Below is an article on dogs vision by PetMD

How Do Dogs See the World? 

Written by:Mindy Joyner, DVMPUBLISHED: OCTOBER 29, 2021FacebookTwitterPinterest

You may be under the assumption that because dogs can hear better than us, they can probably see better than us, too. But that’s not necessarily the case.

Let’s take a look at the anatomy of a dogs eye and how a dog’s eyesight compares to ours—from seeing colors to side vision and seeing in the dark.

Dog Eye Anatomy

The anatomy of a dog’s eye is very similar to that of a human eye. Dogs have an upper and lower eyelid, the same as people.

There are many other similarities, including:

• 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.

What Eye Colors Can a Dog Have?

The iris, or colored part of a dog’s eye, can be brown, blue, golden, or hazel. Brown is the dominant color for most dogs. Dogs can have two different-colored eyes, which most often occurs in dogs with a merle coat pattern, or in certain breeds such as Huskies or Australian Shepherds.

If a dog has light-colored (blue) eyes, it does not mean that they will have vision problems, blindness, or any other health concerns. The iris pigmentation can vary depending on breed, color of the face, and genetics.

How Good Is Dog Vision?

How does a dog’s vision compare to ours? There’s no simple answer, since dogs have worse eyesight in some respects, but better eyesight in other areas. Here’s how a dog’s eyesight stacks up when it comes to visual acuity, peripheral vision, detecting movement, seeing colors, and seeing in the dark.

Do Dogs Have 20/20 Eyesight?  

Dogs cannot see objects as well as humans. Normal human vision is 20/20. Most dogs have a visual acuity of 20/75, meaning a dog has to be 20 feet away to see an object as well as a person can see at 75 feet away. Labrador Retrievers, which are a breed commonly used as seeing-eye dogs for humans, have better eyesight that is closer to 20/20.

Are Dogs Near-Sighted or Far-Sighted?

A dog’s vision is blurry. If a dog were a human, they would be considered near-sighted and would need glasses to see objects farther away, like the board in the front of the classroom or a road sign.

How Well Can Dogs See Moving Objects?

Dogs have more rods in the retina than humans do. Rods are sensitive to shape, movement, and dim light. Dogs can see moving objects much better than stationary objects, and they have 10-20 times greater motion sensitivity than humans.

Dogs can pick up on small changes in body posture and movement as a result. This is one reason why dogs can be trained with silent cues using hand gestures.

Can Dogs See in the Dark?

Dogs have several anatomical advantages that allow them to see better in the dark than we can:

• More rods in their retina, which function better in dim light
• Larger pupils that allow more light into the eye
• A lens that is closer to the retina, making the image brighter
• The tapetum lucidum, which reflects light, allowing for better night vision

Can Dogs See Color?

Dogs can see color, but only in shades of blue and yellow. Because dogs can only see two colors, they have dichromatic vision. They can also see shades of gray. Colors such as red, orange, and green are out of a dog’s color spectrum, so these colors are not visible to dogs. This is why hunters can wear orange to be visible to other hunters but not to animals. People have what’s called trichromatic vision, which means we can see a lot more colors than dogs.

Do Dogs Have Side Vision?

A dog’s eyes are spaced slightly farther apart than ours, at a 20-degree angle. This greater angle increases the field of view and therefore a dog’s peripheral (side) vision.

How Do You Check a Dog’s Vision?

Dogs can’t read an eyechart, nor do they need to be able to read or write. Because they have less need for good eyesight, known as visual acuity, checking a dog’s vision is very basic.

If a dog can walk into a room through the door or navigate an obstacle course in an exam room in bright and dim light, they are said to have decent vision. Dog eye specialists, or veterinary ophthalmologists, can perform dog eye exams, check their vision, and perform surgery to help dogs see better, such as cataract surgery.