How does night vision work ?


Also referred to as scotopic vision, is your natural ability to see in the dark.

In a dark room or outside at night, your eyes like to gather as much light as possible so that they can translate the images in front of you to your brain. Your eyes are able to do this by widening your pupils which means that more light and shapes can enter.


Want to test this? Stand in front of a mirror and switch the light off for a minute. Make sure your eyes are completely closed. Then, still with your eyes closed, switch on the light. Whilst facing the mirror, open your eyes and you will see your pupils shrink! This is because in a brighter setting your pupils have enough light for your eyes to see, so they don’t need to be bigger.


But, it’s not just the pupils that make you able to see in the dark. For that, you have to look at the microscopic cells in the back of your eyes. There are millions of rod-shaped and cone-shaped cells on every eye’s retina and without them, we wouldn’t be able to see.


Cones register bright lights, colours and fine details, and rods help you to see in darker settings because they are more sensitive to light. However, rods don’t process colour - hence why in the dark you don’t see many colours.



Do humans have good night vision?

In comparison with animals, humans don’t have the best night vision abilities. One reason for this is because our eyes take a long time to adjust to a dark setting - about 40 minutes!!


This is because humans don’t need to see in the dark because we are usually asleep at night and awake during the day. Animals that are nocturnal or spend more time in the dark tend to have better night vision. Have you noticed that cats and dogs eyes’ look reflective at night? That is because they have an iridescent coating behind their retina that boosts night vision abilities.



Eye diseases that can affect night vision :

Some eye conditions can make it very hard to see in low light, which is a symptom called nyctalopia (night blindness).


Different levels of night blindness can be caused by:


  • Nearsightedness
  • Cataracts
  • Diabetes
  • Glaucoma
  • Retinitis pigmentosa
  • Glucose or vitamin A imbalances


If you’re experiencing problems with your vision at night and in the dark, you should book an eye exam so an optometrist can check your overall eye health.