Orbit: cellulitis in Horses (Equis) | Vetlexicon
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Orbit: cellulitis

ISSN 2398-2977

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  • Unilateral diffuse painful peri-ocular soft tissue swelling.
  • Cause: results from invasion of opportunistic bacteria into soft tissues around globe - secondary to small puncture wounds of eyelid/conjunctiva, orbital trauma, head trauma, or upper respiratory tract disease.
  • Signs: unilateral diffuse painful peri-ocular soft tissue swelling with ocular pain and discharge, pyrexia and third eyelid protrusion.
  • Treatment: systemic antibiotics and NSAIDs essential.
  • Prognosis: guarded.

Presenting signs

  • Diffuse, painful peri-orbital soft tissue swelling.
  • Minor injuries to eyelid/palpebral conjunctiva.
  • Unilateral.
  • Ocular pain and discharge.
  • Pyrexia.
  • Concurrent head or upper respiratory tract infections.
  • Orbital/facial trauma.

Cost considerations

  • Loss of eye and enucleation.
  • Treatment costs.



Predisposing factors

  • As above.


  • Orbital cellulitis results from the invasion of opportunistic bacteria into the soft tissues around the globe within the peri-orbita.
  • Infection can spread from the nose, mouth or paranasal sinuses via common venous drainage routes or be introduced more directly via orbital trauma or small eyelid/conjunctival puncture wounds.
  • Severe orbital inflammation or infection may eventally damage the optic nerve.
  • Direct or indirect introduction of infection into the orbit can lead to a diffuse orbital cellulitis or be localized and form a retrobulbar abscess   Orbit: retrobulbar abscess  .
  • Severe orbital inflammation often initially does not affect the eye but damage may occur to the optic nerve.
  • In advanced cases exophthalmos and exposure keratopathy can develop.


  • Sometimes as little as 24-48 h.


Presenting problems

Client history

  • Minor injuries to eyelid/palpebral conjunctiva - often self-inflicted on a sharp object and not always recognized.
  • Sudden onset severe swelling around eye with pain and discharge.
  • Orbital/facial trauma with obvious skin lacerations.
  • Previous or concurrent infections/inflammations of nose, mouth or upper respiratory tract.

Clinical signs

  • Diffuse painful periorbital/periocular soft tissue swelling including supra-orbital fossa and eyelids.
  • Often unilateral and acute.
  • Congenital chemosis and hyperemia   Conjunctiva: chemosis (conjunctivitis)  .
  • Pyrexia.
  • Serous to mucopurulent ocular discharge.
  • Exophthalmos with secondary exposure keratopathy.
  • Protrusion of third eyelid   Third eyelid: prolapse  .
  • The intra-ocular appearance of the eye may be normal but optic nerve hyperemia and papilledema   Optic disk: papilledema - EHV    Optic disk: papilledema - neuritis  do occur and are a poor prognostic indicator.

Diagnostic investigation



Radiography Hematology
  • Clinical pathology - hematology.

Confirmation of diagnosis

Discriminatory diagnostic features

  • History and clinical signs.

Definitive diagnostic features

  • Ultrasonography.

Gross autopsy findings

  • Evidence of orbital trauma, puncture wounds of eyelids/conjunctivae.
  • Pathology of upper respiratory and alimentary tracts, eg guttural pouch infections, paranasal sinusitis, dental disease.
  • Focal abscesses and sinus tracts in the supraorbital fossa and lateral/ventrolateral aspects of orbit.

Differential diagnosis


Periocular swellings

Inflammatory disease


Standard treatment

  • Immediate and intensive treatment.
  • Systemic broad spectrum bactericidal antibiotics - if samples for bacterial culture and sensitivity are available specific antibiotics should be used.
  • Systemic NSAIDs for analgesia and anti-inflammatory action to decrease edema and pressure on globe.
  • Topical antibiotic and artificial tear solutions or ointments q8h to protect corneal function when eyelid function is compromised.
  • Treat any predisposing condition including wounds or upper respiratory/alimentary tract disease.
  • Drain/aspirate/lavage any focal abscesses via external skin surface, or caudal maxillary sinus via cranial floor of orbit.
  • Warm compresses to relieve soft tissue swelling.

Subsequent management


  • Changes in antibiotics may be necessary if there is poor response or culture results change.
  • Prolonged therapy for up to several weeks may be necessary.



  • Prompt treatment of eyelid/conjunctival lacerations and puncture wounds.
  • Treatment of upper respiratory/alimentary tract disease.



  • Guarded as inflammatory response may be severe and difficult to resolve with rapid diagnosis and treatment essential.

Expected response to treatment

  • Swelling and inflammation should substantially decrease in 3-5 days.

Reasons for treatment failure

  • Prolonged septic inflammation may damage the extraocular muscles leading to fibrosis and limited motility, orbital fat with enophthalmos and optic neuritis   Optic nerve: neuritis  with atrophy .

Further Reading