Ophthalmic emergencies

• What is traumatic proptosis?

  Globe prolapse - the globe is acutely displaced forwards beyond the plane of the eyelids, so the eyelids are basically stuck behind the eye.

  
• What is the pathophysiology of globe prolapse?

  Immediate oedema of conjunctiva and orbital soft tissue - further exacerbated by the eyelid spasm (obstructs venous drainage leading to more swelling).

  Traction on optic nerve likely to result in permanent blindness.

  Desiccation of ocular surface - potential for corneal ulcers.

  Rupture of extra-ocular muscles.

  7 extra ocular muscles, medial Rectus tends to be the first to go.
• Brachycephalic breeds and orbit shapes

  Shallow orbits impart very little protection for the eye.

  Very little force required to cause prolapse.

  Easy to replace, better prognosis.
• Feline globe prolapse

  Cats have deeper orbits and therefore better protection.

  • Large amount of force required to prolapse globe, therefore the damage will be quite severe.
  • Head trauma in an RTA.
  • Circled is the optic nerve.
  • Have to decide whether or not to remove the eye.
• How do you treat a globe prolapse?

  Needs treating immediately: by you rather than by referral.

  Rapid treatment will improve prognosis for vision and globe.

  Distressing to animal and owner.

  Painful.

  Keep the globe moist - lubricating ointment.

  Prevent self-trauma with a buster collar.

  Provide analgesia/sedation.

  GA for globe replacement once stable.

  Surgery is a lateral canthotomy.
• What is the aftercare for a globe prolapse?

  Systemic antibiotics and anti-inflammatory ems (synulox).

  Broad spectrum topical antibiotics.

  Buster collar.

  Re-evaluate after 10-15 days to remove sutures and decide if enucleation is required.
• What is the prognosis for globe prolapses?

  Must manage owners expectations.

  Prognosis for vision is guarded as most eyes are blind.

  Prognosis for retaining the globe is reasonable (most owners prefer a blind eye to no eye).

  Can cause other complications:

  • Lagophthalmos - can’t blink
  • Neutrophic keratitis - animal can’t feel surface of the eye.
  • Dry eye
  • Permanent strabismus (eye drifts off to one side)
• What is a retrobulbar abscess?

  Abscess or cellulitis behind the globe.
• What are the clinical signs for retrobulbar abscess?

  Acute onset

  Unilateral

  Exophthalmos (proptosis)

  Pain, especially on opening the mouth.

  Third eyelid protrusion and swelling.

  Ocular discharge

  Pyrexia, lethargy

  Inappetence.
• How do you diagnose a retrobulbar abscess?

  Ultrasound - look for fluid-filled cavity.

  Look in mouth - recall close proximity of upper dental arcade to soft tissue floor of orbit.

  
• How to treat a retrobulbar abscess?

  Drain abscess under GA.

  Access to soft tissue floor of orbit via mouth.

  Scalpel incision, insert artery forceps blindly into retrobulbar space.

  Recall that most eyes are 2cm from cornea to sclera, careful not to puncture the eye.
• What is the medical management for a retrobulbar abscess?

  Systemic NSAIDs

  Systemic antibiotics

  May need IV fluids and injectable medications if not eating.

  Topical lubricants until normal blinking returns.
• What are the clinical signs of acute glaucoma?

  Ocular pain (classic triad):

  • Blepharospasm
  • Increased lacrimation
  • Photophobia

  Head shy, yelping, dull/quiet

  Vision loss

  Change in appearance.
• What are the signs you see in eyes that show acute glaucoma?

  Corneal oedema (when IOP >40mmHg)

  Episcleral vessel congestion.

  Fixed dilated pupil (no PLR), pressure on the optic nerve stops the sight, also stop the iris muscles from contracting.

  
• What breeds are predisposed to acute glaucoma?

  Purebreed dogs with hereditary primary glaucoma:

  • Spaniels
  • Retreivers
  • Bassets
  • Huskies.

  Terrier breeds with acute lens lucations and secondary glaucoma
• How do you diagnose acute glaucoma?

  Via Tonometry - measure the IOP.

  Normal range in dogs and cats is 10-25mmHg

  Acute glaucoma:

  • Often >40mmHg
  • May see IOPs of 60-80mmHg
• What is the treatment for acute glaucoma?

  Reduce IOP - choice of medications depends in underlying cause:

  • Prostaglandin analogue (Iantanoprost) if suspect primary, acts to increase outflow of aqueous humour, most effective drug.
  • Carbonic anhydrise inhibitors (brinzolamide, dorzolamide) always ok.
  • IV mannitol if not responding to drops.

  Analgesia

  Seek referral advice/offer referral ASAP.

  Primary glaucoma is a bilateral condition:

  • Consider referral assessment of the other eye.
  • If eye is enucleated, send for histopathology.
• What are the causes of lens luxation?

  Primary - hereditary weakness in lens zonules, terrier breeds are predisposed.

  Secondary - may follow glaucoma, uveitis, cataract.

  Lens may move anteriorly or posteriorly - anterior lens luxation is an ophthalmic emergency (tends to happen in terriers).
• What are the clinical signs for lens luxation?

  Acutely painful eye

  Lense blocks the drainage causing glaucoma (episclera injection, raised IOP, diffuse oedema, vision loss).

  Focal corneal oedema.

  Len outline may be visible in the anterior chamber.
• How do you decide if it is a lens luxation or primary glaucoma?

  Does the dog have a history of either problem?

  If very cloudy:

  • Take photo with a flash can highlight the edge of the lense in the anterior chamber.
  • Consider ultrasound.

  Look at the eye for clues - bilateral condition.
• What is the treatment for anterior lens luxation?

  Offer referral: emergency surgical removal of lense or ‘couching’ to push the lense backwards.

  Analgesia e.g. oral NSAID and opioid.
• What are corneal emergencies?

  Chemical injury

  FB

  Melting ulcer

  Severe lacerations.
• What are chemical injuries of the cornea?

  Acid and alkali injuries cause immediate loss of epithelium.

  Cornea and eyelids.

  Acid injuries

  • Bleach, toilet cleaner.
  • Spirit-based skin preparation.

  Alkali injuries:

  • Caustic solutions.
  • Lime burns (e.g. cement, plaster)
  • Washing detergents.
• What is the treatment for chemical injuries?

  Immediate irrigation of ocular surface:

  • If at home, tap water is fine.
  • Flush copiously e.g. 500ml-1L until the pH is normal (7.5); sedation likely to be necessary.

  Test pH of conjunctival sac to determine nature of chemical e.g. urine dipstick - if not sure what the chemical was, use a dipstick to start with to find out.

  Early specialist advice.

  Medical management for corneal ulceration
• Corneal ulcerations

  Prognosis depends on extent of injury e.g. whether intraocular structures are involved.

  Consider referral.

  Tends to be a cat claw injury.

  The bulging but is iris coming out, the eye is also fill of blood.
• What are the causes of sudden onset blindness?

  Acute glaucoma

  Acute uveitis

  Intraocular haemorrhage

  Retinal detachment

  Optic neuritis

  SARD (sudden acquired retinal degeneration).

  Toxicity (ivermectin, enrofloxacin in cats)

  Intracranial lesion.