Thanks for posting in. Eyedrops can be one reason of you have been using. 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.