How do dogs see the world?

image of tomatoes in shade of green

Dogs have many extraordinary abilities and physical attributes, including speed, sense of smell and inherited instincts to hunt and guard. Dogs, contrary to popular belief, do not see the world in black-and-white. Their vision is red-green colour blind meaning they can only see in shades of blue and yellow.

Dog Eye Anatomy

The anatomy of a dog’s eye is very similar to that of a human eye with a most of the same components.

  • Sclera: Tough, fibrous layer that’s often referred to as the “white” of the eye
  • Cornea: Thin, clear layer at the front of the eye that can be injured easily
  • Conjunctiva: Lining of the eyelids that can become inflamed and pink in color when dogs get excited, have allergies, or have an eye infection
  • Iris: Colored part of the eye that contains smooth muscle and controls the size of pupil, regulating how much light enters the eye
  • Pupil: Black area in the center of the iris; It contracts (gets smaller) in bright light or dilates (gets bigger) in dim light
  • Lens: Located behind the iris; it changes shape to focus light on the retina
  • Retina: Located in the back of the eye; it contains photoreceptors called rods, which sense light and movement, and other photoreceptors called cones, which sense colors

Dogs also have eye structures that people lack:

  • Tapetum lucidum: Located behind the retina, the tapetum lucidum reflects light through the retina, increasing the light available to the photoreceptors. This why animals see better at night, and it makes an animal’s eyes appear to glow at night when lights reflect from the animal’s eye.
  • Third eyelid: Known as the nictitating membrane, the third eyelid is whitish in color and is located at the corner of the eye, near the nose. It helps protect the eye from scratches and also moves across the eye when a dog blinks to help produce tears. Toy breeds don’t have the third eyelid.

There is some evidence that dogs may be able to see colors humans cannot. A 2014 study published in the journal Proceedings of the Royal Society B found that the lenses in the eyes of a dog transmit significant amounts of ultraviolet light, whereas these wavelengths are blocked by human lenses. This suggests that dogs might see more blue light than we do.

Field of vision

Dogs are only able to see 20 feet and that vision is likely blurry but they do not need the absolute clarity of sight that we humans have as a result of their other senses. A recent study proved via MRI that a dog’s sense of smell is linked to the part of the brain that controls vision so a mixture of senses are used to see their world.

A dog can see 250-270 degrees as compared to 180 degrees in people but lack depth perception like we do. This is also compensated by having more rods in their retinas than humans. Dogs can see 80 images per second compared to humans 60 images per second ultimately making them able to react quicker to items on a wider viewing angle.

Can dogs see at night?

While dogs’ night vision is fairly blurry, at roughly 20/250, according to the 2017 study, it is also much more sensitive than humans’ night vision. Dogs are crepuscular, meaning they tend to be most active at dawn and twilight, according to the American Kennel Club. While human eyes are chock-full of cones, which help detect colors and work best in bright daylight, dogs’ eyes contain more of the light-detecting cells known as rods, which distinguish between dark and light and thus are at their best in low-light conditions, according to the Merck Veterinary Manual

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