March 24, 2023
dilated pupils

What are the causes of dilated pupils?

If you look in the mirror in your eyes, you will notice that the pupil of your eye is narrowing and widening. Pupil dilation is a natural reaction to too much or too little light, but there may be other factors involved that we will discuss in this article. Stay with us.

What is pupil dilation?

The pupils are black round circles in the center of the iris (the colored part of the eye) that allow light to enter the eye. The size of the pupils is constantly changing. When the pupil enlarges, it is called the pupil dilation. In low light, this is normal and causes more light to enter the eye. Narrowing or shrinking of the pupil occurs when there is a lot of light, and narrowing of the pupil causes less light to enter the eye.

The cause of dilated pupils

This complication may be due to other factors, including:

  • Dilation of the pupil of the eye due to drug use;
  • Pupil dilation due to certain diseases;
  • Pupil dilation during eye examination;
  • Pupil dilation due to injury.

Pupil dilation can occur in both eyes or in just one of them, a condition called anisocoria.

1. Dilation of the pupil of the eye due to drug or medication

The pupil may dilate due to the use of certain medications and drugs. Usually, when the effect of the drug diminishes, the pupil returns to normal. Their pupils do not respond naturally to light stimuli and do not contract when exposed to large amounts of light. Of course, it is up to the doctor to diagnose the effect of the drug by opening the pupil of the eye.

Drugs associated with pupil dilation

  • Atropine for the treatment of cardiac arrhythmias, stomach problems and various types of poisoning;
  • Types of antihistamines such as diphenhydramine;
  • Anticonvulsants such as pseudoephedrine;
  • Remedy for motor and antiemetic diseases such as diphenhydrinate;
  • Parkinson’s drugs such as amantadine;
  • Tricyclic antidepressants such as amitriptyline;
  • Botulinum toxin (Botox);
  • Antiepileptic drugs such as phenobarbital;
  • Drugs such as amphetamines, cocaine and ecstasy.

Symptoms of dilated pupils due to medication or drugs

  • Change of mental state;
  • skin dryness;
  • Fever;
  • Flushing;
  • Myoclonus (sudden, involuntary shaking, shivering, or contraction of a muscle);
  • Epilepsy;
  • Frequent urination.

Symptoms of anticholinergic poisoning

Blurred vision;
heart beat;
Shortness of breath;
Frequent urination;
Memory problem;
Visual illusions.

2. Dilation of the pupil of the eye when examining the eye

During a comprehensive eye exam, an optometrist or ophthalmologist drops drops into the eye, causing the pupil to dilate. It takes about 20 to 30 minutes for the drops to take effect, allowing the doctor to examine specific pupil reactions and conditions such as neurological problems and the internal structure of the eye, including the retina, vitreous, optic nerve, blood vessels (choroid), and macula.

It takes about a few hours for the effect of the pupil dilator to subside, so it is best to have the patient with you.

3. Dilation of the pupil of the eye due to a blow to the head

Damage to the eye or brain can also cause the pupil to dilate. Trauma may damage the iris sphincter muscle (responsible for narrowing the pupil) or one of the brain pathways that controls it. It can also cause bleeding inside the skull, which results in dilated pupils. Eye injuries can also be the result of intraocular surgery such as cataract removal and corneal transplantation or retinal surgery.

4. Diseases associated with dilated pupils

Abnormal dilation of one or both pupils can be a sign of a serious illness that affects the brain. These diseases include:

  • stroke;
  • Internal bleeding;
  • Cerebral aneurysm;
  • Brain tumor or abscess;
  • High eye pressure due to glaucoma;
  • Encephalitis;
  • Intracranial hemorrhoids;
  • Acute stroke;
  • Intracranial tumor;
  • Increased intracranial pressure;
  • Infection of the membrane around the brain (meningitis or encephalitis);
  • Migraine headache;
  • Epilepsy;
  • Tumor, mass or lymph node above the chest;
  • Horner syndrome;
  • Ocular nerve palsy caused by diabetes;
  • Head injury.

5. other things

According to new studies, high levels of the hormone oxytocin (love hormone) in conditions such as love or emotional reaction to someone or something can play a role in dilation of the pupil. Also, when you focus on a particular topic, your pupils may dilate.

Unilateral benign pupil dilatation also commonly occurs in women with migraines in which one of the pupils dilates. Pupil size returns to normal within a few hours to a few days, but you will need to see a doctor to rule out more serious problems.

Frequently Asked Questions about pupil dilation

1. How long does it take for the pupil to return to normal after taking the medicine?

This usually happens when the effect of the drug diminishes and no specific time can be set for it. Different drugs have different effects and the duration of dilation is unpredictable.

2. When to see a doctor?

If the pupil change is constant and unreasonable, you should see a doctor. If these changes are sudden and new, or occur after an eye or head injury, it may be a sign of a more serious illness. Also, if pupil dilatation is associated with a specific symptom, an emergency should be performed. These symptoms include:

  • Blurred vision;
  • Diplopia;
  • Light sensitivity;
  • Fever;
  • Headache;
  • Loss of vision;
  • Nausea or vomiting;
  • eye’s pain;
  • Neck stiffness.

3. What is the treatment for pupil dilatation?

  • If this occurs with medication, do not take the medication if possible or use an alternative medication in consultation with your doctor.
  • Dilated pupils are usually more sensitive to light than usual, so avoid bright environments.
  • Wear sunglasses or protective lenses when going out.
  • Sometimes it is necessary to repair the injury with surgery.
  • Pupil dilation can affect your vision, so consult your doctor for driving and doing risky activities.

4. What is the size of a healthy eye pupil?

2 to 4 mm in bright light and 4 to 8 mm in low light.

5. Could one pupil be bigger than the other?

Yes. This condition is called anisocoria and is a common disease in which both pupils respond naturally to light, but one pupil is more than half a millimeter larger than the other. About 20% of people have anisocoria.

6. Does anxiety cause the pupil to dilate?

Yes. Sometimes the pupil may dilate due to increased adrenaline during anxiety and stress.

7. Does the pupil of the eye enlarge when lying?

Yes. Lying can increase stress and cause the pupil to dilate.

You say

Have you ever checked the size of your pupil in front of a mirror by dimming the room light? Ever been worried about your pupils dilating too much? If you wish, you can share your experience and opinion with us and send this article to your friends through social networks.


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