Explanation of pupil

If humans had the same brain to eye ratio,our eyes would be the size of grapefruits.The tarsier's enlarged orbs haven't evolved to make it cuter, however,but to gather as much light as possible.Bigger eyes can have larger openings,called pupils,and larger lenses,allowing for more light to be focused on the receptors.While tarsiers scan the nocturnal scene with their enormous peepers, cats use gleaming eyes to do the same.