What is mydriasis?

Mydriasis is generally defined as dilation of the pupil. In the Blog ofClínica Bavierait is defined as the increase in size of the muscle fibers that make up the iris.

It is commonly a natural reaction of our eye, even as we mentioned previously, it is considered a reflex. It is more common than we think, since we do not perceive this dilation movement.

Causes of mydriasis

Apart from being a natural movement, there are other causes and in addition to this they can be considered as symptoms of diseases, both visual and of another nature. The main reasons will be mentioned below.

Dim ambient light

Ambient light is the most recurrent factor to cause the dilation of our pupils. When there is little light the pupils tend to expand, thus increasing the amount of light that our eyeball will receive.

For this same reason, our pupils are dilated just at the moment of waking up and throughout the adaptation process.


Mood swings, especially when they occur suddenly, usually produce this reaction in the body, especially when these emotions are exciting and prone to enthusiasm.

It should be noted that the influence of emotional effects on pupil dilation will not be influenced by the amount of light that is in the place. It becomes oblivious to these conditions and focuses on showing, in some way, the way we are feeling about something.

Chemical agents and psychoactive substances

The ingestion of chemical agents and psychoactivesubstances cause dilating effects on the pupils. This is mainly due to the excitation of the fibers, since they have a direct effect, but also due to the reaction that our organism has when facing these conditions.

There are substances that also produce the opposite effect and a clear example of this is Marijuana ( Cannabis sativa ).

Neurological diseases

Neurological diseases are closely linked to the Central Nervous System , so they can be manifested through mydriasis.

In this sense, the presence of tumors or symptoms of possible anomalies that are developing are the reason for an alteration that we must take into account and monitor responsibly.

In addition to this, it is essential to mention that a hemorrhage would produce this effect by modifying the regular size of our pupils for a long period of time, even varying the sizes in each eye.

Brain damage

We have seen on many occasions, in movies or television series, that one of the first tests carried out on people with traumas is the correct functionality of the pupils. For what is this? To its contraction and expansion in the face of light stimuli.

A correct functionality of these reflexes will be decisive to rule out the possibility of brain damage. The inability to react or a perennially dilated pupil will be warning symptoms.

eye injuries

Diseases such as glaucoma or a structural condition in our eyeball, will be sufficient reasons to produce mydriasis, which will indicate the failure in the correct functionality of our organ.

Abstinence syndrome

According to the Institute of Neurosciences of Guayaquil, among the main symptomsof withdrawal syndrome is mydriasis, described as pupil dilation.

Types of mydriasis

Mydriasis is classified mainly due to its nature and way of acting and affecting. Next we will mention what they are.


Physiological is the natural response of our vision. It is an increase between normal values and is not considered as any alteration, but as a reflection of our visual field.

Benign unilateral

It is of the isolated type, since it affects presenting an evident pupillary asymmetry. In some cases, it occurs as a pathological consequence and is for reasons such as clinical symptomsafter anesthesia of a patient undergoing surgery or interventions of any kind.


It is the contraction of the dilator muscles of the iris, where the minimum stimulation of one, produces the reaction of both. This can be a consequent reason thanks to a trauma or the consumption of certain chemical substances.


This type of mydriasis, then known as areactive mydriasis, is characterized by presenting a dilation of the pupils, increasing their size considerably, but there is no regression to normality or contraction even in the presence of the correct stimuli.

Treatment for mydriasis

When mydriasis becomes an anomaly problem, beyond being a natural response of our eyeballs, certain treatments are considered to control and improve these reactions. We present them below.

Avoid exposing yourself to the sun

Faced with extreme dilation, unnecessary exposure should be avoided due to increased sensitivity in the eyes when they are ready for this type of response, since it does not have the adequate capacity to adapt correctly to the ambient light, presenting inconveniences. with the dilator muscle.

Wear dark glasses

The use of dark glasses mitigates the difficulties described above and protects against photophobia that is usually triggered by the presence of the extreme dilations described.

Consult a specialist

Understanding then, that although it may be an anomaly that comes without bad omens, prevention is always much better than regret.

Consult a specialist about the presence of unusual features and always maintain correct control over our vision, allowing us to detect pathologies and anomalies in our body in general and apply surgeries on time, if necessary.

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