LA Ophthalmology Flashcards
1
Q
what are 4 things to pay attention to when examining large animals?
A
- ocular comfort: eyelash position
-will be pointing down or in if discomfort
-do before sedation - 3rd eyelid: retropulse globe to produce passive prolapse! can take a lot of force
- sedation can decrease IOP
- taking pressures without blocking auriculopalpebral n can result in increased IOP due to strain of pushing eyelids open (in horses)
2
Q
what types of sedation are used for ophtho exam in horses?
A
- xylazine: 0.5-1mg/kg IV
- detomidine: usually only required for badly behaved patients or when extra sedation needed for procedure
-0.02-0.04 mg/kg IV
3
Q
what nerve blocks are used in horse ophthalmic exams?
A
- auriculopalpebral
-palpebral branch of facial nerve; paralyzes orbicularis oculi muscle
-they can still blink just not resist
-sensation to eyelids persists and some palpebral function
-usually palpate along zygomatic arch roughly halfway between the eye and ear, strums like a rubber band
-inject approx 1ml of lidocaine - block various branches of CN V to block sensation to eyelids
-frontal (supraorbital) branch: sensory to upper eyelid
-lacrimal branch: sensory to lateral upper eyelid
-infratrochlear branch: sensory to medial canthus
-zygomatic branch: sensory to lower eyelid
-nasociliary branch: sensory innervation to cornea
4
Q
describe orbital fractures in large animals
A
they happen!
if closed: pop it back in
if open: call a surgeon
4
Q
describe anatomical differences
A
- orbit: laterally on skull
-mononuclear vision enhanced
-horse, sheep, cattle, and goat all have enclosed orbit (completely encompassed by bone) - iris: oval in horizontal plane in oxen, horses, sheep, goats
-granula iridica/corpora nigra present in herbivores: series of black masses on upper edge of pupil (NOT a tumor!) - retinal vessels
-horses paurangiotic
-cows, sheep, goat: holangiotic
5
Q
describe lid lacerations in large animals
A
- COMMON
- do NOT trim tissues!! if you sew it, it WILL heal
- two layer closure required!!
-if only close skin side, conjunctiva will grow across inner portions and it will dehisce
6
Q
describe entropion in large animals
A
- most common neonatal eyelid abnormality
- temporary tacking sutures until grown
7
Q
describe keratitis- superficial, uncomplicated corneal ulcers in large animals
A
- same as in dogs:
-no stromal involvement
-acute onset
-no signs of infection (stromal loss, cellular infiltrate, stromal defects) - treatment:
-topical broad spectrum Abx q6-8 hrs: ofloxacin or neopolybac
-atropine PRN to keep pupil dilated
-systemic NSAIDs if reflex uveitis present (much more common in horses than dogs and cats!)
-NO steroids or topical NSAIDS!
-may consider a prophy antifungal! - if nonhealing/indolent:
-start with cytology!
-never drag needle across horse cornea though horsey eye
8
Q
describe bacterial keratitis in horses
A
- stromal involvement: corneal melting, edema, cellular infiltrate
- anterior uveitis: miosis, flare, hypopyon, hypotony
- treatment:
-broad spectrum Abx: ofofloxacin or moxifloxacin q1-4h
-anti-melt (anti-collagenase): serum, EDTA, N-acetylcysteine, or topical oxytet q1hr
-atropine: as needed to dilate pupil, typically q4-6hr to start, then decrease to q12-24hr
9
Q
describe fungal keratitis in horses
A
- common in horses, esp in SE!!: warm and wet = fungus festival
- most commonly involve aspergillus or fusarium spp.
- clinical appearance:
-progressive, subacute keratitis
-painful
-severe secondary uveitis
-ulcer present for longer than 1-2 weeks
-may have healed but fungus set up shop and caused stromal abscess (fl. neg.)
-love to grow to descemet’s membrane = hard to cut out - treatment: DIFFICULT
-poor prognosis and requires long-term aggressive therapy
-goals: kill fungus, kill bacteria, and control secondary uveitis
-can take 4-8 weeks or more to resolve
-will heal with scarring (bc lost cornea, decreases visual capabilities and calls into question soundness to be ridden)
-subpalpebral lavage needed
-also control melting with topical serum
-control uveitis with oral banamine
-topical atropine too but be careful of slowing gut!! - surgical treatment:
-keratectomy + corneal or conjunctival graft: indicated when there is no response to medical management, formation of deep corneal furrow, or lesion is deep within the cornea
-deep lesions: penetrating keratoplasty, lamellar keratoplasty, or deep lamellar keratoplasty
10
Q
describe stromal abscesses in horses
A
- usually the result of tiny penetrating injury which inoculates corneal stroma with infectious agent; entry subsequently heals but a few weeks later an abscess forms
- diagnosis:
-clinical appearance
-culture and cytology useless as epithelium is intact! - treatment:
-if well vascularized: oral and topical antibiotics/antifungals/atropine
–why we often mix antifungals with DMSO (draw across epi surface)
-if non-vascularized, severe abscess: keratectomy and graft, or penetrating keratoplasty if deep endothelial
11
Q
describe equine recurrent uveitis
A
- major disease of horses; leading cause of blindness
-2-10% prevalence in US - immune-mediated, panuveitis characterized by recurring episodes of intraocular inflammation that develop weeks to months after an initial episode of uveitis
*uveitis is also number 1 cause of cataracts in horses
12
Q
how do you decide that a horse with uveitis has equine recurrent uveitis? (5)
A
- history of repeated episodes of redness (may have been previously diagnosed as allergies)
- signs of chronic inflammation
- signs of inflammation in contralateral eye
- presence of chorioretinal scarring: butterfly scarring
- the only “true” way to diagnose ERU is by documented repeated episodes of uveitis
13
Q
describe clinical signs of ERU
A
- photophobia
- blepharospasm
- corneal edema
- aqueous flare
- hypopyon
- miosis
- vitreous haze
- chorioretinitis
14
Q
describe pathogenesis, diagnosis, and retinal changes of ERU
A
pathogenesis:
1. unknown but several theories: molecular mimicry, bystander activation, epitope spreading
diagnosis:
1. based on presence of characteristic clinical signs
2. history of documented recurrent or persistent episodes of uveitis
retinal changes:
1. peripapillary chorioretinal scars (butterfly lesions)
2. exudative retinal detachments
