ocular emergencies

Cards (26)

  • Globe prolapse = globe is acutely displaced forwards beyond the plane of the eyelids
  • Exophthalmos = a degree of forward displacement of the globe with the eyelids remaining in a normal anatomical position
  • The process that causes a globe prolapse involves…
    • Immediate oedema of conjunctiva and orbital soft tissue
    • This is 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 has potential for corneal ulceration
    • Rupture of extraocular muscles
  • The medial rectus is often the first muscle to rupture
  • Brachycephalic breeds have shallow orbits which impart very little protection for eye. Hence, very little force is required to cause prolapse.
    • These are easy to replace and have a better prognosis
    Cats have deeper orbits and therefore better protection. Large amounts of force is required to prolapse globe e.g., Head trauma in an RTA. In these cases, the damage is very severe and the eye is unlikely to be replaced.
  • In theory, globe prolapse has a better prognosis if…
    • Brachycephalic
    • Positive PLR
    • The eye attempts to move
    There is a worse prognosis if…
    • Cat or dolicocephalic breed
    • Hyphaema
    • Corneal/scleral rupture
  • management of a prolapsed globe involves..
    • Keep globe moist with lubricating ointment (if animal allows)
    • Prevent self-trauma with a buster collar
    • Provide analgesia/sedation
    • GA for globe replacement once stable +/-clip hair
  • tarsorrhaphy = suture eyelids together
  • Clinical signs of a retrobular abscess include…
    • Acute onset
    • Unilateral
    • Exophthalmos (proptosis)
    • The direction of the proptosis depends on where the swelling is
    • Pain, especially on opening the mouth
    • Third eyelid protrusion and swelling
    • Ocular discharge
    • Pyrexia (not always)
    • Lethargy
  • If unsure there is swelling behind the eye, look from above as well as head on but also you can attempt retropulsion and the bulging eye should not be pushed back. This can be diagnosed via looking in the mouth (recall close proximity of upper dental arcade to soft tissue floor of orbit) and/or identification of a fluid-filled cavity on ultrasound. If you are opening the mouth, ensure you do this under GA, these animals are in more pain when the mouth is open and hence they are very likely to bite you.
  • To treat a retrobulbar abscess, drain the abscess under GA.
    • Access to soft tissue floor of orbit via mouth
    • Scalpel incision, insert artery forceps blindly into retrobulbar space (careful not to hit the eye)
    • Recall that most eyes are 2cm from cornea to sclera
    • Release pus
    • You can also insert a swab for C&S
  • Medical management of a retrobulbar abscess involves…
    • Systemic NSAIDS
    • Systemic antibiotics e.g., amoxiclav
    • May need IV fluids and injectable medications if not eating (hospitalization)
    • Topical lubricants until normal blinking returns
  • sudden onset blindness can be caused by…
    • Acute glaucoma
    • Acute uveitis
    • Intraocular haemorrhage
    • Retinal detachment
    • Optic neuritis (may respond to immunosuppressive treatment)
    • SARD (Sudden Acquired Retinal Degeneration, this can't be treated)
    • Toxicity (ivermectin, enrofloxacin in cats)
    • Intracranial lesion
  • The following ulcers require urgent treatment…
    • Deep corneal ulcers
    • Descemetoceles
    • Perforated corneal ulcer +/-iris prolapse
  • Acid and alkali injuries cause immediate loss of epithelium to the cornea and eyelids. These cases need immediate irrigation of the ocular surface…
    • If at home, tap water is fine
    • Tap water or saline or Hartmann’s solution if animal in the practice
  • with chemical injuries, flush copiously e.g. 500ml to 1 litre until pH normal (7.5), sedation is likely to be necessary. Test the pH of the conjunctival sac to determine the nature of the chemical e.g. urine dipstick and seek early specialist advice.
    • If you do not know what the chemical was an immediate pH can help indicate
    Medical management for corneal ulceration is also needed. Alkalis may induce ‘melting’ or liquefactive necrosis hence, intensive medical management indicated with prophylaxis;
  • acute glaucoma = Increased pressure in the eye due to an increase in fluid, this is most commonly due to inadequate drainage of the eye. Normally this starts as unilateral but will become bilateral over time.
  • acute glaucoma presents with…
    • Ocular pain (classic triad) involves…
    • Blepharospasm
    • Increased lacrimation
    • Photophobia
    • Head shy, yelping, dull/quiet
    • Vision loss
    • Change in appearance e.g., a fixed dilated pupil (pressure on the optic nerve and damage to the muscles in the iris, episcleral vessel congestion and a cloudy eye
  • Two groups of dogs are predisposed to acute glaucoma…
    • Purebred dogs with hereditary primary glaucoma (Spaniels, retrievers, Bassets, huskies…)
    • These are born with poor drainage but are able to compensate for a period of time. Once this compensation fails, an acute glaucoma occurs.
    • Terrier breeds with acute lens luxation and secondary glaucoma
    • As the luxated lens blocks drainage
    • Acute glaucoma often has an IOP greater than 40mmHg, it is possible to see IOPs of 60-80mmHg
  • Treatment of acute glaucoma involves…
    • Reduction of IOP, the choice of medications depends on underlying cause
    • Prostaglandin analogue (latanoprost) if suspect primary
    • Carbonic anhydrase 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 so consider referral assessment of other eye if this is the diagnosis
    • Referral centres can assess the drainage angle in the remaining eye
  • Unfortunately, most acute glaucoma cases result in enucleation and if performed, send the eye for histopathology to identify the cause of the acute glaucoma.
  • Lens luxation can be…
    • Primary: hereditary (terrier breeds) weakness in lens zonules
    • If a terrier, assume anterior lens luxation (rather than primary glaucoma) until proven otherwise!
    • Secondary: may follow glaucoma, uveitis, cataract
  • The lens may move anteriorly or posteriorly, anterior lens luxation is an ophthalmic emergency.
  • The clinical signs of an anterior lens luxation includes…
    • An acutely painful eye
    • Glaucoma (episcleral injection, raised IOP, diffuse oedema and vision loss)
    • Focal corneal oedema
    • Lens outline may be visible in the anterior chamber (see RHS)
  • In cases of anterior lens luxation, offer referral for emergency surgical removal of lens or “couching” to push lens backwards (plus drops to keep the lens there). These cases must receive analgesia e.g. oral NSAID and opioid. After treatment, these cases require ongoing management as anterior lens luxation is a bilateral condition. This means the contralateral eye is likely to be affected but at an earlier stage i.e. subluxation. Hence, consider referral assessment/prophylactic treatment (removal of the lens before it completely luxates)