What is mydriasis, what are its causes and is treatment necessary?


Mydriasis is the dilation of the pupil under the influence of irritants. The process is ensured by relaxation of the optic sphincter - the circular muscle responsible for narrowing the pupil. Physiological mydriasis occurs reflexively, for example, when the lighting becomes worse, or if a person looks into the distance. Mydriasis is characteristic of states of stress and fear (remember the proverb “Fear has big eyes”?), as well as surprise, joy, and euphoria.

The main difference between physiological mydriasis and other varieties is that the dilation of the pupil is always temporary. As soon as the stimulus disappears (the lighting becomes brighter, the person calms down), the pupil diameter again approaches normal - 2-4 mm. Another symptom of pathological mydriasis is uneven pupil dilation.

What causes mydriasis

Pupil dilation is called pathological mydriasis if there are no natural pathogens to trigger the reaction. This condition can be caused by external or internal factors. Depending on the cause of the pathology, mydriasis is divided into:

Name of pathology Description
TraumaticThis mydriasis occurs when there is an injury to the eye, such as a contusion. In this case, the pupil dilates to 7-10 mm and does not react to light. Eye surgery may also be a cause.
ParalyticThe pupil dilates due to paralysis of the sphincter of the pupil. Mydriasis occurs when the nucleus or root of the oculomotor nerve is damaged, pathologies of the central nervous system, or an acute attack of glaucoma. Paralytic mydriasis is also observed in cases of poisoning with cocaine, quinine, and carbon dioxide.
SpasticCaused by spasm of the pupillary dilator, the muscle responsible for pupil dilation. The cause may be irritation of the cervical sympathetic trunk, damage to the brain or spinal cord. Spastic mydriasis is also observed in certain pathologies of the heart, gastrointestinal tract, lungs, and thyroid gland.
MedicationThe cause of drug-induced mydriasis is the effect of the drug. Products containing atropine, scopolamine, tropicamide and other substances are used. Such drops are instilled by ophthalmologists to examine the visual apparatus or before surgery.

Mydriasis and miosis (pathological reduction in pupil size) can be symptoms of dangerous diseases such as meningitis, multiple sclerosis, encephalitis, brain tumor, diabetes mellitus. This is why you cannot ignore the condition when the pupils are of different sizes: the sooner you see a doctor, the higher the chances of stopping the disease in the early stages.

A person with pupillary mydriasis complains of a cloudy image, a feeling of a film on the eye, and difficulty focusing. Depending on the causes of the pathology, the symptoms may be supplemented:

  • nausea and vomiting;
  • headache;
  • lethargy, fatigue;
  • lacrimation;
  • pain in the eyes;
  • sensation of a foreign body in the eye, etc.


Physiological dilation of the pupil occurs in low light and when looking into the distance. When a person experiences severe stress, under the influence of the sympathetic nervous system, mydriasis occurs, the eyes (pupils) dilate - the saying “fear has big eyes” is about this. This reaction is normal and its purpose is to improve vision.

Physiological mydriasis is always temporary, it lasts as long as the action of the stimulus lasts, and when the conditions change (fear passes, the light turns on), the pupils return to normal.

Physiological pupil dilation is caused by the following factors:

  • lack of lighting;
  • emotional arousal (both positive and negative);
  • great surprise; increased attention to something;
  • looking into the distance;
  • reaction to surprise, for example, a sharp loud sound;
  • deep breath.

Mydriasis can be medicinal or drug-induced. In this case, he is called specifically so that the ophthalmologist can conduct an examination of the fundus or perform surgical intervention. Dilation of the pupils is achieved by instillation (dropping) into the eye of a drug that causes temporary paralysis of the sphincter of the pupil - the circular muscle that constricts the pupil. Such drugs include Midriacil, Irifrin, Tropicamide. Atropine has a similar effect, but is used less frequently, since its effect lasts much longer, up to two weeks, which can lead to significant inconvenience for the patient. Sometimes drug mydriasis can be a side effect of therapy, for example, when treating a spasm of accommodation.

