Particle 101: Eyeshine

What causes some nocturnal animals to have reflective eyes?
Tom Gurn
Tom Gurn
Freelance Writer
Particle 101: Eyeshine
Image credit: u/oldburgerguy via

Have you ever jumped at the sight of two glowing white orbs outside your bedroom window?

Have you ever noticed your pet’s eyes appear to flash brightly at night or in a photograph?

This phenomenon, known as eyeshine, is caused by something called the tapetum lucidum. It’s a feature in the eyes of many vertebrates, including felines both big and small and most breeds of dogs.


In the human eye, light waves are first focused through the exterior dome-shaped cornea. From there, the coloured section of the eye, called the iris, will either expand or contract to let more or less light through.

After that, a lens focuses the light onto the retina, which is the light-sensitive tissue that lines the back of the eye. There, specialised cells will at last convert the light into information to be transmitted to the brain. This forms the images we see inside our heads.

Humans are diurnal, meaning we prefer to operate during the daytime. The eyes of nocturnal animals have an additional component. The tapetum lucidum is situated behind the retina and made of tiny reflective crystals, causing their eyes to flash up brightly at night.


This effect is often confused with the red-eye effect that people sometimes display in photos. But that’s caused by the red blood vessels in the back of the eye getting caught in the camera’s flash.

However, eyes equipped with tapeta can light up red, blue, green or many other colours. This can depend on the presence of certain minerals like zinc and riboflavin or even the age of the animal. So two dogs of the same breed can have different coloured eyeshine.

Thylacine, or Tasmanian tigers, are said to have had a pale-yellow eyeshine. This is utilised by modern-day thylacine hunters who attempt to confirm potential sightings through the colour of distant eyeshine.


The tapetum lucidum reflects light waves back onto the retina a second time, which allows the light-sensitive tissue another chance at taking in the information.

It’s what enables nocturnal animals to see so well in the dark and what sends light waves ricocheting around the eyeball and back out through the pupil.

It’s not all superpowers for nocturnal animals however. Having tapetum lucidum comes with some trade-offs. Studies suggest that all of those light waves bouncing around may cause the image to become blurry and unclear.

This might be why your cat always thinks your toes are prey when you get up for a snack in the middle of the night.


Forget eating carrots. Humans will never catch up to tapeta-sporting animals at night vision. But that doesn’t mean we can’t use it as inspiration.

The biological structure is the muse of the cat’s eyes plastic reflectors lining our highways. So even though we can’t see as well in the dark, at least the tapetum lucidum helps guide our way at night.

Tom Gurn
About the author
Tom Gurn
Tom Gurn is a freelance writer from Kaurna Yerta (Adelaide), South Australia
View articles
Tom Gurn is a freelance writer from Kaurna Yerta (Adelaide), South Australia
View articles


We've got chemistry, let's take it to the next level!

Get the latest WA science news delivered to your inbox, every fortnight.


Creative Commons Logo

Republishing our content

We want our stories to be shared and seen by as many people as possible.

Therefore, unless it says otherwise, copyright on the stories on Particle belongs to Scitech and they are published under a Creative Commons Attribution-NoDerivatives 4.0 International License.

This allows you to republish our articles online or in print for free. You just need to credit us and link to us, and you can’t edit our material or sell it separately.

Using the ‘republish’ button on our website is the easiest way to meet our guidelines.


You cannot edit the article.

When republishing, you have to credit our authors, ideally in the byline. You have to credit Particle with a link back to the original publication on Particle.

If you’re republishing online, you must use our pageview counter, link to us and include links from our story. Our page view counter is a small pixel-ping (invisible to the eye) that allows us to know when our content is republished. It’s a condition of our guidelines that you include our counter. If you use the ‘republish’ then you’ll capture our page counter.

If you’re republishing in print, please email us to let us so we know about it (we get very proud to see our work republished) and you must include the Particle logo next to the credits. Download logo here.

If you wish to republish all our stories, please contact us directly to discuss this opportunity.


Most of the images used on Particle are copyright of the photographer who made them.

It is your responsibility to confirm that you’re licensed to republish images in our articles.


All Particle videos can be accessed through YouTube under the Standard YouTube Licence.

The Standard YouTube licence

  1. This licence is ‘All Rights Reserved’, granting provisions for YouTube to display the content, and YouTube’s visitors to stream the content. This means that the content may be streamed from YouTube but specifically forbids downloading, adaptation, and redistribution, except where otherwise licensed. When uploading your content to YouTube it will automatically use the Standard YouTube licence. You can check this by clicking on Advanced Settings and looking at the dropdown box ‘License and rights ownership’.
  2. When a user is uploading a video he has license options that he can choose from. The first option is “standard YouTube License” which means that you grant the broadcasting rights to YouTube. This essentially means that your video can only be accessed from YouTube for watching purpose and cannot be reproduced or distributed in any other form without your consent.


For more information about using our content, email us:

Copy this HTML into your CMS
Press Ctrl+C to copy