Ophthalmic emergencies Flashcards
Describe pathophysiology of globe prolapse. What are prognostic indicators? How is it treated? What aftercare is needed? What is overall prognosis?
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 ulceration
* Rupture of extraocular muscles
Prognostic indicators
* In theory, better prognosis if:
◦ Brachycephalic
◦ Positive PLR
◦ Eye that attempts to move
* Worse prognosis if:
◦ Cat or dolicocephalic breed
◦ Hyphaema
◦ Corneal/scleral rupture
* If in doubt, attempt replacement – can enucleate later if needed
Treatment
* Keep globe moist – lubricating ointment (if animal allows)
* Prevent self-trauma with buster collar
* Provide analgesia/sedation
* GA for globe replacement once stable
* Lateral canthotomy
* Temporary tarsorraphy (suture eyelids together)
Aftercare
* Systemic antibiotics and anti-inflammatories
* Broad spectrum topical antibiotic
* Buster collar
* Re-evaluate after 10-15 days to remove sutures and decide if enucleation required
Prognosis
* Must manage owner expectations
* Prognosis for vision:
◦ Guarded
◦ Most eyes are blind (80% dogs, ?100% cats)
* Prognosis for retaining globe
◦ Reasonable (most owners prefer blind eye to no eye)
◦ Other complications: lagophthalmos, neurotrophic keratitis, dry eye, permanent strabismus…
What clinical signs are associated to retrobulbar abscesses? How are they diagnosed? How are they treated?
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Clinical signs
◦ Acute onset
◦ Unilateral
◦ Exophthalmos (proptosis)
◦ Pain, especially on opening the mouth
◦ Third eyelid protrusion and swelling
◦ Ocular discharge
◦ Pyrexia, lethargy
Diagnosis
* Ultrasound: look for fluid-filled cavity
* Look in mouth (recall close proximity of upper dental arcade to soft tissue floor of orbit)
Treatment
* 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
* Release pus…
- Pressure around and traction on optic nerve can cause temporary blindness and, if not treated urgently, permanent blindness
- Medical management
◦ Systemic NSAIDS
◦ Systemic antibiotics
◦ May need IV fluids and injectable medications if not eating
◦ Topical lubricants until normal blinking returns
What clinical signs are associated with acute glaucoma? When is glaucoma an emergency? How are they diagnosed? How are they treated?
Clinical signs
* Ocular pain (classic triad):
◦ Blepharospasm
◦ Increased lacrimation
◦ Photophobia
* Head shy, yelping, dull/quiet
* Vision loss
* Change in appearance…
When is glaucoma an emergency?
* Two groups of dogs predisposed to acute glaucoma:
* Purebreed dogs with hereditary primary glaucoma (Spaniels, retrievers, Bassets, huskies…)
* Terrier breeds with acute lens luxation and secondary glaucoma
* How to differentiate?
◦ Is it a predisposed breed?
◦ Can you see an underlying cause? (Uveitis, lens luxation)
Diagnosis
Tonometry: measure IOP
* Normal range in dogs and cats:
◦ 10-25mmHg
* Acute glaucoma:
◦ Often >40mmHg
◦ May see IOPs of 60-80mmHg
Treatment
* Reduce IOP – 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
◦ Consider referral assessment of other eye
What are causes of anterior lens luxation? What clinical signs are associated? How is it treated and managed?
- Causes of lens luxation:
◦ Primary: hereditary weakness in lens zonules – terrier breeds predisposed
◦ Secondary: may follow glaucoma, uveitis, cataract - Lens may move anteriorly or posteriorly – anterior lens luxation is a ophthalmic emergency
Clinical signs
* Acutely painful eye
* Glaucoma (episcleral injection, raised IOP, diffuse oedema, vision loss)
* Focal corneal oedema
* Lens outline may be visible in anterior chamber
Treatment
* Offer referral: emergency surgical removal of lens or “couching” to push lens backwards
* Analgesia e.g. oral NSAID and opioid
Ongoing management
* Bilateral condition: contralateral eye likely to be affected but at an earlier stage i.e. subluxation
◦ Consider referral assessment/prophylactic treatment
◦ If eye is enucleated, send for histopathology
How can you differentiate anterior lens luxation from primary glaucoma?
- Is it a predisposed breed?
- If a terrier, assume anterior lens luxation until proven otherwise!
◦ beware the terrier with the acutely painful eye - Does the dog have a history of either problem?
- If very cloudy
◦ Take a photo with a flash
◦ Consider ultrasound - Look at the other eye for clues – bilateral condition
What are examples of corneal emergencies?
- Chemical injury
- FB
- Melting ulcer
- Severe lacerations
How would you treat chemical injuries to the cornea?
- IMMEDIATE irrigation of ocular surface
- If at home, tap water is fine
- Tap water or saline or Hartmann’s solution if animal in the practice
- Flush copiously e.g. 500ml to 1 litre until pH normal (7.5); sedation likely to be necessary
- Test pH of conjunctival sac to determine nature of chemical e.g. urine dipstick
- Early specialist advice
- Medical management for corneal ulceration
- Alkalis may induce ‘melting’ or liquefactive necrosis, intensive medical management indicated
When are corneal FBs an emergency?
If large or painful
What complex corneal ulcers require urgent treatment?
- Deep corneal ulcers
- Descemetocoeles
- Perforated corneal ulcer +/- iris prolapse
- ‘Melting’ ulcer is however a greater emergency
What clinical signs are associated with melting corneal ulcers?
- Lots of gelatinous “gloopy” discharge
- Ill-defined, rounded, soft edges – like melting butter/candle wax…
- Marked corneal oedema
- Marked anterior uveitis (pain, miosis, hypopyon, low IOP)
- Can progress rapidly and perforate within hours
What are 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
