Have you ever wondered if dogs have night vision? Maybe you've noticed how your pooch can effectively maneuver around the house in darkness while you manage to trip over everything. Dogs are, after all, natural predators; so it makes sense they've hung on to some of those evolutionary traits. But just how good do they see in the dark?
At a Glance:
- Dog's have 5x better night vision than humans, while cat's have 6x better vision. But that doesn't mean you should leave the lights off.
- Dog's still cannot see in total darkness, and their ability to see deteriorates with age.
- While human vision is 20/20, a dog's vision is 20/75 - meaning their long distance vision is poor.
Comparison: Dogs vs Cats vs Humans
Studies have shown that compared to humans, the average dog can see five times better in the dark than a human, while cats can see six times better. What makes their vision better in the dark? Well, we see objects by the light reflecting off of them, when that light is reduced it's more difficult for our eyes to process what's infront of us. But for dogs; they only require 1/5th the amount of light to see clearly in the dark.
Perfect human vision is called 20/20, meaning you can clearly read your typical eye chart from 20 feet away. 20/30 vision is considered worse, where from standing 20 feet away you can read letters most people can see from 30 feet away.
Dogs have 20/75 vision, meaning their long distance vision (compared to us) is poor. But while they might not be able to make out finer details from afar, they still have a very good sense of movement, sound, and smell to assist them.
Dogs also have a wider field of view than humans. A field of view is how much we can see without turning our heads or moving our eyes. A human’s field of vision is about 190 degrees, whereas a dog’s field of vision is much larger at 250 degrees. This is mostly due to placement of the dog’s eyes on the head, or where they are positioned.
The Anatomy of the Eye
So how can fido see with just one fifth the amount of light? It has to do with the basic structure of the eye; their pupil can dilate, or expand, much more than a human’s can.
We use two different types of vision receptors: cones and rods. Cones allow us to process color, while rods process light and dark.
Dog’s eyes have evolved over time to allow more rods to catch the low light as well as movement. This is so their ancestors could hunt at night with only the moon as a light source. Movement and low light visibility are all wolves needed when they hunt their prey, and it is much more useful to be able to catch the light and movement over seeing the entire color spectrum in bright light. (source)
However, your dog has less Cones, which contributes to their poor vision and inability to see a full spectrum of color.
The Truth About Color Blindness
It's a common myth that dogs can only see in black and white, but just isn't true - they do in fact see color! But just a little differently than us humans.
While dogs have the advantage of more rods and superior night vision, they only carry two types of color detecting cones - while humans have three. This allows us to see more wavelengths on a color spectrum. But for dogs, they can only see a spectrum of yellow, blue, and violets, whereas red, green, and orange are indistinguishable.
Why Your Dog's Eyes Glow
I'm sure you've noticed that when light hits your dogs eyes just right you can see a green shine reflecting back at you (often with creepy results). What you're seeing is called the Tapetum, and it's one of canine's evolutionary advantages.
When our eyes process light, it has one chance to enter our photoreceptors to be processed. But dog's get a second chance by mirroring light off their Tapetum (located at the back of the eye) and back into their photoreceptor. This secondary process gives them improved night vision.
Although it’s ideal in a dim environment, this process of reflection also scatters light, which causes some overall degradation of their vision (and the reason for their 20/75 vision). (source)
How Age Affects Vision
As dogs age their eye sight deteriorates over time as a result of retinal degeneration or cataracts. The age of onset or degradation is different for each dog, and some dogs may not experience this until much later in life. Lose of vision can be affected by infection, genetics, injuries, as well as age. There are methods that can help sustain good vision, speak with your veterinarian for more information about blindness in dogs and how it can affect older dogs.
Cataracts are a somewhat common development in older dogs, and are opacities in the lens of the eye which don’t allow light through causing lack of vision. As it enters late stages your dog will only see shadows. The lens of their eyes develops a slightly hazy tint of blue, however a blue tint does not always point to Cataracts.
Nuclear Sclerosis is a age related symptom also causing the lens to become hazy, but ultimately does not affect vision. Owners might confuse Cataracts for Nuclear Sclerosis because of the similar hazy, blue tinted eyes. But the only true way to know for sure is to have an eye examination done from your vet.
Do Different Breeds Have Different Vision?
Technically speaking, there are some differences. Some breeds have better eye genetics than others, which means they are predisposed to having better eyesight than say a dog who went blind at two years old because of juvenile cataracts. And certain breeds are more prone to losing their vision or developing eye problems.
Besides visual problems caused from aging or disease, there's no indication that different dog breeds (or even wolves) have varying levels of visual feedback. Visual aides for hunting (like night vision and a wide field of view) have descended for their predator wolf ancestors unto dogs, and there's nothing to say that different breeds have inherited anything different.
Eye Exams for Your dog
Your vet can look at your dog’s eyes during their annual examination to see if any cloudiness or opacities have occurred. This is especially important as they reach an elderly age.
Vets can perform a series of tests (called an Ophthamlic Exam) by checking pupillary light reflex, tear production, and their ability to follow an object or maneuvre around the room. The lens will also be inspected for abrasions or cataracts.
Finally, owners of breeds susceptible to eye problems, or registered breeders can use a much more in depth test called CAER (USA and Canada). CAER stands for Companion Animal Eye Registry and is a database that allows breeders and owners to have more information on trends in eye disease and breed susceptibility.
Leave The Light On For Your Dog
So what should we take away from this? Don’t leave your dog in total darkness, although they have better night vision - it's not perfect. Keep in mind older dogs may not see as well.
Leaving the house for the evening? Leave a light on, or plugin a few simple nightlights so they can find their way around easily.
Finally, older dogs are more susceptible to vision loss, so have your vet inspect their eyes during their annual checkup.