Mydriasis is a rare eye condition that is the subject of many medical studies. Read and find out all about the causes, symptoms, diagnosis and treatment of this unique disease.

Mydriasis Definition

It is a condition that is characterized by prolonged dilation of the pupil of the eye. In people affected with this disorder, the pupil remains dilated for an abnormally long duration. It fails to come back to a normal state even after a long period.

Picture 1 – Mydriasis

The condition is sometimes referred to as “Blown Pupil” by medical providers.

Mydriasis Types

This condition is classified into two types:

Unilateral Mydriasis

It is a type of fixed mydriasis which is believed to be a sign of stroke or some forms of brain dysfunction.

Bi-lateral Mydriasis

It is a rare eye disease. Not much is known about this subtype.

Traumatic Mydriasis

It is a type of Mydriasis caused by blunt trauma to the orbit of the eye. A blunt injury can lead to small ruptures in the iris sphincter muscle, thereby resulting in pupil dilation. The pupil fails to react normally to light and remains bigger than its counterpart in the other eye. Although it continues to briskly react to light, it will not have as much constriction as an unaffected eye. The vision may be slightly impaired.

Mydriasis Symptoms

As aforementioned, this condition is characterized by dilation of pupils for a long time. Affected individuals typically do not experience any painful symptoms. However, discomfort prevails until the condition is fully treated.

Some affected individuals fear other problems, such as headaches, as symptoms of this condition. However, such problems are actually found to be coexistent difficulties that are likely to be present only as a coincidence.

In any healthy person, the pupils of the eye get larger or smaller. The extending of the pupil is formally known as dilation. Its narrowing in size is referred to as constriction. If the dilation and constriction fails to occur in a normal way, people are likely to suffer from abnormal dilation. This can lead to large pupils. The condition is known as Mydriasis and can occur due to various factors.

Mydriasis Causes

The condition can result from a number of causes. These include:


In some cases, the condition is found to arise due to an extremely strong sexual arousal. The excitement associated to arousal leads to the natural release of a hormone called Oxytocin. The release of this substance can lead to mild Mydriasis. Sexual affection results in minor dilation while intense sexual arousal leads to highly enlarged pupils. In a particular case, orgasm along with an ocular precondition has been found to cause Pupillary block.

Autonomic neuropathy

Autonomic neuropathy refers to a cluster of symptoms that arise when the nerves that manage daily bodily functions suffer damage. The oculomotor nerve that caters to the extrinsic muscles of the eye is involved with parasympathetic nervous supply. It is the parasympathetic nervous supply that leads to the constriction of the pupil (Miosis). Damage to the oculomotor nerve is typically exhibited as mydriasis.

Multiple central nervous system disorders

Disorders affecting the central nervous system, such as impending brain herniation, stroke and epilepsy, and are known to lead to temporal mydriasis as well. A severe brain condition, such as a rapidly enlarging brain tumor, can lead to an oculomotor nerve compression.


Trauma to the head or the eye is also regarded as one of the most common causes of this condition. An injury of the head or the eye can cause damage to the iris sphincter, the muscle that closes the pupil. Injuries can also cause damage to the nerves controlling the iris sphincter. Traumatic mydriasis can eliminate or reduce reactivity to light.


Use of certain medicines may also give rise to this condition. Anticholinergic medications, such as scopolamine, hyoscyamine and atropine block the muscarinic acetylcholine receptors present in the eye. Due to this, the pupils are incapable of constriction. Naturally, dilation occurs. Dilation also arises due to use of most hallucinogenic drugs, such as mescaline, psilocybin and LSD along with some other tryptamines and phenethylamines. These medicines affect the serotonergic 5-HT2A receptors located in the brain and causes Mydriasis as a natural consequence. Serotonin boosting drugs can cause the condition in a way similar to 5-HT2A-mediated psychedelics.


Mydriatics are drugs that cause dilation of the pupil. Medications, such as Tropicamide, allow examination of the retina as well as other deep ocular structures. They also decrease painful spasms in the ciliary muscle.

Miosis and Mydriasis

Mydriasis is often contrasted with Miosis, a condition that occurs when the pupil of the eyes get smaller. However, Miosis typically results from a natural response of the sphincter muscle of the Iris (in the form of a reflex contraction) to certain drugs or bright light. However, Mydriasis is a reflex pupillary dilation that arises in response to a reduction in light. It also occurs due to certain drugs.

Mydriasis Diagnosis

Picture 2 – Mydriasis Image

Once dilation of pupil is detected, it is important to seek immediate medical attention. Patients of this condition should consult professional health specialists. Medical care providers typically suggest a few tests that help them analyze the symptoms and find out the actual cause of the problem. Once properly detected, the condition can be treated and eradicated completely.

Mydriasis Differential Diagnosis

The differential diagnosis of Mydriasis, which is more severe in bright light, aims at distinguishing it from other conditions like:

  • Third nerve palsy
  • Adie tonic pupil
  • Cranial nerve dysfunction
  • CN III dysfunction
  • Pharmacologic blockade
  • Pharmacologic mydriasis
  • Traumatic mydriasis

Mydriasis Treatment

The condition is usually treated with the aid of drugs and eye-protection devices. In acute cases, a surgery may be conducted. If the condition is strong enough to require a surgical intervention, Phenylephrine drugs such as Cyclomydril is used. The most common medications that are used to cure this condition include:

  • Phenylephrine
  • Scopolamine
  • Murocol-2

Doctors usually recommend use of eye protection gears until the condition is completely treated. During treatment phase, patients should use light-sensitive sun glasses or contact lenses that are opaque-colored. This prevents any adverse reaction to the affected eye.

Mydriasis Complications

The condition does not really cause serious problems to the eyes. Complications, if any, arise from the actual underlying cause and not Mydriasis itself. There are no major complications or risks associated to this disorder.

Mydriasis Prognosis

The condition has a positive outcome which actually depends on the management of the disease and its timely treatment. If cured in time, the condition can be only temporary. However, the problems may persist permanently if treatment is ignored for a long time or carried out improperly. The outcome of Mydriasis that arises due to health conditions primarily depends on the treatment of that condition itself.

If any of your friends or family members is showing pupil dilation, seek immediate medical treatment. If treated in time, Mydriasis may only be temporary and patients are likely to make a faster recovery.

One Response

  1. Faiz Alam November 10, 2017

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