Dog Vision: How Dogs See
As predators who hunt prey, dogs have a unique way of seeing the world around them that is a function of their evolution. Moreover, dog eyesight has likely been influenced by the domestication process and selective breeding by humans to create breed groups that specialize in particular skills, such as the sight and scent hounds (Byosiere, et al., 2018). As humans, sometimes it is easy for us to forget that our companion animals experience the world differently than we do. Having an understanding about how your dog visually navigates their environment can help you set them up for success.
The Anatomy Of The Dog’s Eye
The anatomy of a dog’s eye is similar to humans. The orbit is the pocket in the skull where the eye is found. The eyelids open and close over the eye to protect it from debris and help keep the eye moist. Dogs have a third eyelid, called the nictitating membrane. Humans do not have this structure in their eyes. This acts as additional protection for the eyes that dogs would need because they are closer to the ground and more likely to run face first through vegetation than a human will. The optic nerve sends visual information detected by the eye to the brain, allowing the brain to communicate to the rest of the body how to respond. The sclera is also known as the white of the eye and helps to protect the eye. The conjunctiva is a membrane in the eye (this is the part of the eye that gets inflamed when someone has pink eye, also known as conjunctivitis). The cornea is the transparent dome structure in the eye over the pupil and iris. The cornea, pupil, and iris all help control light intake. The iris is the colored ring seen in eyes. The pupil is the black circle in the eye. The pupil gets bigger and smaller depending on how much light is in the environment. The lens of the eye helps the eye focus on objects, whether they are near or far away. It is found behind the iris. The retina is found inside the eye and contains photoreceptors, which detect and respond to light (Gelatt, Merck Vet Manual).
The photoreceptors are an important part of the eye and are one of the main structures responsible for differences in eyesight between dogs and humans. Evolutionarily, dogs would be crepuscular (active at dawn and dusk) or nocturnal (active at night). This means their eyes are designed to see well in low levels of light. Humans, who are diurnal (active during the day), are better at seeing in well-lit environments and are not as good at seeing in low lights. The photoreceptors consist of cones and rods. Cones are the photoreceptors responsible for color vision and rods help with vision in low light (Jacobs, 2009). Dogs have more rod photoreceptors in their eyes, with only 3% of their photoreceptors consisting of cones (human have 5%). Besides having a higher concentration of rods in their eyes, dogs have a special tissue that helps improve their vision in low light conditions. This tissue is called the tapetum lucidum. The tapetum lucidum is responsible for giving dogs that glowing look on their eyes in pictures with a flash. Many different animals have this, including cats. Humans do not have this adaptation (Byosiere et al., 2018).
Visual Development In Dogs
Puppies are born with their eyes closed and are blind until their eyes open at approximately 10-14 days of age. This helps protect the puppy’s eyes until they are more developed and are able to deal with bright lights and risk of debris getting into their eyes. When puppies first open their eyes, their vision is still developing. They primarily rely on scent and sound to get around and find their mother since they mostly just see shapes and movement. Young puppies will typically have blueish-grey irises which change to brown when the puppy is about 8 weeks of age. By 8 weeks of age, the puppy’s eyes have fully developed, and they have the vision of an adult dog (Coren, 2009).
Can Dogs See Color?
It is believed that dogs can see color although there is evidence to suggest that they cannot see as many colors as humans (Byosiere et al., 2018).
Why Are Dogs Only Able To See Certain Colors?
Researchers believe that dogs can see fewer colors than humans because they have fewer types of cone receptors in their eyes than we do. Humans have three types of cone receptors in their eyes that allow them to see red, green and yellow. This is known as trichromatic vision. Dogs have two types of cone receptors that we believe allow them to see blue and yellow, known as dichromatic vision (Byosiere et al., 2018).
What Colors Can Dogs See?
Evidence suggests that dogs can see hues of blue and yellow, and are unable to distinguish between red, green, and yellow (Byosiere et al., 2018). This is perhaps why sometimes dogs cannot see objects we throw for them out in the grass. For example, if you throw a green or red ball outside, your dog may have a hard time finding it. It is best to get your dog a bright yellow or a blue ball to play with.
Do Dogs Have Night Vision?
