Pet Retrobulbar Masses
A retrobulbar mass is a space occupying lesion occurring within the orbit (eye socket) usually located behind the eye.
What are the clinical signs of a retrobulbar mass?
Classic clinical signs associated with a retrobulbar mass include extrusion of the globe (exophthalmia), dislocation of the globe, redness, and protrusion of the third eyelid. Some cases are quite painful, presenting as avoidance of touching, inability to open the jaws, lethargy, vocalization, and inappetence. Periorbital swelling and discharge can be present in some patients. Blindness of the affected eye may or may not be present.
What are the causes of retrobulbar mass?
The most common causes of a retrobulbar mass are abscess or cellulitis, sialocele (cystic structure of the salivary gland), and cancer.
Abscess/cellulitis usually develops rapidly, is usually quite painful, and typically in young large breed dogs. Causes of the retrobulbar infection trauma, hematogenous emboli, or tooth root abscess. Sialoceles develop slowly, are not painful, and are most common in Boston terriers.
Retrobulbar cancer typically develops slowly, may or not be painful, and in older patients. Cancer is the primary retrobulbar mass in cats and older dogs. In dogs, the cancer tends to be benign and originates from tissue within the orbit. In cats, the cancer is typically malignant, arising from non-orbital tissue that invades the orbit
How is a retrobulbar mass diagnosed?
If a retrobulbar mass is suspected, imaging of the orbit is utilized to confirm the presence and determine the extent of the mass. While not sufficiently sensitive to diagnose all instances of an orbital mass, an ocular ultrasound can identify the presence of some orbital masses and aid in the collection of samples from the mass for the culture of infectious organisms or identifying the type of cancer. More advanced imaging, such as a CT scan or MRI, is more accurate to determine the presence and location of a retrobulbar mass and will reveal if the mass is restricted to the orbit, if a tooth root abscess is present, if the mass is an extension of non-orbital cancer into the orbit, or if a cancerous mass has spread from the orbit into surrounding tissue, including the brain.
What are the treatments for a retrobulbar mass?
The treatment of a retrobulbar mass varies depending on the type of mass, how extensive the mass is, the origination of the mass, and the health of the globe. A retrobulbar abscess/cellulitis is typically treated by establishing a draining tract from the root of the mouth to the orbit under anesthesia in conjunction with aggressive systemic antibiotics and anti-inflammatories. Retrobulbar sialoceles can be periodically drained, injected with a sclerotic agent to promote scarring, or removed surgically. Cancer that is involving the orbit may be removed surgically either by an orbitotomy that saves the eye or an externeration in which all the tissue within the orbit, including the eye, is removed, followed by chemotherapy or radiation therapy if required. If the cancer is too extensive, then treatment with chemotherapy or radiation may be the only treatment option.