Description And Causes Of Miosis (pinpoint Pupils)

The pupils may reflect a nerve damage, or even help make a poisoning diagnosis. In today’s article, we explain why miosis or pinpoint pupils occur. We are also examining the warning signs of a possible disease state.

Miosis is the medical term for pinpoint pupils. In other words  , it’s about the contraction of the pupil – it may seem irrelevant, but it can actually say a lot about a person’s health.

This part of the eye responds physiologically to changes in light by either contracting or expanding. In addition, their size may change when a person ingests toxins or if there is a brain injury. So read on and learn everything you did not know you wanted to know about miosis.

Miosis (pinpoint pupils)

As we just mentioned, miosis consists of contraction of the pupil – the darkest part of the eye that sits in the middle of your iris. It regulates the amount of light that enters the eyeball in the direction of the retina.

It expands or contracts to regulate the light, depending on how much of it is in a given situation. It expands in dark environments – this is called mydriasis. On the other hand, pupils become smaller when there is a lot of light. It is a normal, physiological reflex that is controlled by the parasympathetic nervous system.

These movements are due to the ciliary muscle, which is the iris dilator in the eye. The sympathetic nervous system coordinates the movements.

The pupil responds to light by becoming larger or smaller.

Causes of pinpoint pupils

As explained above, miosis is a physiological process that occurs in response to the amount of light. But it is not the only situation that can trigger this reaction. Certain drugs or diseases can also trigger it, and that is what we will now describe.

Intake of opioids

Opiates alter the central nervous system. People use them either as medicine for a given disease or for recreational purposes. Fentanyl, morphine, heroin and methadone are just some of them.

They suppress the nervous system so that the pupils contract and largely do not respond to light. According to an article from the  Universidad Libre Seccional Barranquilla , the influence of opioids is characterized by, among other things, miosis as well as inhibition of breathing and consciousness.

Influence of chemicals

In addition to opioids, there are many other chemicals that can lead to miosis. In fact, it is on the list of side effects of many types of medication – for example, antipsychotics such as haloperidol. The same goes for medicines to treat glaucoma.

Horner’s syndrome and miosis

The symptoms of this disorder occur after a nerve injury. It causes pinpoint pupils and a drooping eyelid. In addition  , it increases sweat production on the affected side of the face.

According to an article in the  Acta Médica del Centro , iatrogenesis is one of the main causes of this syndrome. That is, it occurs as a result of medical malpractice following facial surgery or dental or therapeutic interventions for trigeminal neuralgia.

Cerebral hemorrhage

In some cases, this can lead to miosis, depending on which part of the brain is affected by the bleeding. This may be the case, for example, in severe strokes or if the thalamus is involved.

Pancoast tumor

This type of cancer affects the lungs, and can affect parts of the sympathetic nervous system, which is responsible for creating mydriasis, which is the opposite of miosis. Thus , the pupil cannot expand and remains contracted.

Diagnosis of pinpoint pupils

To find out the cause of miosis, the simplest way is to look at a patient’s general state of health. Many of the etiologies that produce the symptom, such as opioid exposure or cerebral hemorrhage, usually also cause a change in consciousness.

Preferably, ask the person if they are under the influence of drugs or medications if they are conscious. Also look at how the pupils respond to light. A doctor or nurse can test different eye reflexes to check the neurological condition.

The photomotor effect is one of them, and it consists in observing whether the pupil contracts more when exposed to light. Another is the consensual reflex, which looks at whether the pupil of the other eye (that which is not illuminated) also contracts. This shows whether the damage is in one of the peripheral nerves or in the upper brain.

Stroke, some tumors and certain drugs can lead to persistent miosis.

Miosis – a physiological reflex

Miosis or pinpoint pupils are a physiological mechanism that occurs in response to light. But it can also be the result of a neurological injury or exposure to certain drugs.

Therefore, it is a crucial part of a medical examination and provides a lot of information about a patient’s condition. An underlying disease must be suspected if the symptom is long-lasting.