Dog eyes are specially developed to be able to see in low light environments, making them much better at seeing in the dark than humans can. However, there needs to be a small amount of light for their vision to work. This means that dogs cannot see in complete darkness. Therefore, dogs do have night vision of sorts, as long as there is some sort of light in the environment.
How Is A Dog’s Vision Beneficial To Their Survival?
Dogs evolved to be crepuscular (active at dawn and dusk) or nocturnal (active at night), so their vision is optimized to see in low light conditions. Being able to see in low light environments is beneficial to their survival because it allows them to find prey and evade predators during their active periods where little light is available (Byosiere et al., 2018).
Do All Dogs Have The Same Vision Setup?
There is some evidence to suggest that vision may vary between dog breeds, and possibly within dog breeds. However, there is little research done on this topic, therefore we do not know for certain (Byosiere et al., 2018).
What Are The Differences Between Human Vision Versus Dog Vision?
There are many differences between human and dog vision that are important to keep in mind as dog owners. Here are some of the differences outlined in a review on dog vision by Byosiere and colleagues (2018):
- If you go into a dark space after looking at a bright light or being out in the sun, you may temporarily have poorer vision as your eyes adjust to the light conditions. This is known as the photo bleaching effect. It takes dogs twice as long as humans to regain full vision after coming inside the house when it is bright outside. It may take humans 30 minutes for their vision to return to normal, and dogs almost an hour.
- Dogs have worse visual acuity than humans. They can see an object clearly at 20 feet away that a human can see clearly at 75 feet away.
- Humans can see more colors due to three different types of cone receptors in our eyes. Dogs only have two types of cone receptors.
- Dogs may be able to see ultraviolet light to a certain extent, but more research is needed on this.
- Dogs have a receptor in their eye that may help cue them in to the magnetic field of the earth.
Can Dogs Lose Their Sight As They Age?
Yes, just like humans, dogs can lose their eyesight as they age. This can become a major problem for the dog and the owner. Some elderly dogs may develop cloudy looking eyes that get worse as they age. Some pet parents may notice this as the first sign their dog is losing their vision, but there can be other symptoms as well. Dogs may become more hesitant and careful when walking around the house and jumping on and off furniture. They may be more nervous to go down the stairs, especially if there is low light. Dogs losing their sight may also bump into furniture, become jumpy, anxious, or clingy, and some may even become more aggressive as a defense mechanism for not being able to see as well (Gibeault, 2017).
There are some ways to help your senior dog navigate the house better as they age. You can use scent markers on important places in the house to help them find their way around, such as spraying perfumes or other scents by the food and water bowls or by the door to go outside to go potty. You can also reduce clutter in their typical paths around the house and avoid moving around or putting in new furniture. This will reduce the risk of them bumping into things and make them feel more comfortable. Providing mats or rugs where they typically walk, go down the stairs, or jump off furniture can help them better visually assess their surroundings and give them more confidence. For older dogs losing their eyesight, it is also important to provide plenty of light in high traffic areas, especially on stairs and to speak to them often so they know where you are and do not get startled when you approach them (Gibeault, 2017).
Dogs are great companion animals and truly are human’s best friend that provides many benefits and lots of laughter and joy. It is important that dog parents provide them the best environment they can to let them thrive. Understanding how a dog sees the world around them gives us the opportunity to set them up for success living in a human world. Dog vision is different than our human vision. Dogs cannot see as clearly as we can and cannot see as many colors. However, dogs have great vision in low lights and might be able to see things that we cannot. As your dog ages, you may notice changes in their vision and behavior, but there are plenty of ways you can help your dog feel comfortable and safe in their old age.
Byosiere, S.-E., Chouinard, P.A., Howell, T.J., and P.C. Bennett. 2018. What do dogs (Canis familiaris) see? A review of vision in dogs and implications for cognition research. Psychonomic Bulletin & Review 25(5):1798-1813.
Coren, S. 2009. Why are puppies born with their eyes and ears closed? Psychology Today. Accessed on December 12, 2019.
Galatt, K.N. Eye structure and function in dogs. Merck Veterinary Manual. Accessed on December 12, 2019.
Gibeault, S. 2017. Vision loss in senior dogs – symptoms and management. American Kennel Club. Accessed on December 12, 2019.
Jacobs, G.H. 2009. Evolution of colour vision in mammals. Philosophical Transactions of Royal Society B 364(1531):2957-2967.