What is Exophthalmos?
Exophthalmos is the term used for a forward deviation of the eye out of the boney orbit. The most common causes of exophthalmos will affect one rather than both eyes, although there are a few conditions which can affect both eyes. There are many structures near the eye and orbit including muscles, salivary glands, tooth roots, bone and nerves, and abnormalities or inflammation of these tissues can affect the positioning of an otherwise normal appearing eye.
Small animals with exophthalmos will present with a forward deviation of the eye. This condition can commonly be confused with proptosis, or a sudden forward displacement of the globe with an entrapment of
the eyelids behind the eye. Pets with exophthalmos most often have a slow progression of clinical signs and change in the appearance of the eye and affected side of the face. Small animals with exophthalmos may or may not be painful around their face and mouth depending on the underlying cause. There may be inflammation of the conjunctiva and other tissues surrounding the eye and orbit and the third eyelid may be raised. If the condition is progressed, a pet may not be able to fully blink their eyelids leading to corneal ulceration and irritation. Depending on the cause of exophthalmos, animals may demonstrate systemic signs of illness such as decreased appetite, fever and lethargy.
What Are Causes of Exophthalmos?
Possible causes for exophthalmos in dogs and cats include infection or inflammation behind the eye, inflammation of the salivary glands or muscles, and tumors of the orbit. Small animals can develop abscesses behind the eye due to foreign material, trauma or bite wounds which introduce bacteria under the skin, or advanced dental disease. Certain infections can also travel to this area through the blood stream, causing inflammation behind the eye. Inflammation of the muscles surrounding the eye (myositis) can occur
with certain infectious diseases and can also be due to an inherited condition (extraocular muscle myositis or masticatory muscle myositis). Many of these conditions will cause discomfort to a pet when trying to eat or when the affected side of their face is touched. Cancer of the tissues surrounding the eye, nasal sinuses and mouth can also lead to an abnormal position of the eye.
How Can The Cause Be Identified?
Based on an animal’s history of progression, clinical symptoms, any known traumatic event and other history,
a number of tests may be recommended. It can be important to identify the underlying cause of exophthalmos to provide the best medical care and to assess prognosis for the pet. Systemic blood work and blood or urine fungal testing may be recommended. Abdominal ultrasound and chest x-rays are useful if a cancerous cause or fungal disease is suspected. Advanced diagnostic imaging such as a CT scan is oftentimes advised to better understand the cause of exophthalmos, but also to evaluate the extent or size of abnormal tissue.
What Are The Treatments For Exophthalmos?
Oral antibiotics and anti-inflammatory medications are commonly used for treating orbital abscesses and inflammatory conditions. If salivary gland swelling or an abscess is considered likely, surgical drainage and sampling of fluid for analysis can help in diagnosis and guide the doctor in forming the appropriate treatment plan. If diagnosed, fungal diseases require oral antifungal therapy and close monitoring for response to therapy. Topical lubricants are used to protect the eye from drying due to decreased blinking. Additional treatment for a corneal ulcer may also be needed. If a tumor is suspected, consultation with an oncologist is most often recommended to discuss different treatment options or pain management after diagnosis. Feeding soft foods is recommended if a patient shows discomfort when eating and warm compresses can provide additional comfort.
Pets with many inflammatory conditions can regain normal comfort and position of the eye long term. It is important that any animal with exophthalmos receive an eye exam to determine the most likely cause and best course of action.
Exophthalmos of the left eye of a dog cause by a tumor, known as an osteosarcoma, of the jaw (mandible).