What the owners of brachycephalic dogs need to know about BOS

The term “brachycephalic ocular syndrome” or “BOS” is one that is only recently coming into common usage in the UK, but it is widely used in other countries to refer to a collective of eye problems that can develop in brachycephalic dogs. It is used much as “brachycephalic obstructive airway syndrome” or BOAS is used to describe a collective of respiratory conditions that can arise in brachycephalic dogs in turn.

Flat-faced dogs are really popular in the UK, but not everyone who falls for the charms of their unique appearances fully understands the implications that come with it. Moderate dogs, being those with only a small degree of flatness to the face, are predisposed to better health and are far less likely to suffer from conformation defects and health problems than those with very flat faces.

Very flat-faced dogs are at higher risk of brachycephalic ocular syndrome or BOS – but what does this mean? Read on to find out.

What is brachycephalic ocular syndrome or BOS?

Brachycephalic ocular syndrome is a collective name for several eye conditions that cause problems specifically in dog breeds with flat faces. The term is also used separately or similarly for such problems in flat-faced cats too.

The exact presentation of brachycephalic ocular syndrome can vary from dog to dog, but the normal collective of issues include tightly drawn and often inverted (pointing inwards) eyelids, which results in trichiasis, or eyelashes rubbing on the eyeball itself, along with the eyes appearing prominent or even protruding due to the particular shallowness of the eye sockets.

Often, there will be a range of other conformation issues and conditions that accompany these problems under the heading of BOS, like abnormal eyelash growth, or even hairs from alongside of the dog’s nasal folds occluding the eyes too, and potential issues with tear production or the tear ducts due to the shape of the eyes.

Issues like high pressure behind the eye and a propensity to injuring the eyes due to their prominence may occur as well.

What dog breeds are predisposed to brachycephalic ocular syndrome?

Flat-faced dog breeds are correctly referred to as being brachycephalic, and any brachycephalic dog breed may therefore be at risk for brachycephalic ocular syndrome.

However, some flat-faced dog breeds tend to have very moderate flat faces, while in other breeds, the norm or fashion is for faces so flat that viewed side-on, the dog may appear to have virtually no nose at all; it is such breeds, and very flat-faced dogs compared to the norm in other brachycephalic breeds, that are predisposed to brachycephalic ocular syndrome.

The condition is far less likely to present in dogs with only moderately flat faces, or from more moderate brachycephalic breeds.

Some of the breeds that are most prone to brachycephalic ocular syndrome are the Pug, English bulldog, French bulldog, and Shih Tzu.

What causes brachycephalic ocular syndrome to develop?

Brachycephalic ocular syndrome comes about as the result of conformation defects of the skull, muzzle and eyes; and these conformation defects are deliberately selectively bred for to achieve the flat-faced appearance that is in such demand in popular brachycephalic dog breeds.

Brachycephalic dogs with more moderate faces and only a slight shortening of the nose are far les likely to suffer from eye problems like BOS.

This means that brachycephalic ocular syndrome is not contagious (although secondary complications of eye problems that result from it like conjunctivitis may be) but is congenital, and is passed on with conformation traits achieved by selective breeding in flat-faced dogs.

How would I know if my dog had brachycephalic ocular syndrome?

If you have a dog with a very flat face, their chances of suffering from eye problems are higher than for both dogs with a normal-length muzzle, and more moderate flat faced dogs.

A very flat face predisposes dogs to the sort of eye problems we’ve mentioned above, and if your dog has very prominent or protruding eyes, their eyelids tilt inwards, their lashes or nasal fur rubs the eyes, or they have other such eye problems, they may have BOS.

Your vet will provide a definitive diagnosis and outline which elements of BOS, if relevant, affect your dog specifically.

Can anything be done to treat brachycephalic ocular syndrome?

In some cases, surgery may be required to correct problems like the angle of the eyelids and so, to stop them rubbing on the eyes, or causing eyelashes to rub on the eyes. Nothing can be done to correct prominent or protruding eyes and so, to lessen the chances of them becoming damaged, and because BOS is a collective of eye defects, conformation issues, and the effects of such issues, the condition may not be fully treatable for every dog.

Remember that even though surgery may improve or correct some BOS issues, those same issue are hereditary and can be passed on to any puppies produced from your dog, and so they should not be used for breeding.