What causes your pupils to dilute?

Question

In your eyes what causes them to go bigger?

Answer 1

Muscles in the eye either relax or contract to adjust the dilation of the pupils... the purpose of them dilating is to let in more light, so you can see more clearly. They'd be more dilated when you're in dim light than when you're in bright light

Hope this helps!

Answer 2

Drugs

Answer 3

all kinds of things:  

sympathetic nervous response

pharmaceuticals

defocusing (relaxing accommodation

darkness

extra innervation to the pupil dilator musculature

Answer 4

The pupil is the opening that allows light to enter the eye. It’s the black part of the eye. When the eye needs to allow more light to enter the eye the pupil dilates or grows in size. When too much light is entering the eye the pupil constricts or shrinks in size.

changes due to the lighting are not the only reason that your pupils will change in size. Drugs like benzodiazepines and CNS analgesics such as morphine cause the pupil to constrict more than normal. Other drugs such as marijuana, hallucinogens, cocaine, and amphetamines cause the pupils to dilate more than usual. Sexual arousal, excitement and fear will also cause your pupils to dilate more than usual.

There are short term changes in your pupil size that tell more specific information about what’s going on in your head. If you think about something that you enjoy or interests you, your pupils will momentarily grow. Think about something that you don’t like and they will momentarily shrink.

The ability to dilate your pupils can really come in handy in social situation. There have been lots of studies on the subject and it has shown that people will unconsciously find you more attractive and friendlier with dilated pupils. (This is why romantic restaurant are dimly lit.) So the next time you’re with someone that you want to build rapport with, think about something that you really like and dilate those pupils.

Hope this helps... this is mostly copyed from a site.