How well do pets see?
A quick guide to understanding our pets' vision
Vision is comprised of several elements:
- field of view
- depth perception
- perception of motion, and
- color differentiation,
all of which are integrated in the brain to produce useful vision.
Field of view
Pets' eyes are set wide on their heads, so their field of view is 60-70° larger than the human field (humans see 180°, while pets can see closer to 240°). This is possible because both dogs and cats have their eyes set at about a 20° angle to increase perpheral vision. Although humans can see objects 3 inches from their noses, pets generally can't see objects any closer than 1 or 2 feet from their noses -- they use their noses and whiskers to identify close objects.
The central, binocular field of vision of pets -- the vision field seen simultaneously by both eyes -- is less than half that of humans, so pets have very limited depth perception and are therefore less able to accurately judge distances.
Acuity is the ability to focus and clearness of vision, measured in people using an eye chart and in animals using retinoscopy. Humans have about 1.2 million optic nerve fibers; dogs and cats only have about 150,000 optic nerve fibers, so their ability to see detail is only approximately 20-40% that of humans.
Tests suggest that dogs' visual acuity may be somewhere between 20/60 and 20/80. This means that your pet can distinguish an object at 20 feet away that you could see at 60 or 80 feet.
However, pets have better vision in dim light than we do. Cats can see with about 85% less light than humans need. Your pet's pupil acts like an aperture for a camera and can dilate to allow superior light capture. Pets have a layer of tissue in the eye called a tapetum lucidum which lies immediately behind or sometimes within the retina. It reflects visible light back through the retina, increasing the light available to the photoreceptors. This improves vision in low-light conditions, but can cause the perceived image to be blurry from the interference of the reflected light. You can see evidence of the tapetum lucidum by shining a light such as a flashlight into your pet's eyes -- the pupil appears to glow.
Pets see fast movement much better than we do. In fact they see movement so well that they may see flickering images on television rather than the continuous image that we can see. Dogs have more rods in the retina than humans - rods are the photoreceptor cells that perceive movement and objects in dim light. Cats are able to track fast moving objects easily, but slow moving objects appear to not be moving.
Dogs and cats have a limited ability to see colors. Although they can see differentiate between some colors (primarily blue and yellow), the colors appear to be pale or faded. It is difficult for most pets to distinguish between orange, yellow and red objects based on color.