Any condition that blocks light from getting to the retina impairs a dog’s vision. Corneal diseases and cataracts fall into
this category. Glaucoma, uveitis, and retinal diseases
are other important causes of blindness in dogs.
Most causes of blindness will not be evident on general observation of the
eye itself. But there are some signs that suggest a dog may not be seeing as
well as before. For example, a visually impaired dog may step high or with
great caution, tread on objects that normally are avoided, bump into furniture,
and carry his nose close to the ground. Dogs who normally catch well may
suddenly start to miss objects thrown to them. The inactivity of older dogs is
often attributed simply to old age, but failing eyesight may also be a
Mange is a skin disease caused by several species of tiny mites, common external parasites found in companion canines. Some mange mites are normal residents of your dog’s skin and hair follicles, while others are not. All mites can cause mild to severe skin infections if they proliferate.
Shining a bright light into the dog’s eye to test for pupil constriction is
not an accurate test for blindness, because the pupil can become smaller from a
light reflex alone. This doesn’t tell you whether the dog is able to form a
One way to test eyesight is to observe the dog in a dark room in which the
furniture has been rearranged. As the dog begins to walk about, see if he moves
with confidence or hesitates and collides with the furniture. Turn on the
lights and repeat the test. A completely blind dog will perform the same way on
both tests. A dog with some sight will show more confidence when the lights are
on. Performance tests such as these give qualitative information about
eyesight, but the degree of impairment can only be determined by veterinary
A diagnosis of blindness or irreversible vision loss is not a catastrophe.
The fact is that most dogs, even those with normal eyesight, do not really see
very well. They rely to a greater extent on their keen senses of hearing and
smell. These senses take over and actually become more acute as eyesight fails.
This makes it relatively easy for visually impaired dogs to get around in areas
they know. However, a blind dog should not be turned loose in unfamiliar
surroundings or he could be injured. In the house, try to avoid moving
furniture, because your dog will have a “mental map” of where things are. When
left outdoors, confine a visually impaired dog to a fenced yard or run. Walking
on a leash is safe exercise. The dog learns to rely on his owner as a
It is important to be aware of impending blindness while the dog is still
able to see. This allows time for retraining in basic commands such as “stop,”
“stay,” and “come.” When the dog actually does go blind, obedience training can
be a lifesaver.
WebMD Veterinary Reference from "Dog Owner's Home Veterinary Handbook"