How do animals see?
Animals and humans see by the same mechanism. Imagine that the eye is like a camera. In a camera, light comes in and is focused by the lens onto the film at the back of the camera. In the eye this is similar, except the film at the back of the camera is called the retina. The retina then converts the image into a signal which travels via the optic nerves to the brain. The brain then interprets the signal. Any problem along this pathway can therefore cause blindness.
Signs of Blindness in Animals
The ageing process will reduce focusing ability but will not, in itself, cause blindness. Animals that have decreased vision are more clumsy than normal, may have temperament changes and bump into things. In some cases your pet can be extremely good at disguising blindness, especially if kept in a familiar environment. Some animals which are clinically totally blind, cope remarkably well in their home. This is especially so in cases where the blindness gradually develops, such as with many retinal diseases. Often it is only when the owners take their pet to unfamiliar places that they realise the true extent of their pet’s vision loss.
Causes of Blindness in cats and dogs
There are many causes of vision loss in cats and dogs. In cats some of the more common causes include retinal diseases such as retinal detachment, glaucoma and abnormalities in the brain. In dogs retinal diseases are a much more common cause of blindness. Diseases such as progressive retinal atrophy, glaucoma, sudden acquired retinal degeneration syndrome (SARDS), and cataracts are common causes. Brain diseases are a less common cause of blindness.
The first thing to do is to consult an eye specialist if you are confronted with a blind pet. It may be relatively easy for us to see what the problem is. If we can’t immediately diagnose the problem, we may need to perform further tests. These may include tests of the retina (electroretinogram or ultrasound), and possibly more involved tests such as CAT scan, MRI or a CSF tap. These will be discussed if needed. An accurate diagnosis is important as appropriate medications may restore vision.
What happens in my animal is permanently blind?
Unfortunately, in some cases, blindness is irreversible. Dogs and cats that are permanently blind can still have a very good quality of life. There are ways in which you can help your pet cope with blindness. These include not moving things around the house, removing sharp or pointed objects (e.g. branches of trees) , using scent (such as eucalyptus oil) on the base of chairs or obstacles so that the animal can smell it and in some cases keeping the house well lit. Most blind dogs still enjoy going for walks, particularly on familiar routes.
Avoid access to swimming pools, steep drops and roads. Remember your pet may not see other animals in their environment and so may be apprehensive in their presence. Placing a bell on the collar of a second pet in the household may reassure the blind pet. There are multiple products on the market that are available to help avoid your vision-impaired pet from bumping in to items around them. We can make recommendations on what product is most appropriate for your pet on assessing their degree of vision loss. Familiar noises around the home will also assist with orientation. Remember, as dogs age, hearing often diminishes.