Globe Proptosis – Canine

Published by Rachel (Mathes) Davis, DVM, MS, DACVO July 2016
Publication: Veterinary Information Network (VIN)

Disease Description

Proptosis is the sudden expulsion of the globe from the orbit causing the globe to be positioned anterior to the eyelids and the eyelids to become entrapped posterior to the globe.  Globe proptosis is due to orbital trauma, either blunt, shearing or penetrating.  A detailed history is important to determine the type of trauma sustained, which may help the practitioner to further evaluate the patient for systemic or other craniofacial trauma.  In some cases, the nature of the trauma may be inferred, but is not actually known.

Etiology

Globe proptosis occurs secondary to orbital or craniofacial trauma (e.g. dog fight, vehicular trauma), although the trauma sustained may be minimal in brachycephalic dogs.¹  Orbital trauma is typically significant in mesocephalic and dolichocephalic dogs with globe proptosis² and evaluation for presence of concurrent facial skull fractures, subcutaneous emphysema, epistaxis, periocular tissue damage and neurologic deficits as well as systemic traumatic lesions should be performed.

Diagnosis

Ophthalmic Examination Findings: Diagnosis is straightforward and made upon identification of the globe anterior to the orbit and eyelids with entrapment of the eyelids posterior to the globe.  There may be concurrent mild to severe orbital or head trauma present often seen as periocular subcutaneous emphysema, soft tissue swelling, skin lacerations or palpable skull fractures.  When assessing a proptosed globe, it is important to assess both the periocular structures and globe viability.  In dogs, there is a favorable prognosis for vision in brachycephalic breeds, presence of direct pupillary light response, presence of vision, visualization of the fundus and presence of indirect pupillary light response to the contralateral eye.¹  There is a favorable prognosis for globe salvage if any of the vision indicators are present and if there is absence of extraocular muscle damage, avulsion of less than two extraocular muscles or minimal to no intraocular hemorrhage.^1,2 Pupillary size at presentation is of no prognostic value.  Poor prognostic indicators for globe salvage include proptosis in a mesocephalic and dolichocephalic breeds, hyphema, optic nerve damage, concurrent facial fractures or avulsion of two or more extraocular muscles.²

Physical Examination Findings: Because globe proptosis is secondary to trauma, a thorough physical examination should be performed to assess for any other systemic signs of trauma.

Disease Description in this Species

Signalment

Brachycephalic dogs are at higher risk of globe proptosis² secondary to their conformational exophthalmos, relatively shallow orbits, globe exposure and macropalpebral fissures with brachycephalic dogs representing 14 of 29 dogs affected with globe proptosis in one study.³  Young dogs (mean age 5.2yrs) have also been shown to be at higher risk of globe proptosis.³

Clinical Signs

Dogs are typically presented on an emergent basis after sustaining head trauma.  Because the appearance of a proptosed globe is somewhat disturbing aesthetically, most clients will be distraught when bringing their pet to the veterinary clinic.  Diagnosis is easily made based on visual appearance of the globe anterior to the orbit and eyelids.

Etiology

• Trauma
• Breed conformational skull abnormalities (breed predisposition)

Breed Predilection

Brachycephalics

Sex Predilection

None

Age Predilection

Young dogs

Diagnostic Procedures

Ophthalmic examination – globe positioned anterior to eyelids and orbit, absent menace and palpebral reflex secondary to entrapment of eyelids posterior to globe, +/- vision, +/- absent direct pupillary light response, +/- absent indirect pupillary light response from affected to non-affected eye, +/- hyphema, +/- corneal ulceration secondary to exposure and corneal drying, +/- severed extraocular muscles, +/- severed optic nerve

Physical examination – variable periocular swelling, periorbital lacerations, subcutaneous emphysema, skull fractures, epistaxis, other systemic signs of trauma

Treatment/Management/Prognosis

Specific Therapy

Damage to the globe, optic nerve and periocular structures is sustained at the time of the trauma, thus immediate replacement of the globe after presentation will not improve prognosis for vision.  However, prompt replacement of the globe will help decrease incidence of corneal ulceration and prevent severe swelling of the conjunctiva and eyelids due to decreased venous return.⁴  Thus, globe proptosis is considered a true ophthalmic emergency and the globe should be reduced as soon as possible if it is a good candidate for reduction.  The corneal surface should immediately be lubricated upon presentation with a viscous lacrimomimetic (e.g. artificial tear ointment) to help avoid ulceration during ophthalmic and physical examination.

