Ophthalmology Flashcards
what is the outmost layer of the eye?
sclera
what is the function of the sclera?
fibrous capsule that maintains the eyes shape
what structure is found on the dorsal surface of the iris?
granula iridica
what is the blue/grey structure found on the medial and lateral aspect of the eye?
pectinate ligament attachment
what dyes can be used for eye examination?
fluorescein
rose bengal
what is a pupil dilator called?
midriatic drug
what midriatic drug is commonly used for eye examination?
tropicamide
what should the lens of an ophthalmiscope be set to for distant direct ophthalmoscopy?
0
what is the disadvantage of using a direct ophthalmoscope to examine the retina?
only shows a tiny portion of it - have to map retina in your head
what is a slit lamp used for?
highlights the areas of refraction, can help to localise where lesions are by where they are in relation to the refracted areas (find depth of lesions)
what are the areas of the eye where light is refracted?
cornea
front of lens
back of lens
what is assessed first on an optic exam which would determine eye pain?
drooping/change of eyelid from the front of the horse
before sedating the horse what part of the eye exam should be done?
ocular reflexes
what ocular reflexes are performed as part of an eye examination?
PLR
dazzle
menace response
palpebral reflex
corneal reflex
where is the opening of the nasolacrimal duct in horses?
floor of the nose (roof in donkeys) - can see and catheterise
what nerve block is used for the eye examination?
auriculopalpebral
(frontal for sensory)
what is the use of fluorescein for the examination of the eye?
stains the corneal stroma - so identifies epithelial damage
how will fluorescein highlight different types of ulcers?
superficial - sharp edges with no epithelial under-run
indolent - epithelial under-run
deep stromal - intense staining with stain migration
descematocele - intense staining of walls with migration
what are the types of eye ulcer?
superficial, indolent, deep stroll, descematocele
what is a seidal test?
to assess the depth of injuries to the eye for example thorns (will create a river if aqueous humour is coming out)
what is rose bengal stain used for?
assess tear film quality
assess margins of conjunctival/corneal neoplaisia
fungal ulcers
what is the main issue seen with tear quality?
poor quality/quantity of mucoid layer so tear doesn’t stick to the eye
what is the best tool to sample the eye for cytology?
cytology brush (cervical smear swabs)
why should atropine not be used to dilate the pupil for eye examination?
last too long - remain dilated for 6 weeks
what is tonometry used for?
measure pressure in the eye
is upper or lower eyelid laceration better for the horse?
lower (better prognosis) - spreads less of the tear film
how much debridement do eyelid lacerations need?
minimal - very good blood supply
is a medial or lateral eyelid laceration better for the horse?
lateral (better prognosis) - tear ducts found medially
why are sarcoids around the eye problematic?
difficult to surgically remove due to eyelid
creams can be damaging to eye of they get in
what is the most common neoplasia seen on the third eyelid?
squamous cell carcinomas
how are masses on an eyelid removed?
cut out mass and continue excision downwards to then pull skin below it up to make a new eyelid
what are the layers of the cornea?
epithelium
stroma
descemet membrane
endothelium
what are the clinical signs of ulcerative keratitis?
pain
blepharospasm
epiphora
photophobia
why is ulcerative keratitis common in horses?
eyes in prominent position on side of head (stick out)
what is a superficial ulcer?
just epithelium damaged but stroma is intact
what is done to treat superficial ulcers?
topical antimicrobial to prevent secondary infection
(heal well with no complications/scars)
what is a deeper ulcer?
epithelium damaged and some of the stroma
what is done to treat a deeper ulcer?
topical antimicrobials
(heal well but tend to scar)
what is keratomalacia also known as?
melting ulcer
what causes a melting ulcer?
activation/production of proteolytic enzymes by corneal epithelial cells, leucocytes or microbial organisms
what therapy can be used for keratomalacia (melting ulcers)?
topical serum
topical EDTA
topical acetylcysteine
topical tetracycline
systemic NSAIDs
what its a descemetocele ulcer?
epithelium and stroma destroyed down to the descemet membrane
why is a descemetocele ulcer such an emergency?
eye at risk of burst - very thin layer holding it together
how are descemetocele ulcers treated medically?
