What is the iris of the eye for?

You see through the pupil so why do we have an Iris?

What is the iris of the eye for?
The iris controls the size of the pupil, which is a hole in the iris. Changing the size of the pupil changes the amount of light that enters your eye. On a bright day, your pupils will be small, and when it is dim, your pupils will be large, to let in more light.





Pupil size also signals emotion. If you are attracted to someone, when you look at him/her your irises expand to make your pupils larger. This is an involuntary action; you cannot control it consciously. But the object of your affection can pick up on this signal, consciously or subconsciously, when he/she looks into your eyes.
Reply:The iris controls the amount of light entering the eye and hitting the retina. It closes in bright light and opens in dim light.
Reply:The iris is a muscle. It contricts or dilates to allow the appropriate amount of light, depending on ambient conditions.





When you are in the dark, your iris dilates to allow in a lot of light. Hence if you are exposed to a bright light source, you feel blinded by all of the incoming radiation. It takes a few seconds to adjust. Similarly, when you are in the light for a while, you are temporarily blind if the ambient surroundings go completely dark. it takes a few seconds for the iris to get accustomed to the new situation.
Reply:color
Reply:for looks. sexy muscle, huh?
Reply:The iris is a sphincter that dilates and constricts the pupil.
Reply:As many here have said the iris is regulating the size of your pupil. When your eyes are dark-adapted, your pupil is very big, so that much light can pass into your eye, whereas in bright light, the iris will close the pupil thus reducing the amount of light that enters the eye. The real question, however, is, why we such an aperture in the first place? To answer this question, it is necessary to take a look at the properties of lenses.





A convex lens has a certain spherical aberration. Due to the curvature of the lens, light that enters the lens at the edge will be stronger refrected than light entering the lens at the center. As a a result, the image produced has a certain imperfection (light rays from the edge are focused into a different point than light from the center, which can be reduced by through the use of an apperture like the iris. This apperture balances the amount of light available against a sharp image. So, when much light is available, the apperture can be closed further, thereby reducing the effect of the spherical aberration, while in the dark more light is allowed to enter at the expense of the sharpness of the image. To be sure, there are other aspects, as others here have pointed out (for example, regulating the amount of UV light that enters the eye etc.). But the main reason we have these beautiful irises is so that we can get the most efficient use of light to produce as perfect an image as possible.





Hope this helps.
Reply:The iris controls the size of the pupil through which light enters the eye. In a brightly lit environment, the iris will close more and results in a smaller pupil while in a dimly lit environment, the iris will open more to allow more light to enter.
Reply:Iris of the eye: regulates the amount of light that enter the eyes