, the oculomotor nerve, to innervate the circular layer of muscle of the eye (sphincter pupillae). Damage to this nerve typically manifests itself as mydriasis, because the sympathetic supply to the pupil, which causes mydriasis, remains unaffected, and therefore unopposed. Multiple central nervous system disorders e.g. epilepsy, stroke, and impending brain herniation are known to lead to temporal mydriasis as well. A brain catastrophe, or a rapidly increasing brain mass, can cause compression of the oculomotor nerve. Trauma In cases of head injury or orbit trauma (eye injury), the iris sphincter (the muscle responsible for closing the pupil) or the nerves controlling it can be damaged, reducing or eliminating the normal pupillary light reflex. References External links Category:Medical signs Category:Ophthalmology