aggressive use of the following…
topical serum
topical EDTA
topical acetylcysteine
topical tetracycline
systemic NSAIDs
how can descemetocele ulcer be treated surgically?
conjunctival flap
if there is a full thickness corneal laceration what can happen?
iris prolapse (plugs hole)
eye empties
what is the prognosis for full thickness corneal laceration?
good if treated before secondary infection occurs
how can stroll abscesses be treated?
medical - antimicrobial therapy
surgical - deride and corneal graft
how are superficial stroll abscesses treated?
debride epithelium and drain
what causes viral keratitis?
equine herpes virus 2
what is used to treat viral keratitis?
topical idoxuridine
topical trifluorothymidine
topical aciclovir (this is best)
should corticosteroids be used for viral keratitis?
try treat without it as it makes recurrences more likely
how common is fungal keratitis seen in the UK?
rare (common in US)
how fast do fungal keratitis cases resolve?
very slowly
how is fungal keratitis treated?
takes weeks of therapy (enucleation quicker)
antifungals (get worse before better) - voriconazole
how would the onset of immune mediated keratopathies be described?
insidious
how are immune mediated keratopathies treated medically?
topical corticosteriods
cyclosporine A
doxycycline
what is uveitis?
inflammation of uvea (iris, ciliary body, choroid)
what makes up the uvea of the eye?
iris
ciliary body
choroid
how can uveitis be categorised?
posterior or anterior
acute or equine recurrent uveitis (ERU)
what are the three forms of equine recurrent uveitis?
active
quiescent (dormant)
insidious (wax/wane)
what is a major component of uveitis?
it is immune mediated
what are the clinical signs of anterior uveitis?
pain - blepharospasm and epiphora
chemosis (red eye)
constricted pupil
aqueous flare - milky appearance of anterior chamber
blood (hyphaema), pus (hypopyon) or fibrin in anterior chamber
what are the clinical signs of posterior uveitis?
variable pain (often mild)
vitritis
retinal changes
(subtle)
how is uveitis treated if there is no ulcer present?
topical corticosteroids
topical atropine
how is uveitis treated if there is an ulcer present?
topical NSAIDs
topical atropine
how long is uveitis treated for?
treat until normal and then for a further 6 weeks
what are some surgical treatment options for uveitis?
suprachoroidal cyclosporine implant
pars plana vitrectomy
enucleation
what are some possible long term complications of uveitis?
atrophy granula iridica
synechiae
cataracts
glaucoma
retinal pathology
blindness
phthisis bulbi
what is synechiae?
iris sticks to things (usually the lens)
what is a cataract?
any opacity of the lens
how are cataracts diagnosed?
retroillumination (opacities appear dark)
direct focal illumination (transillumination) - cataracts appear white
what are the types of cataracts in horses?
capsular
nuclear
perinuclear (cortical)
equatorial
sutural
complete
how can cataracts be treated medically?
they can’t be - can treat underlying condition if there is one
what age can catarac surgery be performed?
ideally very young - before 4 months old (complications in adult)
what surgery is carried out to treat cataracts?
phacoemulsification
why is glaucoma uncommon in horses?
high pain threshold
not looked for in horses
two drainage options for aqueous humour
what are the clinical signs of glaucoma?
hydrophthalmos/buphthalmos (increase in size)
corneal oedema
corneal striae (membrane tears)
lens luxation
blindness
what colour does a oedematous cornea present as?
blue
how can glaucoma be treated medically?
carbonic anhydrase inhibitor
beta blockers - timolol
NSAIDs/corticosteroids
what carbonic anhydrase inhibitor is used for glaucoma?
dorzolamide (topical)
what are some surgical treatment options for glaucoma?
laser destruction of ciliary bodies
aqueous shunts
enucleation
how good is the blood supply to the fundus of horses?
paurangiotic (poor) - absent at 6 o’clock
what shape is the optic nerve on the fundus?
oval (round in foals)
what colour is the optic nerve on the fundus?
salmon-pink
what are the sections of the tapetal fundus?
neurosensory retina
retinal pigmented epithelium
tapetum
choroid
sclera
