Anatomy of the Dog & Cat Eye
The eyes of dogs and cats work primarily in the same manner as a human eye. The eyes are organs that function much like a camera for the brain. The image dogs and cats see passes through the lens and is placed on the retina, then sent to the brain for processing. There are, however, some differences in the eyes of cats and dogs when compared to each other's and those of humans.
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Dog's Eye Features
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Dog eyes allow for excellent capture of movement. A dog's eye allows for vision. The eye is composed of a lens, cornea, iris, retina and optical nerve, much like a human's. The dog's eye is structured slightly differently, giving the canine a different range of vision and sight abilities. The retina is designed to be sensitive to low light, allowing the dog to see better in low-light circumstances.
Dogs also have a third eyelid, which helps to keep the eye clean of foreign materials. Often seen in the corner of the eye, this membrane is also visible when a dog is starting to close his eyes to sleep or when he is just waking. The upper eyelids conceal a gland that produces tears, and there are ducts in both the upper and lower eyelid to keep the eyes from being overcome with tears.
Cat's Eye Features
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The slit pupil is seen here; it can get even smaller. Cats have exceptional vision. Their eyes dilate to see more of a landscape, and are expert at capturing movement, like a dog. While there is a blind spot directly under their chin, other areas of sight, including peripheral, are extraordinary, especially when compared to humans.
The cat's eye has a distinct pupil. Sometimes seen as a simple "slit" in the eye, the cat's eye has been referenced for stones and jewels. The pupil is quite adept at allowing the cat's preferred vision at any given time. While in its "slit" phase, the cat can see very well in lower light, but may have trouble focusing properly. In its round phase, the pupil lets in a great deal of light, but with the possibility of interrupting the cat's depth of field.
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General Anatomy
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The front of the eye is covered by the cornea, which protects the lens and iris. Most of the eye consists of the vitreous body, or a gel-like substance behind the cornea, lens and iris. The retina lies at the back of the eye. Attaching the eye to the brain is the optic nerve, through which the eye sends signals to the brain for decoding the seen image.
Tapetum
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Dogs and cats, along with some other animals, also have a reflective tapetum. This membrane reflects the light passing through at night. The tapetum is what allows us to see the eyes of many animals at night with the light of our cars, flashlights or other light sources.
The tapetum in dogs and cats, along with other specialized features of the retina, helps the animal in low-light conditions. Many cats are nocturnal, and as such they do a majority of their hunting at night. Dogs in the wild often hunt in lower-light conditions, such as dawn and dusk.
Warning
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Both cats and dogs are prone to many diseases affecting the eye. Cats are prone to infections of the cornea, or the clear outer layer of the eye. With the wide variety of dog breeds and eye types, dogs have many possible diseases. Cherry eye, blepharitis and conjunctivitis are common.
Because they are prone to disease, regularly examining your dog's or cat's eyes is advisable. If you notice any changes in your pet's eyes, consult a veterinarian with your findings. Early diagnosis of problems can often alleviate the pain and suffering your pet may go through without treatment.
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References
Resources
- Photo Credit cat eye image by Cesar Andrade from Fotolia.com dog eyes image by Vaidas Bucys from Fotolia.com cat eyes image by Gareau Enterprises from Fotolia.com
