April 18, 2019


 In this month's Pulse article, learn more about common small animal orbital disease! Congenital microphthalmia describes an abnormally small globe, generally noted in combination with a smaller palpebral fissure and orbit. The degree of microphthalmia varies considerably, extending from only a mild decrease in size of a functional globe, to rare cases of anophthalmos, in which there is a complete absence of ocular tissue. Changes are generally bilateral. There is no treatment for microphthalmia, however in severe cases, secondary conjunctivitis may require either medical management or the enucleation of residual ocular tissues.


Phthisis bulbus describes a “shrunken” eye, typically as a result of severe and/or chronic intraocular inflammation, infection or aqueous humor leakage. Clinically, affected globes are blind and may display reduced size, corneal fibrosis, uveal adhesions, cataracts and/or retinal detachment. Treatment may comprise benign neglect in comfortable patients, the medical management of secondary conjunctivitis or enucleation if indicated.

Orbital cellulitis describes inflammation of the periocular tissues. Findings may include blepharospasm, conjunctivitis, chemosis, third eyelid elevation, ocular discharge, deviation of the globe from its normal position, secondary exposure keratitis, periocular swelling/fluctuance and/or difficulty opening the mouth as a result of pressure placed on inflamed retrobulbar soft tissues by the ramus of the mandible. Symptoms typically develop relatively rapidly (over the course of several days). This process may result from trauma, penetrating wounds, extension of inflammation/infection from adjacent tissues (such as dental disease) and/or the presence of foreign material. Evaluating patients affected by orbital cellulitis can be challenging as result of patient discomfort and sedation or anesthesia is frequently required in order to fully assess affected structures. The diagnosis is made based on clinical findings in conjunction (where indicated) with adjective diagnostics including CBC/chemistry analysis, ultrasonography, radiography and/or magnetic resonance imaging.  Microbial samples may support initial diagnostic finings, including culture & sensitivity testing where the presence of infectious organisms is suspected as well as cytology (FNA) and/or histopathology (biopsy) where appropriate.

Therapy comprises the institution of drainage where abscessation has developed as well as the institution of systemic (broad spectrum) antimicrobial and anti-inflammatory therapy. 

Occasionally a partial prolapse of the orbital fat pad may be noted in dogs, and less commonly in cats. Fat prolapse results from either congenital or traumatic weakness associated with orbital soft tissues. The diagnosis may be confirmed by cytological or histological evaluation of representative fine needle aspirate or biopsy samples respectively. The major differential for fat pad prolapse is represented by neoplastic tissue, notably benign hibernomas but occasionally malignant liposarcomas. If indicated, prolapsed tissue may be surgically excised and surrounding soft tissue imbricated. 

Proptosis describes partial or complete dislocation of globe from its normal position with the orbit, typically as a result of trauma. Secondary entrapment by severely swollen periorbital tissue is common. Other associated symptoms may include subconjunctival hemorrhage, episcleral hemorrhage, hyphema and/or exposure keratopathy.

Negative prognostic indicators include;

·      Multiple extraocular muscular avulsions

·      corneoscleral rupture

·      hyphema

Positive prognostic indicators include;

·      Significantly brachycephalic conformation

·      Minimal globe displacement

·      Miotic pupil and/or the presence of a pupillary light reflex (PLR)

Initial treatment of ocular proptosis encompasses addressing potentially life-threating injuries and stabilizing the patient. Consideration should be given to enucleating severely traumatized globes, which are unlikely to be salvageable.  The ocular surface should be moistened with physiologic fluids, prior to globe replacement under general anesthesia, which may necessitate canthotomy. Temporary tarsoraphy sutures are typically placed following proptosis reduction and left in place for 10-14 days. Potential complications following proptosis include permanent strabismus, ulcerative keratitis, KCS, neuroretinal degeneration and/or phthisis bulbi.

Retrobulbar neoplasia is not uncommon, with most orbital neoplasms being both primary & malignant. Prevalent tumor types include carcinoma (squamous cell carcinoma & adenocarcinoma), sarcoma (spindle cell sarcomas, fibrosarcoma, hemangiosarcoma, multilobular orbital sarcoma, osteosarcoma & chondrosarcoma), meningioma and lymphoma. Clinical findings may include blepharospasm, conjunctivitis, chemosis, third eyelid elevation, ocular discharge, deviation of the globe from its normal position, secondary exposure keratitis, peri-ocular swelling/fluctuance and/or difficulty opening the mouth, visual and/or neurological defects. Symptoms typically develop relatively slowly (over the course of weeks to months), with most patients remaining comfortable until changes are significantly advanced.  Affected patients are typically older. Diagnostic modalities useful for the investigation of orbital disease include radiography, ultrasonography, computed tomography and/or magnetic resonance imaging. The diagnosis is made based on evaluation of samples harvested by FNA or biopsy, typically post-imaging. Treatment may include any combination of surgical resection where possible (potentially involving enucleation/extenuation), systemic chemotherapy and/or radiation therapy based on the tumor type present.

Dr Esson is a board-certified veterinary ophthalmologist with more than twenty years of clinical experience and multiple areas of interest & expertise. His clinicVeterinary Ophthalmic Consulting is family owned & operated and he takes great pride & pleasure in working closely with his friends and colleagues in the greater Southern California veterinary community.

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To find a complete list of ophthalmic eye conditions related to this article, please click here.