What do dogs see? Dr Amanda Nott reports from a recent Ophthalmology conference run by the Centre for Veterinary Education at Sydney University. Keynote speakers were a many of the leading veterinary ophthalmologists from around Australia.
Many people have often wondered what their dog is able to see – especially in regards to colour. During evolution dogs developed different abilities to help them survive compared to humans. They were not foragers like human ancestors, but rather required the ability to detect and follow prey during the day and night.
Dogs have better ability to see in low light compared to people, but are not as well equipped for this as cats. This is achieved by having many light receptors in their eyes (rods) as well as a reflective layer at the back of their eyes. This reflective layer bounces light back to the receptors for even more chance of detection.
Dogs have fewer types of colour receptors (“cones”) in their eyes compared to humans. The cones are most sensitive to violet and yellow-green light, making their colour spectrum different to people. They are thought to have very similar colour vision to people that have red-green colour blindness. So to your dog, red-orange appears as yellow and green-blue looks similar to grey.
Hence “roses are grey, violets are grey”.
Most dogs are neither near or far-sighted, but find distant objects are sharply focused. Some breeds are more near-sighted (i.e. Rottweilers, Miniature Schnauzers and Toy Poodles) while others are more far-sighted (i.e. Australian Shepherds and Alaskan Malamutes). Most dogs are not able to clearly focus on objects 30-55cm in front of their eyes, compared to many children who can clearly focus on objects about 7cm in front of their eyes. Dogs cannot focus on as small objects as a human with 20/20 vision could at a distance of 6 meters – a human ophthalmologist would class a dog as having about 20/75 vision.
Field of view
The filed of view refers to how wide or narrow the visual field of an animal is. Predator animals usually have narrower fields of view compared to prey animals. Dogs have developed as predators and have a field of view of about 240 degrees compared to humans who have a field of view of 180-200 degrees. Horses (a prey species) have a field of view of 357 degrees! They have a small blind spot right behind their tail and an ever smaller one right in front of their nose. The field of view would vary slightly between breeds as there is some variation in how long the nose is and how far apart the eyes are (i.e. a pug compared to a collie).
Dogs are more stimulated by moving objects… this is why a dog will often “ignore” a stationary object, but start chasing it as soon as it moves. There was a study of police dogs that found that the dogs could detect particular moving objects at 810-900m but when these objects were stationary they only detected them at 585m.
So the world appears quite differently to your furry friend – although just as much fun (possibly even more!).
The team at Inner South Veterinary Centre are here to help if you have any problems with your dog’s or cat’s eyes. Whether you are worried about vision, sore eyes, itchy eyes, runny eyes, red eyes, blue eyes or anything else, please call our clinic today for an appointment with one of our veterinarians.