Eye Health Central

Dilated Pupils: What's Going On Behind Those Big Beautiful Eyes?

Is it love, lack of light or something more sinister?

Have you ever looked in the mirror and noticed your pupils looking like big black saucers even when it's not dark? Or maybe you've been chatting to someone else and noticed their eyes and their pupils are just huge. You might be wondering why, well, let’s dive into everything about dilated pupils, why it happens, what it means and, is it serious.

What are Dilated Pupils? 

Your pupil is that black circle in the center of your eye. It's actually a hole that lets light into your eye (pretty cool, right?). When we say your pupils are dilated, it means that this hole has gotten bigger. Normally, your pupils change size to control how much light gets into your eye - they get smaller in bright light and bigger in the dark.

Dilated pupils

Why do your Pupils Dilate? 

There are a bunch of reasons, and not all of them are cause for concern. Let’s break it down:

1. Light Levels: This one's pretty straightforward. In low light, your pupils dilate to let in more light. That's why they're bigger at night. It's your body's way of helping you see better in the dark.

2. Emotions: Ever heard that your eyes are the window to your soul? There’s some truth to that. Strong emotions like excitement, surprise or attraction can cause your pupils to dilate. It's like your body's natural reaction to things that essentially get your heart racing.

3. Medications and Substances: Certain medications, drugs, or substances can cause your pupils to dilate. For example, some decongestants, antidepressants, and even caffeine can have this effect. Illegal drugs, especially stimulants like cocaine or MDMA, are also known for causing dilated pupils

4. Eye Exams: The eye exam itself should not make your pupils dilate, however, your optometrist might put drops in your eyes that make your pupils dilate. This is done on purpose so the doctor can get a better look inside your eyes.

5. Brain and Nerve Issues: Sometimes, dilated pupils can be a sign of a more serious problem, like a brain injury, a stroke or an issue with your nervous system. If your pupils are dilated and you can't figure out why, or if you have other symptoms like a headache, dizziness or trouble speaking, you should see a doctor immediately.

6. Eye Health: Certain eye conditions, like glaucoma or an eye injury, can also cause your pupils to dilate. If you're experiencing pain, vision changes or you've injured your eye, get it checked out.

7. Benign Episodic Unilateral Mydriasis: Now, that's a mouthful, isn't it? Let's break it down. This condition is like a random party trick your eye pulls off. It means one of your pupils (unilateral) suddenly decides to dilate (mydriasis) for a short time (episodic), and thankfully it's usually nothing serious (benign). Imagine looking in the mirror and seeing one pupil bigger than the other. Freaky, right? But often, it's just your eye being a bit dramatic. This is often caused by migraines, but stress and fatigue can also trigger it. If this happens, keep an eye (pun intended) on how often it occurs and if it's accompanied by other symptoms, if you also experience, headaches, blurred vision etc then seek medical advice. If it's just a once-in-a-while thing and you feel fine otherwise, it's probably no biggie.

8. Adie's Pupil: This condition is a bit like your eye not following the rules. Adie's pupil (also referred to as tonic pupil) is where one pupil reacts slower to light changes or doesn't react much at all. It might also be bigger than the other pupil. But why does this happen? It's usually due to a disruption in the nerve connections that control your eye muscles. The cause however is often a bit of a mystery, but it could be from an infection or injury. The quirky thing about Adie's pupil is that it can make one of your eyes look like it's always ready for a dimly lit romantic dinner, even in bright sunlight. It's usually not serious but if you notice this happening it is worth mentioning to your doctor, just to rule out other issues.

9. Congenital Aniridia: Aniridia means no iris. The iris is the coloured part of your eye that makes your pupil look smaller or larger. So, if you have congenital aniridia, you’re missing all or part of your iris from birth. This doesn't just mean your pupils look bigger, it can also affect your vision since the iris controls how much light enters your eye. People with congenital aniridia might be sensitive to light or have other vision issues. This condition can be part of a genetic syndrome, so it's definitely something that gets checked out early in life.

What should you do if you notice your Pupils are Dilated

• If it's dark out, or you're feeling strong emotions, it's probably nothing to worry about.
• If you've taken a new medication, or substance and notice a change, check the side effects or talk to a healthcare professional.
• If your pupils are uneven (one big, one small) for an extended period of time, that’s a red flag. It could be a sign of a more serious condition, so you should see a doctor as soon as you can!
• If you have other symptoms like a headache, vision problems, or if you've hit your head recently, get medical help right away. It's better to be safe than sorry.

Why do Doctors, check Pupil Reaction

Dilated pupils are a fascinating part of how our bodies work. They can tell us a lot about what's going on, both inside and out. If you have experienced a bang to your head or ended up in casualty following an accident or an incident with medication you may notice the doctor shines a light into your pupils. By using the PERRLA test doctors can determine if there are signs of eye disease or point to conditions that can affect your nervous system or brain.

What does PERRLA mean

PERRLA is a test doctors or nurses carry out to determine the reaction of your pupils, and it is an acronym Pupils are Equal, Round and Reactive to Light and Accommodation. So they are checking that your pupils are

Equal: Pupils should be equal in shape and size.
Round: Healthy pupils are round.
Reactive to Light and Accommodation: Healthy pupils get smaller in bright or direct light, and when a person focuses on something very close to their eyes.

Having large pupils is normally just your body reacting to the world around you. But if something feels wrong or you've banged your head, don't ignore it. Your eyes aren't just the window to your soul, they are also a pretty good indicator of your overall health. Remember, taking care of your eyes is a big part of taking care of you. 

Author: John Dreyer Optometrist Bsc(Hons), MCOPTOM, DipCLP
Created: 28 Nov 2023, Last modified: 20 May 2024