How do your eyes see at night?

When the sun goes down, many creatures come out of the shadows in search of a late-night meal. Cats and owls use their impeccable night vision to hunt mice and other small prey. Humans use their refrigerator light to look for something tasty, ultimately settling for shredded cheese... again. 

Okay, so night vision isn't an essential survival trait for daytime dwellers like yourself. But you have likely experienced your eyes adjusting in the dark at one point or another, so humans must have some ability to see at night, right? Let's find out. 

How well do we see at night? 

Don't compare your ability to see in the dark to The Predator's just yet. The truth is human eyes don't truly see anything at night. When your eyes adjust to the darkness, they're actually interpreting light signals and sending them to your brain so that your mind can make sense of what you're seeing. That's why something as innocent as a robe hanging up in your bathroom could scare the living daylight out of you in the dark. 

How do your eyes adjust to the dark? 

Have you ever shone a flashlight near your eyes in a dark room and looked in the mirror? You'll see your pupils (the black circle in the middle of each eye) open and close. In the dim light, your pupils open wide to enter more light. When the flashlight is shining near your eye, your pupils automatically contract. The iris, or the colored part around the pupil, regulates the amount of light your eye receives, adjusting the size of the pupil as needed. Your nerves work together to contract and expand both pupils at the same time. 

When your eyes receive light, they activate specialized cells in the back of your retinas, also known as rods and cones, to create images for your brain. Cone cells are responsible for perceiving color and fine details. When you're in an area with low light, your cones don't have much to pick up. The darker it is, the more your rod cells have to step it up in order to create images for your brain.  

Here's a cool fact: rods can only view things in black and white. They aren't able to distinguish the finer details, but the good news is, they remain incredibly sensitive even in areas with low lighting. 

Does everyone see well at night? 

When it comes to being able to see clearly at night, your mileage may vary. Certain vision problems or eye conditions can make it more difficult to see at night. These conditions include: 

Nyctalopia, or night blindness 

Diabetes 

Glaucoma 

Cataracts 

Certain vitamin deficiencies 

If you suspect you have an eye condition or have any problems with your vision, make sure to schedule an eye exam with your eye doctor. 

Now that you know why we're able to see in the dark, even though we can't truly see in the dark, we thought you might be interested in learning what babies see with their developing eyes.