Dog’s eyes

Dog’s eyes

“Eyes are the window to the soul,” is an old English proverb that, according to scientists, also holds true for our dogs.

Your dog uses his eyes to communicate with you. He tells you he’s ready for a walk, wants to play and is happy.

Your dog’s eyes are one of his most precious and most complex organs. And because they are so important to his wellbeing throughout his life, you will want to do what you can to support and maintain his healthy eye function.

Anatomy of a Dog’s Eye

A diagram of a dog’s eye

• Although his eyes may look very similar to human eyes, the eyes of dogs differ in a number of ways.
•  Dogs have very large pupils to see better in dim light conditions.
• Dogs have more rods than cones. Rods are used for detecting movement rather than colour and details.
• Long nosed dogs have a “visual streak” that allows them to focus sharply at a distance and gives them great peripheral vision. That’s why they can see a squirrel in the faraway tree and are so good at searching for a toy or ball.
• Short nosed dogs have high density vision cells (instead of a visual streak) that gains them an advantage in reading your facial expressions.
• Dogs have a third eyelid (nictitating membrane) that works as a thin shutter to protect the eyeball.

The uniqueness of dog’s eyes, in the way that they work, seem to align them with what they were bred to do.

How dogs see the world

To understand your dog’s sense of vision, you need to know how your dog’s view of the world differs from your own.

• The average dog’s visual acuity is sometimes compared to a human’s at sunset. There are exceptions, but most dogs see forms rather than distinct images or features.
• Colour: Human eyes have three types of cones that can identify combinations of red, blue and green. Dogs have only two types of cones and can only discern blue and yellow. This limited colour perception is called dichromatic vision.
• Dogs especially rely on their keen sense of smell to “read” their world, so for them, vision is secondary. I have often watched how my dogs, when searching for a ball, are about to run past it and then will suddenly turn directly to it and retrieve it. They smelt the ball and are therefore able to retrieve it quickly.

Human vs dog vision

Dogs have evolved in a natural world where darkness offers advantages – and sometimes the key to survival. Wild dogs escape to their dens to rest in safety and away from the glaring sun.

In your home there should be an area where your pet can retreat into darkness from the continuous glow and glare of artificial, fluorescent light.

If they spend a lot of time outdoors, they should have a tree or shady spot to retreat to.

ASPCA eye health tips

1. Sit facing your dog and look into his eyes. They should be clear and bright and the area around the eyeball, the sclera, white. If there is cloudiness, change in eye colour or a yellow-tinged sclera, unequal pupil sizes, or a visible third eyelid, check with your vet.
2. Carefully roll down his lower eyelid with your thumb until you can see the lining. It should be pink, not red or white.
3. Use a damp cotton ball to remove dirt and discharge, wiping outwards from the corner of the eye.
4. Keep hair trimmed around your pet’s eyes. Use scissors with rounded tips.
5. Avoid using irritating soaps, shampoos, and sprays or lotions.
6. Watch your dog’s behaviour. Does he frequently paw or rub his eyes? Does he often squint?
7. When you drive with your pet, make sure that his head stays inside the car. Dogs do not blink as often as people. On a hot day the wind can dry your dog’s eyes very quickly causing, irritation, infection, or injury when a bug or debris hits his eye.
8. Make sure that at the regular pet checkups your vet checks his eyes at each visit.

What happens to the eyes with Age?

As dogs age their owners notice a clouding of the lens. Often seen in dogs over the age of 6, nuclear sclerosis usually develops in both eyes and can be alarming for pet owners if they don’t know it’s a normal and painless process of old age.

The cell layer used for night vision becomes thinner and the dog becomes hesitant to go outside at night. That could be the reason.

Some dogs become more light- sensitive as they age. The muscle in the iris that constricts the pupil weakens with age, making bright light less tolerable. This too is part of aging in pets.

Any change in your dog’s eyes that appears suddenly or anything that you find concerning is a good reason to see your veterinarian.