Anisocoria results from lesions in the eye or head, migraines, and tumors. In addition, many medical conditions, injuries, or side effects of medications are also among the causes of anisocoria. Physiological or pathological causes of anisocoria can include:

Severe migraine headaches
Post-surgical side effects
Eye drops or certain medications
Horner's syndrome resulting from a disorder of the nervous system
Nerve palsy
Eye or head trauma
Glaucoma
Inflammation inside the eye
Brain aneurysms
Concussions and trauma
Brain tumors
Certain types of cancer

Evaluation is necessary to determine the underlying cause of anisocoria. Treatment, therefore, varies depending on the underlying condition and is planned on a case-by-case basis.