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Basics ⬇

Basics

Overview

  • Forward displacement of the globe, with the eyelids trapped behind the globe's equator.
  • Frequently acute and due to bite wounds, head trauma.
  • Vision threatening.
  • Immediate repositioning of the globe critical if eye is salvageable.

Signalment

  • More common in the brachycephalic breeds due to a relatively shallow orbit and large palpebral fissure.
  • May occur in any species or breed if the traumatic force is severe enough.

Signs

Possible Accompanying Signs

  • Subconjunctival or intraocular hemorrhage.
  • Abnormalities in pupil size-dilated or constricted.
  • Intraocular inflammation (uveitis).
  • Globe deviation/strabismus/rupture.
  • Corneal ulceration/desiccation.
  • Periocular bite wounds.
  • Fractures of the bony orbit or skull.
  • Systemic injuries.
  • Trauma to the contralateral eye.

Causes & Risk Factors

  • Trauma-primary cause; relatively minor force (restraint) in brachycephalic breeds; usually severe force in dolichocephalic and mesocephalic breeds.
  • Space-occupying retrobulbar lesion-secondary cause: rare.

Diagnosis ⬆ ⬇

Diagnosis

Differential Diagnosis

  • Buphthalmia-globe enlargement; rarely acute.
  • Exophthalmia-forward displacement of the globe due to a retrobulbar space occupying lesion; may be acute, rarely peracute.

CBC/Biochemistry/Urinalysis

Normal, unless trauma-related abnormalities present.

Imaging

Skull CT or radiographs-may show fractures due to trauma. Further diagnostic workup indicated if suspect other systemic injuries.

Treatment ⬆ ⬇

Treatment

Repositioning the Globe

  • As soon as safely possible.
  • Performed under sedation and local anesthesia or, if the patient is stable, under general anesthesia.
  • Lateral canthotomy-may ease tension on the eyelids and allow easier globe repositioning; not always necessary.
  • Engage the eyelid margins with eyelid forceps (e.g. Von Graefe or Allis forceps) or strabismus/muscle hooks, then pull the eyelids forward and away from the globe while protecting and gently pushing the globe back into the orbit (a lubricated scalpel blade handle can serve this function).
  • Place two or three temporary tarsorrhaphy mattress sutures (sutures emerge from the eyelid margin in line with the meibomian gland openings) with stents; suture the lateral canthotomy wound.
  • Fluorescein-stain the cornea prior to replacing the globe.
  • If the optic nerve and/or more than two extraocular muscles are severed, if the globe is ruptured, infected, or desiccated, enucleation may be the best option.

Medications ⬆ ⬇

Medications

Drug(s)

  • Systemic and topical broad-spectrum antibiotics-until sutures are removed.
  • Systemic corticosteroids-usually used at least initially; may be continued with marked periorbital and retrobulbar swelling.
  • Topical corticosteroids-to treat uveitis or hyphema, if cornea is not ulcerated.
  • Topical atropine-for intraocular inflammation or hemorrhage; relieve ciliary spasm and lower the risk of synechiae.

Contraindications/Possible Interactions

  • Topical corticosteroids-do not use with ulcerations.
  • Systemic corticosteroids-do not use with peri- or retrobulbar infection.

Follow-Up ⬆ ⬇

Follow-Up

Patient Monitoring

Suture removal-usually done sequentially, rather than all at once, starting 10–14 days after repositioning. Integrity of the globe and vision are reassessed 10–14 days after surgery.

Prevention/Avoidance

Bilateral medial and/or lateral canthoplasty to shorten the palpebral fissure and prevent future proptosis in brachycephalic breeds should be discussed with the client.

Possible Complications

  • Blindness.
  • Most patients retain a dorsolateral strabismus and slight forward displacement of the medial side of the globe due to rupture of the inferior oblique and medial rectus muscles. This may improve with time due to tissue fibrosis and contraction.
  • Decreased tear production-perform Schirmer tear tests after suture removal.
  • Corneal denervation causing neurotrophic keratitis with chronic ulceration and decreased corneal sensitivity.
  • Exposure keratitis due to forward displacement of globe, decreased tear production, facial nerve palsy and/or corneal denervation (decreased blink reflex).
  • Phthisis bulbi.

Expected Course and Prognosis

  • Most affected eyes can be salvaged; majority will be blind (especially if proptosis was caused by significant trauma: more common in dolichocephalic than brachycephalic breeds).
  • Extensive tissue damage, avulsion of more than two extraocular muscles, facial and/or orbital fractures, and corneal or scleral rupture-grave prognosis for vision and globe salvage for cosmesis.
  • Normal retinal vessels and optic nerve, normal IOP, and a short time from occurrence to repair-relatively favorable prognosis for maintaining vision.
  • Positive menace response, dazzle and/or pupillary light reflexes-good prognosis for maintaining vision (always observe the indirect pupillary light reflex in the healthy eye originating from the injured eye&excl).
  • Pupil size at the time of the injury-not necessarily an accurate prognostic indicator; mydriasis may be the result of trauma to the optic nerve (if permanent, results in blindness) or damage to the oculomotor nerve (does not affect vision). Miosis can be caused by uveitis (if the uveitis is severe enough, pupillary constriction occurs even with retinal or optic nerve damage).

Miscellaneous ⬆

Miscellaneous

Abbreviations

  • CT = computed tomography
  • IOP = intraocular pressure

Author Simon A. Pot

Consulting Editor Paul E. Miller

Suggested Reading

Miller PE. Ocular Emergencies. In: Maggs DJ, Miller PE, Ofri R, eds. Slatter's Fundamentals of Veterinary Ophthalmology, 5th ed. St. Louis, MO: Saunders, 2013, pp. 372–393.

Spiess BM, Pot SA. Diseases and surgery of the canine orbit. In: Gelatt KN, Gilger BC, Kern TJ, eds. Veterinary Ophthalmology, 5th ed. Ames, IA: Wiley-Blackwell, 2013, pp. 793–831.