There are many causes of pathological mydriasis, including:

  • intoxication with chemicals, carbon monoxide;
  • overdose (intoxication) with certain medications (Atropine, Scopolamine, Platiphylline, Ephedrine);
  • drug use (hallucinogens, cocaine, ecstasy, methamphytamines, cannabis);
  • diseases of the central nervous system (brain tumors, dislocation syndrome, stroke);
  • fractures of the base of the skull or orbit;
  • spinal cord injuries;
  • eyeball injury;
  • acute oxygen deficiency;
  • aneurysm of the posterior communicating artery;
  • near-death state, coma;
  • preeclampsia (complication of pregnancy);
  • congenital pathologies (hydrocephalus);
  • ophthalmological diseases (glaucoma, myopia, iridoplegia, inflammation of the optic nerve, iridocyclitis, Bumke syndrome, Pourfure du Petit syndrome, blindness of various etiologies, paralysis of the ciliary muscle);
  • infectious diseases (tuberculosis, neurosyphilis, botulism, diphtheria, viral infections);
  • pathologies of the nervous system (Adi syndrome, epilepsy, Parkinson's disease, sympathicotonia, encephalopathy, migraine, cranial nerve neuropathies);
  • systemic diseases (multiple sclerosis);
  • diseases of internal organs (kidney and liver failure, heart and lung diseases, some pathologies of the digestive system);
  • metabolic disorders (thyroid pathologies, diabetes mellitus).

Diagnosis of eye mydriasis

The first thing the ophthalmologist is convinced of is that pupil dilation is not physiological. Further examinations include:

  • checking the visual organs using an ophthalmoscope;
  • CT or MRI of the brain;
  • neurosonography;
  • Ultrasound of cerebral vessels;
  • lumbar puncture;
  • general blood and urine analysis, etc.

If the problem is not only ophthalmological, but also neurological, the patient must be sent to see a neurologist.


Mydriasis itself does not require special diagnostic methods, as it is detected visually. However, a thorough examination is necessary to identify its cause, without which treatment is impossible.

Primary diagnosis consists of collecting anamnesis, identifying associated symptoms, events preceding mydriasis, as well as an ophthalmological examination with mandatory ophthalmoscopy.

The patient is prescribed laboratory tests:

  • clinical (general) blood test;
  • clinical urine analysis;
  • blood chemistry;
  • blood test for hormones, primarily thyroid hormones.

Instrumental diagnostics include:

  • CT (computed tomography) and/or MRI (magnetic resonance imaging) of the head;
  • Ultrasound (ultrasound examination) of the abdominal organs;
  • ECG (electrocardiography);
  • chest x-ray.

Further diagnosis depends on what is found from the examination results. Depending on the nature of the identified pathology, consultation with related specialists may be necessary: ​​neurologist, neurosurgeon, endocrinologist, traumatologist, etc.

Treatment of mydriasis

Unilateral or bilateral mydriasis caused by medication goes away within 24 hours. If the pupil does not constrict, miotic drugs are prescribed.

In other cases, treatment is aimed at eliminating the underlying disease. For example, in case of an acute attack of glaucoma, medications are prescribed that narrow intraocular pressure and normalize blood circulation, as well as drops that narrow the pupil. If these remedies do not help, surgery is prescribed. To eliminate mydriasis in cases of damage to the nucleus of the oculomotor nerve caused by an aneurysm, an operation is performed to remove the aneurysmal sac pressing on the trunk of the nerve. For cerebral edema, drugs are used to remove excess fluid.

The prognosis for pathological mydriasis in most cases depends on how timely treatment is started. For example, the sooner the factors affecting the nerves are eliminated, the faster and more effectively they will recover.


The main sign of mydriasis is the dilation of the pupil to 7-10 mm (normally its diameter is from 2 to 5 mm). If subsequent contraction of the pupil does not occur, this condition is accompanied by visual and general symptoms.

Visual symptoms:

  • increased photosensitivity, intolerance to bright light;
  • lack of reaction to light;
  • lack of reaction to an object approaching the eye;
  • decreased visual acuity;
  • burning, pain in the eye (or both eyes, if mydriasis is bilateral);
  • rapid eye fatigue;
  • lacrimation;
  • disturbance of eye movement in one or more planes;
  • discomfort, pain when reading, watching TV, working at the computer.

With prolonged mydriasis, the following may appear:

  • deformation of the pupil, it takes on a pear-shaped, teardrop-shaped or sharply oval shape (slightly oval pupils may be normal);
  • ptosis (drooping eyelid);
  • strabismus.

