Have you ever wondered whether you can tell what someone is thinking just by looking into their eyes? Some studies have revealed that our emotions can contribute to the dilation and constriction of the pupils – an entirely involuntary action controlled by the autonomic nervous system.
You may even have heard that dilated pupils can be a sign that someone likes you. But is it true? Our experts at Lenstore have put together a list of the reasons why our pupil size can change, and the possible meanings behind this involuntary reflex.
Why do pupils dilate when you look at someone you like?
The autonomic nervous system has various responses when we experience emotional arousal – such as physical excitement or happiness. The “happiness hormone” dopamine is produced when the body anticipates something good, like a slice of cake or the attention of someone we care about. As a side effect, this hormone can also cause the pupil to widen. When you look at someone you love and notice that their pupils are dilated, it could be a sign that their feelings for you are just as strong.
What other emotions can cause your pupils to dilate?
Physical excitement and love are not the only emotions that can cause your pupils to enlarge. Other emotions such as anger, fear, and anxiety can also dilate the pupils. In response to these emotional states, the pupil may widen to better evaluate any threat or risk – similar to how an animal’s pupils dilate when preparing to fight or flee.
Other causes of pupil dilation
Known by the medical term mydriasis, pupils can dilate without any change in light or emotional stimulus. The cause may be the use of certain medications, injuries, or illness. Here are some of the most common reasons that can cause mydriasis:
Medication
Some prescription and over-the-counter medications can cause pupil dilation, as they affect the iris muscle that controls the pupil. Medications that can cause this include:
- Medications containing botulinum toxin, such as Botox
- Antihistamines
- Parkinson’s disease medications
- Anti-nausea medications
- Atropine
- Anticonvulsant drugs
Eye injuries
Blows or damage to the nerves of the iris muscles that control the pupils can cause them to dilate and take on an irregular shape. This type of injury can result from complications during eye surgeries, such as corneal transplants or cataract removal.
Brain injuries or conditions
Following a head injury, stroke, or tumour, the brain may experience increased pressure, which can damage the iris muscles and cause the pupils to open and close erratically. It may affect one or both eyes, and in either case the pupils may remain dilated and unresponsive to light.
This is why, during an eye examination, a doctor or nurse will perform a torch test to check whether the pupils respond by constricting. It’s also the reason doctors check an athlete’s pupils with a small torch after a head injury during a sporting event.
Recreational drug use
Illegal substances such as cocaine, amphetamines, LSD, or ecstasy can cause the pupils to widen and reduce the eye’s ability to respond to light. During the process of withdrawal from these substances, the pupils may remain dilated.
Adie’s pupil
Adie’s pupil, also known as a tonic pupil, is a rare neurological condition in which one pupil is larger than normal and does not constrict – or responds very slowly – to bright light. There is no cure for Adie’s pupil, and in most cases its cause is unknown.
Congenital aniridia
Congenital aniridia is present from birth and typically affects both eyes. This rare condition involves the total or partial absence of the iris. As a result, the eye cannot regulate the amount of light that enters, which can cause light sensitivity and cause the pupils to widen.
Congenital aniridia may be accompanied by other serious visual problems such as glaucoma, optic nerve disorders, and nystagmus.
Benign episodic unilateral mydriasis
Benign episodic unilateral mydriasis is a harmless condition in which only one pupil dilates. Generally accompanied by blurred vision, headaches, and eye pain, it is called benign because it is not associated with any serious illness.
This condition typically resolves on its own without treatment, with the pupil returning to its normal size within a few hours – though it can last several days.
When to see a doctor about dilated pupils
In most cases, dilated pupils are not a cause for concern. But they can occasionally indicate something more serious. If your pupils are enlarged and do not respond to bright light, it’s best to get checked by a doctor or eye care professional.
Seek emergency help immediately if you or someone else has received a blow to the head and the pupils appear dilated – especially if one pupil is more dilated than the other.