Diagnosing Canine Exophthalmos

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Jessica McDonald, DVM Amy Knollinger, DVM, DACVO Eye Care for Animals Salt Lake City, Utah

1 d Left eye of a 14-year-old dog with unilat- eral exophthalmos. Note the third eyelid protrusion, dorsolateral deviation of the globe, ventral deviation of the third eyelid, and epiphora in the medial canthus.

YOU HAVE ASKED... globe) resulting from a chronic increase in intraocular pressure or glaucoma.1-3 What is the best way to diagnose Readers are advised to read “Differentiat- and treat exophthalmos in dogs? ing Exophthalmos, Buphthalmos, & Pro- ptosis” (Clinician’s Brief, cliniciansbrief. Retropulsion com/differentiating-exophthalmos) on can help discern this topic. Retropulsion can help discern THE EXPERTS SAY... the compressibility the compressibility of the orbital con- of the orbital Diseases in the orbit are uncommon tents, which is limited with a space-occu- contents, which and typically produce clinical signs by pying lesion. This is performed by closing is limited with a changing the volume and/or function of the eyelids over the globe and pushing the orbital structures. In the early stages the globe into the orbit (Figure 2, next space-occupying of orbital disease, clinical signs are gen- page). lesion. erally nonspecific and may include mild prolapse of the third eyelid, periorbital If a space-occupying lesion is present, swelling, temporomandibular pain, globe displacement within the orbit may anisocoria, blindness, exophthalmos vary depending on the location. Space- (protrusion of the eyeball), enophthal- occupying lesions within the extra- mos (posterior displacement of the eye- ocular muscle cone generally push the ball), or deviation of the globe globe straight forward, whereas lesions (strabismus; Figure 1).1,2 outside the extraocular muscle cone push the globe opposite the location of Exophthalmos should be differentiated the lesion.2 The onset of clinical signs from buphthalmos (increased size of the can also help determine the cause of

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Advanced imaging procedures (eg, MRI, CT) have become the gold standard for orbital imaging. Like ultrasonography, CT can be used to guide biopsy and pro- vide a definitive diagnosis. These modalities can identify foreign bodies, locate lesions, and define the extent of disease. This can be used for diagnostic and treatment planning as well as prognosis.4

Common Causes of 2 Orbital Disease Diagnostic differentials for orbital dis- d Image of retropulsion performed on a dog. ease can be extensive, and a thorough The upper eyelid is closed and the globe is pushed workup is needed before treatment can into the orbit. This can be performed in both eyes begin. This article focuses on the more simultaneously to determine if there is any difference common causes; Other Causes of in retropulsion between the eyes. Orbital Disease in Dogs lists additional causes.

orbital disease. Acute onset is more consistent with inflammatory disease; slower onset is more suggestive of a neoplastic process, mucocele, or cyst.2 OTHER CAUSES OF ORBITAL DISEASE IN DOGS1 Orbital Disease Diagnostics h Orbital neoplasia: primary or secondary Many diagnostic tests and procedures h Retro-orbital neoplasia: bone, sinuses, can be performed to evaluate orbital nasal and oral cavity disease. A general physical examination is helpful for diagnosing orbital disease. h Orbital abscess Apparent pain when palpating around h Orbital cellulitis the periorbital region as well as pain h Retro-orbital cellulitis/abscess: tooth on opening the mouth (as a result of root, zygomatic sialadenitis, foreign body, compression of the abnormal orbital fungal granuloma contents by the ramus of the mandible) can be indicative of orbital disease. Pain h Orbital mucocele: zygomatic origin is most consistent with an inflammatory h Orbital cysts process but can also be present if an h Orbital hemorrhage: trauma, blood advanced neoplasia is present. Although dyscrasia, clotting deficiencies skull radiography is often low-yield and nonspecific, it can be used to detect h Arteriovenous fistula involvement of the adjacent nasal cavity, h Myositis of ocular muscles sinuses, or tooth roots. Ultrasonography h Myositis of muscles of mastication can be used to identify orbital lesions for guided biopsy but is also often low-yield. h Mandibular hypertrophic osteoarthropathy

76 cliniciansbrief.com May 2016 3A 3B d ( A) Axial T2-weighted and (B) sagittal T2-weighted postcontrast MRI images of the dog in Figure 1 with a mixed orbital carcinoma. Note the lobular mass ventromedial to the left eye. It is causing dorsolateral distortion of the ventral globe.

