VISION LOSS IN OLDER DOGS
Older dogs, just like older people tend to develop eye problems as they age. The most common eye problems of old dogs are cataracts, glaucoma and nuclear
sclerosis. Blindness can develop from the first two conditions, and from retinal degeneration with age.
Signs that your dog is losing his eyesight are often quite obvious. He might bump into walls or furniture, have trouble locating his food or toys or stop
making eye contact. The signs can also be subtle, a reluctance to jump on or off furniture, expressions of anxiety. He could begin to show aggression
due to anxiety surrounding his loss of vision, in an attempt to keep himself safe.
The American Kennel Club has an excellent article on the
Symptoms and Management of Vision Loss in Senior Dogs.
Let’s take a look at the most common problems senior dogs may incur.
Nuclear sclerosis is a bluing of the lens of the eye caused by fibers growing in the clear lens as a normal part of aging. The bluing may slightly impair
vision, but it does not destroy vision. When you notice a bluish haze over the eye, that is nuclear sclerosis, not a cataract.
While cataracts can affect dogs at a young age, they are most commonly found in older dogs. These cataracts are also known as Senile cataracts. They can
appear for the first time in dogs as young as 6-years of age. Cataracts often go hand-in-hand with diabetes.
Changes begin in the center of the lens and move out to the periphery. As the lens progressively becomes opaque, vision will be lost. Aging cataracts tend
to develop in both eyes, but they may progress at different rates. Cataracts can also result from trauma or infection to the eye and secondary to diabetes
Luckily, cataracts are not painful. You may notice a whitish sheen to the pupil or catch that your dog’s vision is failing. The coloration change needs
to be differentiated from the benign nuclear sclerosis, which your veterinarian can do with an ophthalmoscopic exam.
The only real treatment for cataracts is surgery. The lens can be removed, or it can be broken down by phacoemulsification — a process using ultrasound
to break up the lens. The pieces are then removed from the eye. An artificial lens may be put into place or the eye may be left alone. Surgery is only
attempted if vision has been lost in both eyes. This is a surgery that should be done by a board-certified veterinary ophthalmologist.
Glaucoma occurs when the fluid produced by the eye builds up faster than it can drain. This causes an increase in pressure on the sensitive tissues of
the eye — damaging the optic nerve and the retina. If left untreated, the damage is permanent and may lead to blindness.
Dogs with glaucoma often avoid bright areas, tear excessively and may squint or simply hold their eyes closed.
Primary glaucoma has a genetic basis and is seen in a number of breeds, including Beagles, Cocker Spaniels and Basset Hounds. In these
cases, both eyes will be affected, though not always at the same time. For breeds with a predisposition to glaucoma, having the ocular pressure checked
on every wellness visit is important. Your regular veterinarian can do that on a physical exam with a tonometer. Normal IOP (intraocular pressure)
can range from 10 to 25 mm Hg. Dogs with glaucoma generally have pressures over 25 mm Hg.
Secondary glaucoma occurs after some other eye problem — trauma, a displaced lens or uveitis. In such cases, the original problem
has to be addressed, along with treating glaucoma.
Immediate treatment for glaucoma involves medical therapy. Drugs such as mannitol are used to lower the pressure in the eye. Topical medications will cause
the pupil to constrict, which opens up the angles, so fluid can drain more easily. Because dogs can go blind in hours from glaucoma; always seek veterinary
attention right away if you suspect an eye problem in your pet.
If medical therapy is not effective, there are some surgical procedures that may help with glaucoma. Still, many old dogs with glaucoma will end up blind
in the affected eye(s). If the eye continues to be painful, removal is recommended. You can get a prosthesis or simply have the eyelid sutured shut
Eye Irritants and Other Problems
Senior dogs can get any of the typical canine eye problems as well. Dust, sand or other foreign bodies in the eye, such as plant seeds, can irritate the
conjunctiva or scratch the cornea. You may suddenly notice your dog is blinking a lot, squinting his eye, holding his eye shut or tearing. Flush his
eye with artificial tears but always call your veterinarian. Eye problems can go from minor to vision-threatening in a very short time.
VISION LOSS IN OLDER CATS
Looking for Trouble
The signs that your cat has become visually impaired may be quite obvious. The animal may, for example, start bumping into furniture, trip as it climbs
up or down a flight of stairs, or appear to have trouble finding its litter box or food bowl. In some cases, however, the behavioral signs that something
is going wrong with your cat’s vision may be too subtle to detect, says Dr. Thomas Kern.
Therefore, he advises, you should have your cat’s eyes thoroughly examined periodically by your veterinarian. In addition, you should routinely monitor
the health of your animal’s eyes.
“Look for changes in the color of the iris, for example, or see if the eye seems to be cloudy or if the cat’s two pupils appear to differ from one another,”
he advises. “Such changes can reveal a problem before it progresses to an irreversible stage.”
Healthy feline eyes will be bright and clear, the pupils will be of equal size, and the cat will not be squinting with either eye. There will be little
or no tearing in the corners of the eye; the tissue lining the eyelid will be a healthy pink; and the membrane of the third eyelid will not protrude.
“If you spot anything unusual,” Dr. Kern advises, “get it checked out promptly by your veterinarian.” Early treatment, he points out, may prevent or delay
the onset of blindness.
Frequent DisordersCats are subject to a host of diseases that can cause permanent damage to any or all of the eye’s components. These disorders include
cataracts, in which the lens gradually clouds up—often impenetrably—and prevents light from entering the eye; glaucoma, a condition marked by excessive fluid pressure within the eyeball that can cause it to harden; progressive retinal atrophy,
in which the retinal tissue degenerates and loses its ability to function properly; and a variety of tumors—either malignant or benign—that
develop within the eye or adjacent to it.
For comprehensive information on feline health issues, we recommend Cornell University College of Veterinary Medicine’s – Cornell Feline Health Center
#3 in our Series, Hearing Loss in Senior Pets coming your way on November 26, 2018