Dilated Pupils

What are Dilated Pupils?

Dilated pupil is a condition when the pupil starts expanding.  Usually, after entering a dim light room, the pupils dilate so that more light can enter the eyes. It happens due to variations in the light.

What is Mydriasis?

Mydriasis is a medical term for dilated pupils. If the pupils dilate without any specific reason, it might indicate Mydriasis. The condition is also known as “Blown Pupil.”

As estimated, 1 in 5 people are born with different sized pupils, and their eyes reflect typically with the changing light. This condition is often called ‘Anisocoria’ or ‘Physiologic.’ Nevertheless, the dilated pupil isn’t a serious problem to worry about, but a person should consult a doctor instantly if the condition persists.

What causes Mydriasis?

Mydriasis occurs because of an injury, psychological factors or even when someone is on drugs. Some common causes are:

Injury to the eye

Any injury to the eye may result in damaging the pupils or the iris. The injury will cause the change in the normal response to the varying levels of lights. Other symptoms vary according to the injury.

Brain injury

Usually, a brain injury causes increased intracranial pressure, which in turn affects the eyes. Tumor, trauma injury or a stroke may cause restlessness. Mydriasis caused by a brain injury is called “Blown Pupil.”

Use of Drugs

High-dose drugs such as cocaine, Hallucinogenics, LSD, etc. causes severe damage to the pupils. Drugs usually weaken the immune system along with liver damage and heart failures. If high on drugs, one might lose their vision.

Benign Episodic Unilateral Mydriasis

The condition leads to the dilated pupil in only one eye. Along with it, an individual may suffer from regular headaches, pain in the eyes and even blurred vision. Although it is not a situation to worry about, it requires thorough care and examination. Benign episodic unilateral Mydriasis (BEUM) also occurs during a migraine headache.


A few medicines might affect the eye nerves, causing pupils breakdown. These medicines have their side-effect in the form of dilated pupils. The medicines that might affect the eyes are:

  • Botulinum Toxin
  • Decongestants like Pseudoephedrine
  • Atropine (Used for heart diseases, stomach issues)
  • Dimenhydrinate (Used for motion sickness and Nausea)
  • Phenobarbital and Topiramate (Anti-seizure drugs)
  • Antihistamines like Diphenhydramine
  • Anticholinergics (Used to block neurotransmitters with patients having COPD or urinary incontinence)

Cranial Nerve Neuropathy

Cranial nerve neuropathy occurs when the nerves connecting to the eye are damaged. It can happen in one or both the eyes. An impaired vision is a very common result of this situation.


It’s strange but true that some plants can also cause dialated. A person might get in touch with these plants including jimsonweed, angel’s trumpet as well as the members of belladonna family. Beware of such plants!

High on Oxytocin

When the level of Oxytocin increases in the body, it might result in mild dilation of pupils. Oxytocin is a chemical released from the body after exercising or dealing in physical interactions with social people. It also plays an important role during the childbirth. It may even cause increased emotional attachment along sexual arousal.


It usually happens that when one concentrates, the pupils get dilated. There is a practice known as ‘pupillometry’ which analyzes emotions that makes the pupils dilated.

Signs & symptoms

  • Confusion or stress
  • Dry mouth
  • Vomit
  • Rapid heart rate
  • Muscle weakness
  • Paralysis
  • Seizure
  • Pain in eyes or a severe headache
  • Loss of sensation
  • Behavioral changes

Note: Seek instant medical care if you see any of these symptoms.


Treatment varies based on the cause. In some cases, a person needs surgery while in some, use of contact lenses or light-sensitive sunglasses works. So, it is important for you to know the exact cause in order to seek proper medical treatment. It’s better to consult an eye specialist if your eyes cause any problem.


Many of the injuries and trauma, followed by the dilated pupil can result in severe complications. Some of the serious issues that might happen are:

  • Coma
  • Shocks
  • Serious vision problems
  • Paralysis
  • Problems in speech
  • Seizures
  • Changes in behavior


  • Avoid sunlight
  • Do not drive during daytime
  • Make sure you use the sunglasses when going out in the sun
  • While reading a book or any text, maintain a decent distance
  • Contact the doctor instantly if your eyes stay dilated for more than 24 hours

When to see a Doctor?

It’s better to consult a doctor as soon as one finds any symptom of Mydriasis. They will review the condition and prescribe accordingly. In several cases, the doctor might ask for a blood test also. The doctor might also test the vision and clear out the exact condition.


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