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Eyes
Biology
Human Anatomy and Physiology

Why does the pupil size change?

Answer

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December 18, 2011 5:42PM

It depends on how much light your eyes receive, in dark places or when you close your eyes your pupils dilate (mydriasis) to increase the ammount of light they can take in, conversely, when looking at an intense light the pupils contract (miosis) to decrease the ammount of light. This is called the photomotor reflex and involves the sympathic (mydriasis) and parasympathic (miosis) nervous pathways.