Orbital diseases can be presumptively diagnosed based on history, signalment, and ocular and physical examinations. Abscesses,
parasitic infections, cysts, and varices are more common in younger dogs, while neoplasms are more common in older dogs. Abscesses
are often associated with fever and pain.
All dogs with suspected retrobulbar disease should have a thorough oral examination, especially in the space behind the last
premolar tooth (Figure 5). Tooth root abscesses of the upper fourth premolar in dogs rarely cause retrobulbar disease. These abscesses generally drain
anteriorly to the orbit at the level of the nasolacrimal sac. If a swelling is noted behind the last premolar, an aspirate
of the retrobulbar area may be obtained by placing a 22- or 20-ga needle into the swelling and directing it behind the eye
with the aid of ocular ultrasonography.22
5. Swelling behind the fourth premolar in a poodle.
In most cases, ultrasonography of the retrobulbar area should be performed early in the diagnostic work-up (Figure 6).22 This will help differentiate between fluid-filled structures and solid masses. If purulent material is obtained by means
of an ultrasound-guided aspirate, then a retrobulbar abscess can be diagnosed, and culture and sensitivity testing of the
material should be performed. If no diagnostic material is obtained, further retrobulbar imaging can be performed.
6. An ultrasonogram of a dog’s eye. The dog had clinical exophthalmos. The ultrasonogram shows a heterogeneous mass in the
medial aspect of the retrobulbar space. An exploratory surgery demonstrated this to be a neoplasm.
Computed tomography (CT) or magnetic resonance imaging (MRI) are other methods commonly used to obtain images of the retrobulbar
area (Figure 7).23-25 The method chosen depends on the availability of equipment, owner preference, and index of suspicion of the disease involved.
Plain radiographs of the skull are not useful in orbital disease unless bony involvement or metallic foreign material is present.
7. An MRI of a dog with a retrobulbar mass (arrow). Note the soft tissue swelling around the globe and the apparent smaller
TREATMENT AND PROGNOSIS
Treatment of orbital disease varies depending on the diagnosis. The prognosis for saving vision in the affected eye depends
on the cause.
If an abscess is diagnosed, orbital drainage and systemic antibiotic therapy is indicated.1 To establish drainage, make an incision with a surgical blade into the mucous membrane over the swollen area behind the
fourth premolar tooth. Carefully introduce closed hemostats into this incision, and bluntly dissect and explore for an abscess
8. When draining a retrobulbar abscess, the approach is from behind the fourth premolar tooth. An incision is made through
the mucous membrane, and hemostats are used to bluntly dissect the soft tissue on the floor of the orbit. Ideally, saliva
or purulent material can be removed via this route.
If purulent material is obtained, allow it to drain into the mouth, using caution not to let it go down the throat. A sample
should be examined cytologically to determine if it is a bacterial or fungal infection and then submitted for culture and
sensitivity testing. The wound should be left open to allow for further drainage.
Bacterial infections generally resolve well after this regimen. Sharp dissection (e.g. the use of a needle) is not recommended. Treat fungal infections with systemic antifungal drugs; the prognosis is more guarded.
Retrobulbar tumors may be benign or malignant and may be treated with surgical removal (often along with removal of the eye)
and chemotherapeutic drugs.15 The prognosis is guarded depending on the type of tumor involved.15
Often it is difficult to retrieve a recognizable foreign object from the retrobulbar area. Biological material, such as splinters
and grass awns, are sometimes in the process of being autolyzed at the time of drainage of the orbit.
Some foreign objects and neoplasms can be removed surgically without disturbing the eye, while others require enucleation
to reach the depths of the orbit.8 Weigh the options carefully before removing an eye. A referral to an ophthalmologist is highly recommended if orbital surgery,
with or without enucleation, is to be considered.
Further examination of the oral cavity of the dog mentioned at the beginning of this article showed a large swelling behind
the last premolar tooth (Figure 5). The dog was anesthetized, and the swollen area was opened and drained. A grass awn and large quantities of purulent material
were found. The dog recovered without incident.
Juliet R. Gionfriddo, DVM, MS, DACVO, Department of Clinical Sciences, College of Veterinary Medicine and Biomedical Sciences,
Colorado State University, Fort Collins, CO 80523.
William C. Aaroe, DVM, Fisher's Peak Veterinary Clinic, 1617 Santa Fe Trail Drive, Trinidad, CO 81082.
To view the references for this article, visit http://dvm360.com/OrbitalRefs.