Although the patient will not be able to close the palpebral fissure due to entrapment of the eyelids posterior to the globe, a positive menace or dazzle response in a visual eye may still be noted by movement of the eyelids or movement of the head away from the stimulus.  Additionally, an indirect pupillary light response from the proptosed eye to the unaffected eye may be used to assess for globe viability.  Even if the globe is not deemed viable, replacement may be attempted if the periorbital and periocular tissues appear intact.  Because the medial rectus muscle is the shortest extraocular muscle, this muscle is often damaged or transected during globe proptosis.¹  Thus, permanent lateral strabismus may be noted in reduced globes.  With transection of one or more extraocular muscles, permanent strabismus may cause increased corneal exposure or poor eyelid closure leading to chronic corneal ulceration, chronic keratitis or corneal infection and melting, necessitating enucleation later.  The client should be educated regarding the possibility of permanent strabismus, decreased ocular motility, absence of vision or need for enucleation of the globe later. Transection of two or more extraocular muscles is considered a grave prognostic indicator and globes sustaining this level of injury should be enucleated.²

Globe reduction should be performed with the patient under general anesthesia.  Local anesthetic retrobulbar blocks are not recommended as they may cause further orbital and periocular tissue swelling.  After induction of anesthesia, the periocular tissues should be gently clipped and cleaned with dilute betadine (1:10) solution.  The corneal surface should be generously lubricated with artificial tear ointment or other viscous lubricant.  After cleaning, strabismus hooks may be used around the eyelids to manipulate them anterior and away from the globe back to a normal position.¹ Because most clinics do not have strabismus hooks readily available, towel clamps or Allis tissue forceps may be used to grasp the dorsal and ventral central eyelids as close to the margin as possible without damaging the globe or conjunctiva.  The eyelids should be manipulated simultaneously away and anterior to the globe while gentle manual pressure is concurrently applied to the cornea, usually with an assistant.  A lateral canthotomy may be performed to aid in globe reduction if there is significant swelling or if the globe is difficult to reduce manually.¹  After reduction, two temporary tarsorraphies (one central and one lateral) should be placed in the eyelids to prevent re-proptosis during the healing phase.⁵  The tarsorrhaphies should be placed with 3-0 to 5-0 suture with stents (e.g. rubber bands or IV tubing) in the horizontal portion of the tarsorrhaphy to prevent eyelid suture pressure and laceration.⁶  A small medial opening should be allowed for medication administration topically.

If the globe is enucleated, accessory adnexal structures (i.e. eyelid margins, third eyelid, conjunctiva) should be carefully excised to avoid complications from residual adnexal tissue.⁷

Supportive Therapy

After reduction/replacement of a proptosed globe, systemic anti-inflammatory (e.g. carprofen 2.2mg/kg BID PO) and analgesic (e.g. tramadol 2-4mg/kg PO TID-BID) therapy is recommended for 5-7 days.  Oral antibiotic therapy may also be warranted depending on the soft tissue injury sustained during the trauma.¹ Topical antibiotic and lacrimomimetic therapy (e.g. triple antibiotic ointment TID or triple antibiotic solution TID and artificial tear ointment TID) is recommended for 10-14 days after globe replacement.  Topical steroids are typically not recommended after globe reduction as they may potentiate corneal melting if an ulcer occurs secondary to proptosis or reduction surgery.

Monitoring and Prognosis

After globe reduction, the patient should be re-evaluated in 5-7 days, at which time, the central tarsorrhaphy may be removed.  Both tarsorrhaphies may be removed if there is significant eyelid irritation or pressure ulcers secondary to tarsorrhaphy stents.  Ideally, the lateral tarsorrhaphy should remain in place for 10-14 days to allow complete healing of the periocular and orbital tissue.  Globe motility should be assessed once all tarsorrhaphies are removed as well as vision and corneal integrity with fluorescein staining.  Quantitative tear assessment should also be performed as keratoconjunctivitis sicca may be a complication after globe reduction.²  Other known complications after reduction of globe proptosis include blindness, strabismus (especially exotropia or lateral strabismus), exposure keratitis, lagophthalmos and glaucoma, thus long term periodic evaluation is warranted.² Globes causing recurrent or ongoing discomfort to the patient should be enucleated.

Differential Diagnosis

• Exophthalmos secondary to orbital mass
• Orbital fractures

References

1. Spiess BM. Diseases and Surgery of the Canine Orbit. In Gelatt KN (ed): Veterinary Ophthalmology 4^th Pp 547-549
2. Gilger BC, et al. Traumatic ocular proptoses in dogs and cats: 84 cases (1980-1993). J Am Vet Med Assoc 1995
3. Fritsche J, et al. Prolapse of the eyeball in small animals: a retrospective study of 36 cases. Tierarztl Prax 1996
4. Mandell DC. Ophthalmic emergencies. Clin Tech Small Anim Pract 2000
5. Cho J. Surgery of the globe and orbit. Top Companion Anim Med 2008
6. Stades FC, Gelatt KN. Diseases and Surgery of the Canine Eyelid. In Gelatt KN (ed): Veterinary Ophthalmology 4^th Pg 612
7. Ward AA, Neaderland MH. Complications from residual adnexal structures following enucleation in three dogs. J Am Vet Med Assoc 2011