Many pet owners have wondered if their dog or cat sees the world the same way that they do. And thanks to advances in science and technology, we now know that their world looks slightly fuzzier, in duller shades of blue, yellow and green, than ours. However, cats and dogs have other eyesight advantages. They can see significantly better in low-light conditions and quickly spot very slight movements over a wider field.
Dogs and cats don’t rely on their eyesight to the same extent we do. For them, smell and hearing are the first and second most important special senses, with vision coming in third. When dogs and cats lose their vision, especially if the loss is gradual, they adapt amazingly well to their new normal. In fact, dog and cat owners may not recognize a pet’s blindness until the pet stumbles into furniture or other objects that are out of place.
So, how can pet owners tell if their pet is experiencing vision loss?
Looking for signs of trouble
Signs that your cat or dog has become visually impaired can be quite obvious. Your pet may trip going up or down stairs, hesitate to jump up or down, bump into furniture or have trouble finding the food bowl or litter box. If eyesight issues are caused by disease or infection, you may notice changes in your pet’s eyes. Your cat or dog may squint or rub one or both eyes. Or you may notice redness, discharge, cloudiness or color changes.
In many cases, however, the changes in behavior that indicate something’s amiss are too subtle for pet owners to detect.
Pet owners can watch for signs or symptoms of eye-related diseases and conditions. If you notice your cat or dog is experiencing any of the noted symptoms (see box), contact your veterinarian for an appointment.
How a veterinarian may evaluate your pet’s vision
From a preventive health care perspective, regular physical exams every six to 12 months give your veterinarian an opportunity to evaluate your pet’s eyes and vision. Depending on what your veterinarian observes during the exam, he or she may perform one or more tests to evaluate your pet’s eyesight.
The menace reflex test uses a sudden, and potentially threatening, hand motion directed toward one eye of the pet while the other eye is covered. A normal response is a blink. It’s important to avoid creating air currents during hand motions because they’ll also trigger blinking, even in a blind pet.
The tracking response test involves dropping a cotton ball through the dog’s or cat’s field of vision, one eye at a time. The eye not being tested will be covered. Your veterinarian will watch to see if your pet’s eye follows the cotton ball as it drops.
Pupillary response is evaluated by shining a bright light into the eye and assessing pupil constriction. The pupils of pets with normal vision should get smaller or narrow to a slit in the case of cats. However, pupil constriction can still occur in a blind pet if vision loss isn’t caused by disease or damage to the retina or optic nerve.
The dazzle reflex test involves shining a bright, focused light suddenly into the eye. Pets with normal vision will blink, squint or turn their heads away. But a blind pet will continue to look ahead since it can’t see the light.
The interior structures of the eye can be evaluated during an eye exam in pets, just as they are in people. The pupils are dilated, the exam room darkened and an ophthalmoscope with a light source is used to examine eye structures including the lens, iris, retina, optic disc, blood vessels of the retina and tapetum lucidum, a tissue layer beneath the retina that reflects incoming light. Masses, opaque or cloudy areas and other abnormalities can often be found during that part of the eye exam.
Your veterinarian may also recommend and/or perform additional tests to evaluate your pet’s ability to produce tears (known as the Schirmer tear test); detect damage to the cornea, the transparent outermost layer on the very front of the eyeball; and check the pressure inside the eyeball (known as tonometry). Results from these tests can be used to detect underlying eye health concerns, such as “dry eye,” injury to or ulceration of the cornea, and glaucoma, respectively.
Set your sight on the bottom line
Many conditions affecting your pet’s eyes are treatable if found in the early stages. Even glaucoma, which can’t be cured, can be managed and its associated blindness delayed with proper treatment.
And if your dog or cat does become blind? They can actually live a nearly normal, happy life.
If you have any questions about your pet’s eyes, vision or other body systems, talk with your veterinarian. After you, your veterinary health care team is your pet’s biggest health advocate.
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