What is the Function of the Pupil of the Eye?
World is a very beautiful place to live. This world consists of blue sky, colorful flowers, twinkling stars at night, green meadows and so on. We won’t be able to enjoy this beautiful world without our eyes. Eyes are one of the five sense organs in our body. If we look at the anatomy of the eyes, it has iris, pupil, retina etc. to make the vision possible. Here, we will discuss the pupil of the eye and its functions. If you have observed the eyes, you can see that the size of the pupil increases or decreases depending on our emotions as well. Let us learn the function of the pupil in our eye and when they will dilate.
Pupil Eye- Definition
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The definition of the pupil eye is a small black opening in circular shape located at the centre of the iris. Iris of the eye is the coloured annular ring having the pupil at the centre. The iris consists of connective tissues and muscles attached to the pupil. The colour of the pupil is black in colour for everyone. But the colour of the iris can be different for different people, ranging from light blue to dark brown. The colour of the eye depends upon the amount and quality of melanin present in the front layers of the iris.
Pupil of the Eye - Function
If we look at the anatomy of the pupil of the eye, it is a circular hole present at the centre of the Iris. The light reflected from an object passes through the pupil of the eyes and reaches the retina and an image of the object is created in our brain. The function of the eye is to regulate the amount of light passing through the pupil of the eye. The pupil by itself cannot control the amount of light passing through the pupil and reaching the retina of the eye. The iris helps to change the size of the pupil and thereby controls the amount of light passing through the pupil. There are two tiny muscles in the iris that help to change the size of the pupil. They are circular muscles and radial muscles. The radial muscles connect the pupil to the iris and circular muscles are located around the iris. The contraction and the relaxation of these muscles decides the size of the pupil to increase or decrease.
It is important to regulate the amount of light passing through the pupil. It is because if a large amount of light passes through the pupil and reaches the retina, it will damage the retina as in case of sunlight reaching the retina directly. If less light is passed through the pupil and reaches the retina, the vision will be difficult. Therefore, the pupil ensures that almost a steady amount of light is passing through the pupil.
How Pupil of the Eye regulate the amount of light?
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Let us see how the size of the pupil is changed to regulate the amount of light.There are muscles and connective tissue between the iris and the pupil. When bright light falls on the pupil, the circular muscles in the iris contract and the radial muscles relax which reduces the size of the pupil. Therefore, the amount of light passing through the pupil for a bright light is reduced and an image is formed on the retina comfortably. This is what happens when we go outside on a brighter sunny day, we will feel uncomfortable at first due to bright light reaching our eyes. Then the size of the pupil decreases and the amount of light passing through the pupil is also reduced. Then we can easily see clearly without any discomfort due to bright light. So, in bright conditions, we have a dilated pupil eye.
On the other hand, when it is dark and not clearly visible, the circular muscles relax and the radial muscles contact. This causes the pupil to dilate and the amount of light passing through the purple increases.This helps to maximise the vision of our eyes. A good example to understand this is when we go inside suddenly to a dark room. We will not be able to see clearly because of the low amount of light reaching our eyes. But as the time progresses, the pupil gets dilated and the amount of light passing through the pupil increases. Thereby increasing our vision at dim conditions.
Our emotions can also affect the size of the pupil.The pupil tends to dilate if we are delighted or surprised and the pupil size becomes small when we are angry. If we are in a fight or flight situation, the pupil dilates. In a situation of fight or flight, it is crucial that the vision of our eyes has to be very clear. To ensure that we are able to see properly, the pupil is dilated along with other sympathetic actions. The pupil of a dead person will always be dilated. To check whether a person is dead or alive, we can check the pupil of the person and if it is not constricting, then we can confirm that the person is dead.
Conclusion
The smaller circular opening of the iris is called pupil of the eye. The function of the pupil of the eye is to control the amount of light passing through the pupil. It is the responsibility of the iris to control the size of the pupil using circular and radial muscles. The contraction and relaxation of these muscles control the size of the pupil. The pupil constricts in bright conditions and the pupil of the eye dilates in dim conditions. The dilation and constriction of the pupil is also triggered by our emotions. The pupil dilates when we are surprised or pleased and the pupil constricts when the person is angry or doubtful. A dead person will have a dilated pupil eye.
FAQs on Pupil Eye
1.What is the role of iris in the dilation and constriction of the pupil?
Ans: The amount of light passing through the pupil and reaching the retina of the eyes depends on the size of the pupil. The size of the pupil is controlled by the contraction and relaxation of circular and radial muscles in the iris. In bright conditions, the circular muscles contract and radial muscles contract and the pupil constricts. Hence, the size of the pupil is reduced and the amount of light passing through the pupil also decreases. In dim conditions, the circular muscles relax and radial muscles contract so that the pupil dilates. Therefore, the amount of light passing through the pupil also increases making the vision in dim conditions possible.
2.Why do people in photographs sometimes have red eye pupils?
Ans: When light falls on an object, we see the object in that colour that is reflected by the object. Thus, a red ball reflects red colour so we see the colour of the ball red. If most of the light is absorbed, then the colour of the object is black. The colour of the pupil eye is black because when the light passes through the pupil and reaches the retina, most of the light reaching the retina is absorbed.
While using a camera, we turn on the flash in dim conditions. In dim conditions , the pupil is dilated so that the amount of light passing through the pupil increases. But when the camera captures the picture by flashing the bright light just for a moment, there is not enough time for the pupil to constrict. This allows a large amount of flash light to pass through the pupil and reach the retina. The retina contains many blood vessels and when this bright flash light falls on the blood vessel on the retina, the red colour of the blood is reflected and the pupil of the person in the photographs looks red in colour.