Deformation of the pupil in mydriasis

General symptoms accompanying pathological dilation of the pupils:

  • headache;
  • dizziness;
  • sleep disorders;
  • emotional instability, anxiety.

Mydriasis, caused by a certain disease, is accompanied by symptoms characteristic of this disease.

In children, pathology manifests itself in the same way as in adults.


To prevent mydriasis, it is recommended:

  1. Refusal of drinking alcohol, psychoactive substances, smoking.
  2. Use of any medications as prescribed by a doctor in compliance with the prescribed dosage.
  3. Avoiding eye injuries (protection with special glasses at work, etc.) and head.
  4. Early detection and treatment of diseases that can lead to pathological dilation of the pupils.
  5. Undertaking preventive examinations with an ophthalmologist, if there are unpleasant symptoms associated with the eyes, immediately contact a specialist.

Diagnosis and treatment

Diagnostics includes examination, patient interview, and MRI. The doctor collects the necessary tests and, if necessary, gives a referral to a neurologist. Treatment will directly depend on the underlying pathology. It can be medicinal and surgical. For quick elimination, eye drops are used. With the medicinal type of the disease, mydriasis goes away on its own without therapy. In the traumatic form, the dilated pupil may persist for several weeks. But in general the prognosis is always positive. It is not recommended to use the drugs yourself. Before doing this, you need to consult a specialist so that he can prescribe the dosage.

Traumatic mydriasis

It is not difficult to determine the traumatic form of mydriasis in humans. As a rule, dilated pupils appear in most people as a result of external physical influence on the body. For example, mydriasis may appear due to physical injury to the eyes or after undergoing surgery on the organs of vision.

If a person received a strong blow to the head, which led to concussion, then in this case mydriasis is a temporary phenomenon that will gradually go away on its own. With traumatic mydriasis, the pupil remains wide due to paralysis or so-called sphincter paresis. In addition, it should be noted that if a person’s pupils are constantly dilated, this may indicate the appearance of various lesions in the brain (tumors, ischemic processes).

Main causes of mydriasis

  • eye injuries (mostly blunt, non-penetrating, which do not lead to serious impairment, but cause eye contusion);
  • damage and compression of the oculomotor nerves;
  • traumatic brain injury with damage to nerve endings;
  • neoplasms in the head;
  • hypoxia;
  • barbiturate poisoning;
  • infectious diseases that affect intracranial and ocular nerve nodes.

Sometimes mydriasis is one of the symptoms of diabetes.

Dilated pupils can be induced artificially using eye drops. Ophthalmologists resort to this when examining the organs of vision, as well as before performing a number of eye surgeries. In other cases, it is necessary to establish the causes and stop the symptom itself.


Physiological and drug-induced mydriasis do not require treatment; in this case, the dilation of the pupils goes away on its own after the action of the etiological factor ceases.

Pathological mydriasis is not an independent disease, but a symptom of some pathology, therefore etiotropic treatment consists of measures aimed at the underlying disease.

Drug therapy

To eliminate mydriasis, in some cases, the use of drugs that weaken the effect of the dilator and stimulate the pupillary sphincter may be indicated. For this purpose, drugs of the following groups can be prescribed:

  • alpha-blockers (Tropafen, Prazosin, Phentolamine);
  • M-cholinomimetics (Pilocarpine, Aceclidine);
  • N-cholinomimetics (Cititon, Lobelin).

Pilocarpine is a drug that in some cases is used to eliminate mydriasis

Depending on the underlying disease, the following may also be prescribed:

  • diuretics;
  • nootropic drugs;
  • antiplatelet agents; and etc.

General recommendations

In case of pathological dilation of the pupils, the following restrictions must be observed:

  1. Avoid too bright lighting, exposure to open sun;
  2. Wear dark glasses outside;
  3. Refuse to drive a car during treatment, read long texts, or work at the computer.
  4. Stop smoking, drinking alcohol and taking psychoactive substances.
  5. Avoid self-medication and drug abuse. Take any medications only as prescribed by a doctor, strictly following the prescribed dosage.


Surgical treatment is indicated in cases where the causative disease requires it, mainly:

  • brain tumors or cysts;
  • hematomas or abscesses of the brain;
  • aneurysm of the posterior communicating artery.
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