Medicine from asthma inhalers can also change pupil size. Other causes are excess pressure in one
eye due to glaucoma, migraine, seizure, brain tumor or
abscess, aneurysm, horner’s syndrome, meningitis, bleeding inside the skull by head injury. If you have any of these causes or if there is blurred vision, double vision, photosensitivity, fever and headache, stiff neck or severe eye pain, go to the emergency immediately. Hope this helps answer some of your doubts. Take care.