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Exophthalmia

BASICS

DEFINITION/OVERVIEW

Exophthalmia is the anterior protrusion of a normal‐sized globe.

ETIOLOGY/PATHOPHYSIOLOGY

Space‐occupying swelling or mass in the orbit placing pressure on the globe, displacing it anteriorly.

SIGNALMENT/HISTORY

There is no standard signalment for this disease.

Gradual protrusion of the eye, possibly preventing blinking, and potentially anorexia are common findings in the history.

CLINICAL PRESENTATION

While it can be bilateral, exophthalmia is more commonly unilateral.

The displacement of the globe will often push the eyelids forward and cause protrusion of the nictitans, and excessive conjunctiva will be visible.

Retropulsion of the globe is met with resistance due to the presence of retrobulbar swelling.

RISK FACTORS

Husbandry

Inadequate husbandry, especially hypothermia, may predispose animals to this condition due to decreased immune function leading to retrobulbar cellulitis and/or abscessation.

Hypovitaminosis A in chelonians causes squamous metaplasia of the orbital glands and ducts, as well as decreased immune function, and may present as bilateral exophthalmia.

Others

N/A

DIAGNOSIS

DIFFERENTIAL DIAGNOSIS

It is important to first differentiate between exophthalmia and buphthalmos.

The most common cause for exophthalmia in chelonians is retrobulbar abscessation.

Other differentials include cellulitis, trauma, granulomas, neoplasia, mucoceles, and sialadenitis.

In tortoises, vascular obstruction and generalized edema have been reported to cause bilateral exophthalmia as well.

DIAGNOSTICS

Physical examination will confirm exophthalmia, but additional diagnostics are necessary to determine the cause.

Ocular ultrasound is helpful in evaluating the problem, although the scleral ossicles can limit visualization.

Advanced imaging, such as CT or MRI, is most helpful in determining the extent of the mass and if resection is possible.

Surgical exploratory of the retrobulbar space to collect biopsies and resect any masses present in the most definitive way to achieve a diagnosis but in many cases requires enucleation to reach the retrobulbar space.

A CBC may provide information on the severity of the infection/inflammation.

PATHOLOGICAL FINDINGS

Histology and culture are most useful to diagnose the cause of the exophthalmia and allow the clinician to form an appropriate treatment plan.

TREATMENT

APPROPRIATE HEALTH CARE

N/A

NUTRITIONAL SUPPORT

Additional nutritional support is not necessary if the animal is eating, but it may be necessary to tube feed or place an esophagostomy tube if the animal is anorexic.

Assessment of the diet for adequate vitamin A levels is important and should be done to rule out hypovitaminosis A as a potential cause or contributor to this condition in chelonians.

CLIENT EDUCATION/HUSBANDRY RECOMMENDATIONS

While exophthalmia can occur in any animal, those with husbandry deficiencies may be at increased risk.

In addition to medical and surgical therapy, maximizing the husbandry of the animal will improve the chances of a successful outcome.

MEDICATIONS

DRUG(S) OF CHOICE

Treatment should be based on results of culture, histology, and/or FNA.

Starting an appropriate broad‐spectrum antibiotic with a good Gram‐negative spectrum (e.g., ceftazadime 20 mg/kg IM or SQ q48–72h) and anti‐inflammatory (e.g., meloxicam 0.2–0.3 mg/kg IM or SQ q24–48h) can be helpful while test results are pending.

PRECAUTIONS/INTERACTIONS

N/A

FOLLOW‐UP

PATIENT MONITORING

Serial CBC, especially if the first one was abnormal, may provide an indication of response to treatment.

EXPECTED COURSE AND PROGNOSIS

Prognosis is related to the underlying cause of the exophthalmia.

Cellulitis and trauma have the most favorable outcomes.

Retrobulbar abscesses can be extensive and therefore carry a more guarded prognosis.

Retrobulbar neoplasia usually carries a poor prognosis because of location and inability to get clean margins.

MISCELLANEOUS

COMMENTS

N/A

ZOONOTIC POTENTIAL

Depends on the cause of the retrobulbar swelling but generally low to no zoonotic potential.

SYNONYMS

Exophthalmos

Proptosis—severe case of exophthalmia

ABBREVIATIONS

CBC = complete blood count

CT = computed tomography

FNA = fine‐needle aspiration

MRI = magnetic resonance imaging