How does human vision compare to a Dog, Cat and a Horse?

Dog Cat Horse

Vision is a remarkable sense that varies across different species, each adapted to its ecological niche and needs. Comparing vision in humans with other species reveals a fascinating array of visual systems and adaptations. To understand how animals see the world we must look at the anatomical differences between the species.

how animals see worldThe position of the eyes and the shape of the head determines the visual field. Predators (e.g. Humans, Dogs & Cats) have forward facing eyes with a large area of overlapping ‘binocular’ vision that allows for depth perception. Depth perception is required when predator species are pouncing on their food or playing tennis! Prey species (e.g. Horses and Rabbits) have eyes positioned on the side of their head to allow for the widest field of view, because watching out for predators is of prime importance to them.

Photoreceptors are cells in the retina that are sensitive to light. Cone photoreceptors provide high definition day-light colour vision whereas rod photoreceptors provide low definition night vision and sensitivity to movement. Predators tend to have a higher number of cone photoreceptors and prey species have a higher population of rod photoreceptors.

The majority of domestic species (except pigs) have an additional mirror-like layer behind the retina called the tapetum. This layer bounces light back onto the retina to improve sensitivity under low-light conditions. This layer gives our pets eye-shine at night and it is common to see different shades of green, blue yellow and pink.

Veterinary surgeons are often asked ”which animal has the best vision?”. However this is an impossible question to answer because the sight of every animal has evolved to suit the environment that they inhabit. A horse may be more sensitive to movement over a wide field of view under low-light conditions, whereas a bird may be able to detect Ultraviolet light that is invisible to humans.

Humans:

Our eyes are forward-facing, with 120 degrees of binocular vision that provides depth perception and a three-dimensional view. Our total field of view is approximately 200 degrees and we have three types of colour receptors (trichromatic), allowing us to perceive a broad spectrum of colours, including reds and yellows. Our vision is well-suited for activities that require recognition of fine details, and assessing the world in rich colour.

The human eye is adapted to diurnal (daytime) vision. We have a large fovea, which is an area of the retina that is densely packed with cone photoreceptors, providing high visual acuity for activities that require precise discrimination, like reading, identifying faces or driving a car. While our colour vision is highly developed, we have a less acute sense of motion detection and poor night vision compared to most other domestic animals.

Key facts Human:

  • Trichromatic
  • Total field of view 200 degrees
  • Binocular field of view 120 degrees
  • Flicker fusion 50Hz

Dogs:

How does their vision compare to ours?

simulated vision human
simulated vision dog

Dog Vision vs. Human

Dogs have a visual system that is well-suited to their role as hunters and companions. The position and size of the forward facing eyes will vary between breeds with some dogs having a longer nose than than others (Pugs vs Labradors). Most dogs will have a total visual field of 240 degrees, which is wider than the human visual field, but they only have approximately half the binocular overlap that we use for depth perception.

Dogs have dichromatic vision, perceiving the world in shades of blue and yellow. This means that dogs do not have the ability to clearly distinguish between reds and greens, as these colours fall outside their perceptual range. Dogs eyes can process more images per second than humans and this allows for a greater sense of motion detection. While their colour vision is less advanced than that of humans, Dogs excel in low-light environments, making them effective hunters and watchdogs.

Research has demonstrated that humans have visual acuity (ability of the eye to distinguish shapes and the details of objects at a given distance)that is approximately three times greater than Dogs e.g. if we are stood 75feet from an object we can clearly see, a dog would need to be 55feet closer to the object to identify the same level of detail.

Key facts Dog:

  • Dichromatic, cannot distinguish between red & green
  • Total field of view 240 degrees
  • Binocular field of view 60 degrees
  • Flicker fusion 75Hz with improved motion detection compared to humans
  • Majority of dogs do not have a refractive error
  • Rottweilers may be short-sighted
  • Visual acuity 20/75

Cats:

How does their vision compare to ours?

Human night vision
Cat night vision

Night Vision: Cat vs. Human

Cats, revered throughout history for their mysterious and enigmatic nature, possess a unique visual system. Cats are crepuscular hunters, meaning that they are most active at dawn and dusk. They have vertical slit pupils that can rapidly adjust in size depending on the level of light. Their pupils allow them to switch between near and far vision, which is a valuable trait for activities like pouncing on a toy or stalking distant prey.

Cats have dichromatic vision similar to dogs and horses, perceiving the world in shades of blue and yellow and they cannot distinguish between red & green. Cats have acute night vision is a result of the tapetum, a reflective layer behind the retina that enhances sensitivity to low light. While cats cannot see as many colours as humans, they have a wider binocular overlap, excel in detecting motion and have excellent peripheral vision.

While cats excel in night vision and motion detection, their visual acuity is not as sharp as that of humans. A cat's visual acuity is roughly 20/150, meaning that what a cat can see clearly at 20 feet, a human can see at 150 feet. However, their ability to focus on close objects, especially those within a few feet, is exceptional, aiding them in calculating precise jumps and capturing small prey.

Their visual acuity, coupled with their unique night vision adaptations, makes them exceptional hunters.

Key facts Cat:

  • Dichromatic, cannot distinguish between red & green
  • Total field of view 200 degrees
  • Wide binocular field of view 140 degrees
  • Flicker fusion 70-100Hz, excellent motion detection in the environment close to them
  • Night vision x6 better than human
  • 20/150

Horses:

How does their vision compare to ours?

simulated vision human
simulated vision horse

Horse Vision vs. Human

Horses have one of the largest eyes among land mammals. Their eyes are positioned on the sides of their heads, which, while limiting their binocular vision, grants them an expansive almost 360-degree field of view. This panoramic sight is crucial for early predator detection which is a survival trait for a prey animal. However, it comes with a trade-off in depth perception.

The pupils of horses are horizontally elongated, which enhances their ability to scan the horizon and detect potential threats. This feature also allows more light into the eye, aiding in low-light vision, although not to the extent seen in nocturnal predators like cats. While horses are not as adept at night vision as some nocturnal animals, they have better night vision than humans. Horses also have a reflective tapetum that increases the light available to the photoreceptors, enhancing their ability to see at night. However, this sensitivity to light also means that horses need more time to adjust when moving between different light levels. The transition from a bright outdoor environment to a dimly lit stable, for example, can be momentarily disorienting for a horse.

Horses have dichromatic vision and can primarily perceive the world in shades of blue and green, with limited ability to see reds and yellows. In terms of visual acuity, horses have relatively poor resolution compared to humans. Their acuity is estimated to be around 20/33, which means they cannot see fine details as humans do. However, their vision is well-suited for detecting movement and identifying large objects over a wide landscape.

Key facts Horse:

  • Dichromatic, cannot distinguish between red & green
  • Panoramic total field of view of 362 degrees
  • Binocular field of view 65 degrees
  • Horizontal (rectangular) pupil
  • Cannot see under their nose or behind their tail
  • 20/33