A closer look: Enlargement or Bulging of the Eye (Buphthalmos and Exophthalmos) in Dogs
Bulging eyes are a common symptom that requires emergency veterinary care because some of the underlying causes lead to permanent vision loss. Urgent care provides the best chance of preserving vision.
Brachycephalic (push-face) dogs are predisposed to bulging eyes.
There are two general conditions under which a dog’s eyes bulge: exophthalmos, and buphthalmos.
Exophthalmos occurs when the eyeball is pushed forward in the socket by something behind it.
Buphthalmos occurs when the eyeball itself becomes enlarged, usually as a result of increased pressure caused by glaucoma.
The severity of this symptom depends on several factors, including:
- Whether one or both eyes are affected
- Whether the eyelid is still capable of covering the eye
- How long the condition is present before treatment
- The underlying cause
In cases where one eye is affected, the cause is likely to be traumatic injury, or something pushing the eyeball out of place such as a tumor or abscess. In cases where both eyes are affected, the cause is typically later stages of glaucoma.
In some cases, the eyes bulge only slightly, allowing the eyelid to continue to cover the eyeball, moistening and protecting it. In more severe cases, the eye bulges past the point that the eyelid can cover it, which allows the eye to dry out and for damage to the surface to occur. These cases are more serious and may result in vision loss if left untreated, particularly if untreated for long periods of time.
Some of the underlying causes of bulging eyes are more severe than others. Many infections, for example, clear up with antibiotics. Myositis typically requires long term medication to control. Some causes, including cancer, may be life threatening.
Testing and diagnosis
Diagnostic tools to identify the cause of bulging eyes include:
- Physical examination
- Ophthalmic examination
- Schirmer test (to determine tear production)
- Fluorescein staining (to detect damage to the surface of the eyeball)
- Tonometry (to test the pressure inside the eyeball)
- Diagnostic imaging, such as ultrasound or X-rays
- Blood work
Referral to a specialist may be necessary.
Treatments depend on the underlying cause, and may include:
- Eye drops or ointments
- Cancer treatment
In brachycephalic (push-face) breeds, the eyes have a naturally bulging shape due to the shallow eye socket. Although this makes these breeds more susceptible to some eye issues, the normal bulginess of the eyes is not a cause for undue concern. Careful monitoring of eye health is particularly important in these dogs.