HEALTH MATTERS: Making sense of your pets' senses

Our pets perceive the world around us in much the same way we do. They have the same five senses of sight, hearing, touch, smell and taste.

Pet owners may seek veterinary care when one or more of these senses become either over- or under-stimulated. For example, your pet may start to bump into the coffee table or doorway with a sudden or gradual onset of vision loss. He or she may act lethargic or have an altered sleep cycle with a condition affecting the hearing. An altered touch perception may manifest itself as a cry or yelp when picked up or petted. It is important to recognize what are normal senses for your pet so when there is a problem, proper care can be administered.

Vision
The typical domestic dog has 20/75 vision, which is comparable to the typical 90-year-old human. While different from humans, dogs are far from blind. Stemming from their days when survival was the name of the game, a dog’s ability to see movement in dim light is magnificent. Because of the biological makeup of a dog’s eye, their ability to see color is vastly different from us because their retinas have fewer cones, which detect color, but more rods which detect light, than humans. This means that dogs can distinguish color, usually in the blue and violet ranges, but their true ability lies in their skill to see well when light levels are low.

The breed and, therefore, the anatomic makeup also plays a role in your pets sense of vision. For example, a greyhound, with its long nose and closely set eyes, sees the world differently from a pug that has a short face and wide-set eyes. It would be abnormal to expect a pug to put a mark on a rabbit unless it was right under its nose.

Loss of vision is commonly caused by hereditary or acquired diseases. For example, a hereditary condition called progressive retinal atrophy causes gradual blindness and is seen primarily in young to middle-age poodles. Acquired diseases such as diabetes can lead to cataract related blindness. Tick-borne infections also can cause vision loss.

It’s important to understand that if your dog becomes blind, don’t despair. This is not a reason to euthanize your pet. It will rely on its other senses to compensate.

Hearing
The next sense is hearing. Although hearing skills differ between the breeds, in general, dogs can perceive sounds twice as high as humans and can hear a sound clearly 10 times farther away than a human. This is especially interesting to remember when your dog seems not to hear a thing you say. You may then start thinking of either hereditary or acquired causes for hearing loss. Hereditary hearing loss is seen commonly in Dalmatian dogs and in cats with white coats and blue eyes.

If you suspect that your pet may be deaf, a test called a Brainstem Evoked Auditory Response, or BAER can be performed. This is a type of a hearing test usually performed in young pets to try to eliminate the deaf pets from the breeding stock, but can be performed at any age. It’s a painless test and does not require anesthesia. Acquired causes for hearing loss may include ear infections, drug toxicity from chronic application of ear medications, noise trauma and presbycusis (age-related hearing loss). Always approach a deaf pet slowly so it is not startled. Use the other sense, touch, to let it know that you are near.

Touch
The third sense, touch, is an important sense for the pet owner to understand. When this sense is at its extreme, your pet can feel pain. Animals do feel pain in the same way that we do. What is different is how they react to the pain. It’s a survival instinct to hide their pain from a prey animal, so a pet in pain may hide or sleep perhaps under the bed. Obvious pain signals may include vocalizing, panting, or abnormal posturing.

Pain in your pet may be caused by any number of stimuli from a surgical procedure to age related conditions like arthritis. There are now state-of-the-art pain-management modalities for your pet.

Smell and taste
The last two senses are smell and taste. Animals generally can catch a whiff of something 100 times less concentrated than what we can smell. To put this in more understandable terms, while humans can smell bread baking, a dog can smell a week-old crumb left under the refrigerator.

From a clinical perspective, pets often are victims of their own design. They eat and sniff things such as dirt and other pets’ rear ends, for example, which puts them at higher risk for infections and illness. One the other hand, scientists have used pets keen sense of smell in a positive way by using them to detect skin cancer in people.

Dr. Howard Small is an East County veterinarian at The Animal Hospital at Lakewood Ranch, 10930 S.R. 70 E. For more, call 751-0101.

Click here to view the December 2011 Health Matters special section.