Orbital Neoplasia Orbital Abscess Orbital neoplasia (Figure 3) can be clas- Retrobulbar abscesses causing acute, sified as primary (involving the orbital moderate-to-severe exophthalmos are tissue directly) or secondary (arising typically painful. Treating an orbital from a distant site or extension of a con- abscess empirically with an extended tiguous structure). Approximately 90% course of medications for at least to 95% of all orbital neoplasias are 4 weeks may be sufficient, especially malignant in the dog and cat,2 with 92% early in the course of disease. Antibiot- and 58% being primary in the dog and ics (against both aerobic and anaerobic cat, respectively.5 Orbital neoplasias are organisms), NSAIDs, and pain medica- usually associated with slowly progres- tions should be used. Oral corticoste- sive exophthalmos and minimal pain, roids should be avoided if in doubt about although approximately one-third of the presence or absence of infection. A orbital neoplasias are painful.2 MRI or topical lubricant is indicated if lagoph- CT is used to localize and define the thalmos (inability to perform a com- margin of orbital tumors. Usually, plete blink response) is present. If excision of these tumors is not curative. lagophthalmos is severe, a temporary Orbital exenteration—removal of all tarsorraphy should be performed. Topi- orbital contents, including the globe—is cal corticosteroid medications are con- advised, even in a visual eye. Consulta- traindicated because of the increased tion with a veterinary oncologist for risk for corneal ulceration caused by potential chemotherapy or radiation corneal exposure. Lubricants without an therapy is strongly recommended owing antibiotic are indicated if no evidence of to the aggressive, malignant nature of ocular surface infection or corneal these tumors.1-3,5 ulceration is present.

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Recurrence after stopping medical ther- quate treatment. Blindly draining any apy may require surgical exploration or inflammatory process via the mouth is referral to a veterinary ophthalmolo- not advised, as excessive damage to the gist. Abscesses can be drained under optic nerve and associated orbital struc- general anesthesia. The oral mucosa tures can occur with minimal-to-no behind the last upper molar tooth is drainage. often swollen and inflamed. The mucosa is incised and closed hemostats are Orbital Mucocele introduced into the orbit through the Orbital retention cysts or mucoceles may incision. The hemostats are opened and arise from the zygomatic salivary gland, withdrawn without closing to establish lacrimal glands, conjunctiva, or parana- drainage of the abscess. If no improve- sal sinus mucosa. The typical presenta- ment is noted or the globe is blind, tion is nonpainful exophthalmos enucleation or exenteration can be con- accompanied by a prominent third eye- sidered for comfort purposes. lid. A fluctuant conjunctival swelling may be found on ocular examination, or Orbital Cellulitis swelling of the zygomatic salivary duct or Orbital cellulitis, or inflammation within the mucosa behind the last upper molar the orbit, is typically acute and may be may be found on oral examination. Typi- misinterpreted as conjunctivitis in early cally, orbital mucoceles and retention stages. Retropulsion is decreased, and cysts require surgical excision; however, there can be significant pain on opening successful use of intracystic polidocanol the mouth. Extension of inflammation has also been reported.6 from a tooth root, nasal sinus, or zygomatic salivary gland can cause orbital Orbital disease is a rare, potentially dev- cellulitis, as can inflammation from astating disease of the dog that can pres- migrating or penetrating foreign bodies. ent in many different ways, especially in Depending on the cause of infection and early disease process. Imaging with rou- the severity of exophthalmos, medical tine modalities can be difficult, therefore therapy alone, including empiric antibi- advanced imaging (eg, MRI, CT) is otics and anti-inflammatory medications highly recommended for diagnosis if for a minimum of 4 weeks, may be ade- clinical signs are observed. n

References 1. Gelatt KN, Gilger B, Kern T. Diseases and surgery of 4. Lederer K, Ludewig E, Hechinger H, Parry AT, Lamb the canine orbit. In: Gelatt KN, Gilger B, Kern T, eds. CR, Kneissl S. Differentiation between inflammatory Veterinary Ophthalmology. 5th ed, vol 1. Chicester, UK: and neoplastic orbital conditions based on computed Wiley-Blackwell; 2013:793-813. tomographic signs. Vet Ophthalmol. 2015;18(4):271- 2. Martin C. Orbit and globe. In: Gelatt KN, Gilger BC, 275. eds. Ophthalmic Disease in Veterinary Medicine. 2nd 5. Attali-Soussay K, Jegou JP, Clerc B. Retrobulbar ed. London, UK: Manson Pub. 2010:113-129. tumors in dogs and cats: 25 cases. Vet Ophthalmol. 3. Hendrix DV, Gelatt KN. Diagnosis, treatment and 2001;4(1):19-27. outcome of orbital neoplasia in dogs: a retrospective 6. Stuckey JA, Miller WM, Almond GT. Use of a sclerosing study of 44 cases. J Small Anim Pract. 2000;41(3):105- agent ( 1% polidocanol) to treat an orbital mucocele 108. in a dog. Vet Ophthalmol. 2012;15(3):188-193.

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