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If you need to dilate your pupils on command, try imagining a dark room or dark shapes, such as a camping ground at night. Alternatively, focus on an object that's far away or unfocus your eyes to make your pupils widen. You could also try drinking an espresso, since caffeine can help trigger your iris muscles to relax. If you want to shrink your pupils instead, stare directly at natural light, but not the sun, or focus intently on an object close by. For tips on what substances to avoid when trying to dilate your pupils and what prescription medications you can take to shrink your pupils, read on!