If you have ever seen a cross-eyed dog, or a dog whose eyes appear to be looking in two different directions at once, the correct term for this is strabismus-and this condition is more common in certain breeds and types of dogs than others.
While the condition is not usually painful and doesn’t normally actually affect the dog’s vision acuity, it does change the way that they see the world, and affect factors such as their depth perception, ability to judge distances, and focus accurately. In some cases, the condition can be corrected-particularly if it occurs as the result of an injury rather than due to a hereditary deformity-and the sooner that the condition is identified, diagnosed and if necessary, treated, the more successful corrective treatment is likely to be.
In this article, we will look at strabismus in dogs in more detail, including what causes it, what sort of dogs are at risk of the condition, how to identify it, and what can be done about it. Read on to learn more.
Strabismus is the clinical term for being cross eyed-and this may affect either both eyes, or just one of them. An eye or both eyes that point inwards towards the nose is what we normally mean when we use the term cross eyed or strabismus, and its full name is convergent strabismus-but if one or both eyes instead point outwards instead of inwards, this is known as divergent strabismus.
The term itself refers to the eyeball being in an unusual position, and/or both eyes moving independently or not focusing in the same way together, if there is one normal eye and one cross eye.
In eyes with strabismus, the physical cause may be that the muscles that affix the eyeball in place and that control movement may be uneven, with one side having a longer muscle than the other-or one muscle being too weak to control direction and focus properly.
Strabismus in dogs is usually hereditary, and occurs in dogs that have inherited a congenital weakness or flaw that affects the normal structure, development and behaviour of the eyes. If one or both of any given dog’s parents themselves had strabismus, that dog will have a higher chance of having the condition themselves-although not all dogs with hereditary strabismus will have parents that are obviously cross-eyed.
Additionally, injuries that affect the eyes or brain can lead to strabismus developing, and a range of diseases and degenerative conditions that affect the eyes or brain and specifically the nerves or muscles can also potentially cause strabismus.
Because injuries and degenerative conditions can cause strabismus, theoretically any dog can develop the condition-but much more commonly, dogs will inherit the condition as a congenital flaw. Certain dog breeds are more prone to strabismus than others, including the pug and the Boston terrier, and dogs that have strabismus themselves or that have close relatives with the condition should not be bred from, as this increases the risk of further generations inheriting the problem too.
Strabismus can be very obvious or very subtle, so it is wise to familiarise yourself with the normal appearance of your dog’s eyes, to look out for potential symptoms. The condition may affect one or both eyes, and may cause the affected eye or eyes to either point in towards the nose, or out towards the side of the face.
This will make the dog’s eyes look uneven or poorly matched, and as if the eyes are either looking straight down their nose as if they have spotted something on the end of their nose, or looking out in two different directions at once.
Affected dogs will usually have normal vision acuity, but they are apt to find it hard to focus on individual objects and so may have problems looking right at things, as well as issues with depth perception and spatial awareness, particularly in poor lighting.
In cases of congenital hereditary strabismus, the condition is largely cosmetic and may make the dog look a little odd, but otherwise have little to no effect on them, because they do not have any frame of reference for seeing the world differently. For this reason, surgical correction or other forms of treatment are not usually indicated in congenital presentations of the disorder, because there is no real reason to do so.
However, if strabismus develops later on in life, this is more likely to be the result of an injury or degenerative health condition, which will require investigation by your vet. Treatment of the underlying problem or issue that caused the condition will often correct the strabismus on its own, but in some cases, surgical correction may be possible too, although this is relatively unusual and rarely performed without a clear benefit from doing so.