Why do pupils dilate?

Our eyes are the most important sensory organ of our body. Many people are intrigued by the way in which our eyes function. You might have noticed that at the centre of our eye is a black circle which is known as a pupil. The function of this pupil is to allow the passage of light.

Once the light is passed through the pupils, the cells which are inside our eyes sense the light which helps us in developing a visual of what we are seeing. If you have noticed, pupils can change in size and this is what we would be talking about today.

The term pupil dilation means that the size of the pupil is increasing. Along with the size of the pupil the ring which is immediately next to the pupil on the outer side is known as Iris and this is made of muscles and this expands along with the pupil as well.

The Iris as well as the pupil, move in tandem that is if the size of the iris increases than the size of the pupil would also increase and if the size of the pupil decreases than the size of the Iris would also be decreasing. The size of the pupils would be changing depending on the presence of light. We would be explaining this phenomena below.

Why do pupils dilate?

As we mentioned above, the function of the pupils is to allow the passage of light to the sensing cells which are inside our eyes. When the light in our surrounding is more, the pupils contract to pass only a limited amount of light so that the cells which are on the inside are able to easily visualise what we are saying but in a darker surrounding the presence of light is already less and therefore pupils try and pass through as much light as possible and for this they expand and this procedure is known as the dilation of pupils.

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The cells which are inside the eyes take a bit of time to adjust this change and also they need minimum threshold of light to develop a picture of our surroundings and that is why, in order to pass through that amount of  light even in darker surroundings, the pupils dilate so that they can pass through more amount of light.

You can feel or sense this phenomena, when you come from outdoor to indoor because during the day, in the outdoors there is a lot of sunlight but when you might be coming indoors, you might sense that it is very dark inside and this is due to the change in the size of the pupils depending on the light which is present in the surrounding.

When there is a change in the level of light in the surrounding, pupils do not change the size instantly but they take some time due to which you think that it is too much dark in the indoors even though the lights might be on.

Testing of the dilation of your eyes:

Why do pupils dilateThere is a procedure which is known as Mydriatics and this procedure is used by the doctors to observe the phenomena of dilation in your eyes to ensure that the eyes are functioning properly. There are eyedrops which cause your pupils to dilate so that the doctor is able to examine how your eye is adjusting to the greater amount of light.

Since the pupils would be dilated for quite some period of time after you put in the drops, whenever you are putting in the drops, you would be advised to wear sunglasses so that the extra light which is being passed on to the cells inside your eyes does not affect you. The reason is that when the eye is subjected to a higher quantity of light continuously, it can damage the eyes as well and that is why a sunglass is always recommended.

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Dilation of the pupils due to drugs:

While the above drug might be knowingly administered to dilate the pupils to check the condition of the eyes but there are some of the drugs which can have a side effect of the dilation of the pupils. Shrooms are one of them. Some of the antidepressants can also cause the dilation of the pupils as well.

Pupil dilation due to poison:

picture of eyesWhenever any chemical which is acting as a poison enters your body it causes the dilation of the eyes. Whether this chemical is injected by the bite of a insect or whether it is a substance which is injected orally in your food, it would always be causing dilation of your pupils. Excessive exposure to certain chemicals also causes the dilation of your pupils and one such chemical is chloroform. Jet fuel also produces the same reaction of dilation of pupil.

Involuntary pupil dilation:

The Iris which is around the pupil is controlled directly by the nervous system and therefore whenever the nervous system is responding to something suddenly, the reaction is also the dilation of the pupils. In most of the cases, the poisons which can produce at least some kind of chemical reaction in our body result in pupil dilation.

Pupil dilation due to arousal:

When a person is aroused, due to the chemicals which are present in the bloodstream of the person that is the hormones, there is pupil dilation as well. Pupil dilation is also caused if you see a person whom you find attractive.

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As you can see, pupil dilation is not just limited to a couple of caurses but it can be caused in a variety of situations and some of them are in our control but mostly, the situations which can cause pupil dilation are not in our control and therefore you might be experiencing pupil dilation without any control of yours, you might not be able to even realize that you are going through pupil dilation unless and until you sense the extra passes of light through your eyes due to the pupil dilation.

So, now you have your answer to your question why do pupils dilate?, You would be able to figure out the cause of pupil dilation as well as the solution to bring the pupil to normal position as well. In most of the cases, pupils return to their normal size after a specific amount of time.