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The ocular structure has many parts and probably one of the best known is the pupil, but do you really know what it is?

It is the black spot that is in the center of the eye, specifically in the iris, and which has the function of regulating the amount of light entering the eyeball.

The pupil can measure between 3 and 4,5 millimeters, but its diameter can increase or decrease as contracted or dilated.

En Área Oftalmológica Avanzada Next, we explain what the pupil is and what eye diseases can affect it. 


What is the pupil of the eye?

The pupil is the black spot that is in the center of the iris and has the property of contracting or dilating to regulate the amount of light entering the eye. 

For the pupil to accommodate to the light exposureTwo muscles are necessary: ​​the circular iris muscle or iridian sphincter, which helps with contraction, and the dilator muscle, which opens the pupil.

The pupil dilates in low light or dark spaces and contracts when we are exposed to a lot of lighting. The size of the pupil varies based on the amount of light in the environment, due to certain moods, drug use or neuronal damage. 

Through dilated pupil, ophthalmologists can examine the posterior chamber of the eye and diagnose conditions associated with taint, optic nerve or to choroid

What is the function of the pupil?

The function of the pupil is to regulate the amount of light that enters eye structure. When the person is in a very dark place, the pupil dilates so that more light enters the retina and images can be formed. 

But what happens when we are at the beach? When we are exposed to a lot of bright light, the pupil contracts to filter the amount of light that can enter the eye and thus protect the eye socket.

The docile property of the pupil allows its power of accommodation.   

Pupil diseases

There are some conditions that can affect the functioning of the pupil in the eye, let's know what they are: 


La myosis It occurs when the pupil does not dilate in the dark, but remains contracted to less than 2 mm. The use of cholinergics and the application of narcotics are the main causes of myosis. 


La mydriasis It is the opposite of myosis. The pupil remains dilated to more than 6 mm and does not contract when exposed to light. The use of topical eye drops such as atropine, trauma and injuries to the motor nerve can cause mydriasis.


La anisocoria It is the unequal size between the two pupils. The difference in size may range between 0.5 mm and 1 mm. He consumption of certain medications or the presence of trauma, ischemia, a angle-closure glaucoma o migraines can cause anisocoria.  

Horner syndrome 

This condition occurs due to the interruption of a nerve pathway that runs from the brain to the face and eye on one side of the body. The syndrome causes the pupil to contract and the eyelid to droop.

Do you need more information about the pupil? Contact us in Área Oftalmológica Avanzada to solve all your questions.

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One of the best known parts of the eye is the pupil, but do you really know what it is and what is its main function? We make it clear to you!
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Área Oftalmológica Avanzada
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