A dog's tapetum lucidum causes their eyes to "glow"
The essentials
- Dogs see light and movement far better than humans — Dogs have more cells called rods in the retina (back of their eye) that are responsible for collecting light.
- Canine eyes have adaptations for improved night vision — Most dogs have a reflective layer on their eye called a tapetum lucidum, which magnifies incoming light.
- Dogs don’t distinguish details or colors as well as humans — Contrary to popular belief, however, most dogs aren’t completely colorblind.
Do dogs have night vision?
For most people, the term “night vision” conjures images of high-tech night-vision goggles. Unfortunately, dogs don’t have that awesome ability to see in pitch black or total darkness. They can, however, see much better than humans in low-light situations.
There are certain parts of dogs’ eyes, different from human eyes, that have specially adapted for improved vision at night. Learning how a dog’s eye works can help owners better understand their pet’s sight capabilities in different circumstances.
Here's how dogs see in the dark
While the eyes of a dog are like those of human beings in form and function, there are several key differentiators that give our furry friends an edge. In both humans and dogs, the retina of the eyes contains photoreceptor cells, which respond to light. These cells are called rods and cones. Generally, rods function in collecting dim light, while cones are responsible for color vision. In canines, the retina consists mainly of rods and fewer cones. The result is a dog’s improved vision at night or in low lighting, but a diminished ability to differentiate colors and fine details.
Another factor responsible for our pups’ superiority over human vision is the tapetum lucidum. This reflective layer is located in the top half of the back of the eye and aids in magnifying light. When light hits the tapetum lucidum, you’ll see a greenish glint. This is the reason why many dogs’ eyes shine at night. But some dogs, especially those with blue eyes, don’t have a tapetum at all. Commonly, dogs with no tapetum will appear to have red eyes in photos due to the visualization of the eye’s blood vessels.
While it doesn’t impact low light vision, dogs also have a unique feature called a nictitating membrane, or third eyelid. Found in the inside corner of the eye, this eyelid extends to protect dogs’ eyes from irritation and trauma. It may also be seen in response to inflammation or some eye diseases.
Does my dog need a nightlight?
Many pet parents care for their pups as one of their own children. However, dogs and human infants have very different needs. For example, a nightlight is commonplace for children’s bedrooms. Dogs, on the other hand, usually don’t need any additional light beyond the natural light in your home, even at night. If your home gets especially dark, you can consider a small night light to help your pet navigate more easily in the dark. But, most dogs will do just fine without additional lighting at night.
Just like in humans, most dogs’ vision does worsen with age. Some develop lenticular sclerosis, which causes a bluish-white haziness in the lens. These are different from a cataract but still affect vision. Geriatric dogs with lenticular sclerosis often struggle with night vision, so a night light could be helpful in these cases.
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Anatomy of a dog’s eye
Animal ophthalmology (the study of canine eyes) can be a tricky topic, with many scientific names to decipher. In truth, dog eyes are quite similar to human eyes in several ways. Knowing how to recognize each individual part of the eye can help owners better identify when something seems wrong or out of place.
- Orbit. This is the bone cavity or “eye socket” which holds the eyeball. It contains muscles, nerves, blood vessels, and tear ducts.
- Sclera. The sclera is the white outer surface of the eye.
- Conjunctiva. This thin mucous membrane lines the eyelid and covers the sclera.
- Cornea. The cornea is the clear outer layer of the eye. It both protects the eye and helps focus incoming light to the retina.
- Iris. The round, colored part of a dog’s eye. The iris can make the pupil larger or smaller, controlling the amount of light entering the eye.
- Pupil. The small dark area in the center of the eye. In low-light situations, the pupil will enlarge to let more light in. Conversely, it will contract under bright light.
- Lens. Found behind the iris, the lens changes its shape to allow light into the retina. Ciliary muscles in the eye either contact or relax to help the lens focus on nearby or distant objects.
- Retina. Important to a dog’s vision, the retina contains photoreceptor cells that sense light.
- Optic nerve. The bundle of nerve fibers known as the optic nerve is the bridge between the eye and the brain. Images from the photoreceptors are converted into electrical impulses, which are then carried to the brain by the optic nerve.
A commonly held misconception is that all dogs are colorblind. But dogs can see color , just not as well as humans. Dating back to the evolution from wild wolves, dogs developed larger lens and corneal surfaces, plus the tapetum membrane discussed above. The purpose was to improve night vision for hunting in the dark. To this end, dogs also developed more rod photoreceptors than cones, which help improve low light vision in the retina. One result of this, however, was the presence of fewer cone receptors, responsible for color vision.
Dogs are considered dichromatic, meaning they only have two types of cones, while most humans have three. For this reason, many dogs view the world in a similar way as people with red-green colorblindness. This means they can’t easily tell the difference between red and green. But, they can see blue and yellow well.
👉 Check out the Dog Vision image processing tool for a unique perspective into how dogs’ vision differs from our own.
Frequently asked questions
Do dogs have night vision?
While dogs can’t see in total darkness, they do have much better night vision than humans. This is due to their rod photoreceptors and a light-reflecting layer called the tapetum.
Are dogs afraid of the dark?
Most dogs have adapted well to low-light situations. Some, however, like those with eye diseases or those going blind, may experience some challenges in darkness. Generally, dogs should have no reason to fear the darkness alone.
Is it OK for dogs to be in the dark?
You might feel bad about leaving your dog in the dark, but they likely don’t mind. Many dogs are fine with natural light, even at night, but you can consider a small night light if your home is especially dark, or if your dog is geriatric.
