So even in a bright room, the eyes stay dilated. These drugs affect the muscle that widens the pupil, slowing how it reacts to light. Anti- seizure drugs, such as phenobarbital ( Luminal) and topiramate ( Topamax)ĭilated pupils are one sign that someone has used illegal drugs, such as:.Tricyclic antidepressants like amitriptyline ( Elavil) and desipramine ( Norpramin).Parkinson's medications such as amantadine ( Symmetrel) and carbidopa-levodopa ( Sinemet).Motion sickness and anti- nausea medicines such as dimenhydrinate ( Dramamine) or a scopolamine patch.Decongestants, like pseudoephedrine ( Afrinol, Sudafed).Antihistamines, like diphenhydramine ( Benadryl, Genahist, Naramin, Sominex, Unisom).Atropine ( Atropen), which treats problems with heart rhythm, stomach issues, and some types of poisoning.Medicines, injuries, and diseases can all cause this eye condition.Ī few medicines can affect the muscles that control your pupils and prevent them from getting smaller when light shines in. Sometimes your pupils can dilate without any change in the light.

When it’s bright, they get smaller, or constrict, to let in less light. In low light, your pupils open up, or dilate, to let in more light. Your pupils get bigger or smaller, depending on the amount of light around you. Muscles in the colored part of your eye, called the iris, control your pupil size. What's going on? Those dark circles are your pupils, the openings that let light enter your eye so you can see. You look in the mirror and notice that the dark circles in the middle of your eyes are bigger than usual.

One fixed dilated pupil