Lecture 9: Equine Ophthalmology Flashcards
Horses visual field is __degrees
350
Retina contains rods and cones in a __ ratio
9:1
rods sensitive to __light and ___
dim light, motion detection (night vision)
cones sensitive to ___, responsible for __vision
bright light, color vision
what colors do horses see
blue, green, yellow
define Epiphora
tearing (pain)
define blepharospasm
squinting (pain)
foals less than __weeks do not have menace
2-3 weeks
what CN do PLR test
2 and 3
what CN do you test for palpebral reflex
5 and 7
what CN do you test with menace
2 and 7
what CN do you test with dazzle
2,3, and 7
Identify 1-3
- Tapetum
- Non-tapetum
- Optic disk
what are the black dots that arrow pointing to
stars of Winslow
what IV sedation used for eye exam and what dose
xylazine at 150-250mg for 1000lb horse
what blocks are used on eye and what do they block
auriculopalpebral- motor to orbicularis oculi
Supraorbital nerve- sensory to medial 2/3 upper eyelid
Identify blocks 1-2
- Auriculopalpebral
- Supraorbital
what diagnostic test do you do on every horse, every time with eye problem
fluorescence stain
fluorescein stain adheres to __
corneal abrasions
Schirmer tear test must be done prior to ___ and ___
any medications in the eye, prior to sedation with alpha-2 that increase lacrimation
when is the schirmer tear test indicated
Chronic ulcerations or dry cornea
<__mm on schirmer tear test is deficient
10
what is normal IOP
16-30mmHg
consistently high IOP indicates __
glaucoma
consistently low IOP indicates __
inflammation/uveitis
IOP should be performed __ with normal head position after ___ application
unsedated, proparacaine
when should you test IOP
chronic eye problems, corneal edema, buphthalmos
Rose bengal retention indicates a defect in ___
mucin layer of the tear film
__ulcers at very early stages may be negative to fluorescein but positive to rose bengal
fungal
when should you do rose bengal test
chronic eye problems, especially with deficient schirmer
when doing nasolacrimal flush maximum of __cc per side otherwise can cause bleeding
20cc
what do you use to dilate the eye. How long to dilate and how long last
tropicamide 1%, 20 minutes to dilate, lasts 8-12hrs
you should get corneal ulcer culture prior to any ___in eye
medications, including proparacaine
what do you use for corneal culture
cotton swab
how is corneal swab diagnostic and therapeutic
debriefs necrotic debris off ulcer allowing it to heal more rapidly
what do you examine with ultrasound of eye
cornea, lens, retina, iris, ciliary body, corpora nigra, optic nerve, and peri orbital structures
normal or abnormal eye ultrasound
normal
normal or abnormal eye- what wrong
Thickened lens- sclerosis
Detached retina
normal or abnormal eye- what wrong
Cataract
in what scenarios do you want to refer eye for diagnostic procedures
tonopen, slit lamp, electroretinogram, CT, MRI
what wrong
superficial ulcer
what wrong
melting ulcer
what wrong
abscess
what wrong
keratitis
what wrong
viral keratitis
t or f: ulcerations should be treated aggressively no matter how mild
true
what is typical healing time of uncomplicated corneal ulcer
7-10 days
ulcers are considered non healing if it takes longer than __
7-10 days
Tear film proteinases normally ___, what are the two tear film proteinases
detect and remove damaged cells in cornea
Matrix metalloproteinase (MMP) and neutrophil elastase (NE)
bacterial and fungal pathogens upregulate production of ___ which cause further inflammation and degradation of corneal stroma resulting in ___
Matrix metalloproteinase and neutrophil elastase, resulting in melting ulcer
__should be considered likely in every ulcer
infection
what are good topical antibiotics for corneal ulcers
TAO, ciprofloxacin, tobramycin
___is great for beta hemolytic streptococcus corneal ulcers
cefazolin
__ and ___ are good for gentamicin resistant pseudomonas
ciprofloxacin and amikacin
in corneal ulcer treatment, how do you prevent collagenolysis
- serum- antiproteinase activity against MMP and NE
- Acetylcystein 5-10% and EDTA 0.17%
how do you decrease inflammation/uveitis in tx of corneal ulcer tx- how do they work
- Atropine 1%- stabilizes blood-aqueous barrier, reducing protein leakage, stops pain from ciliary muscle spasm, reduce synechiae formation
- NSAIDS: reducing uveal exudation and pain, reduce uveitis
fungi in corneal ulcers have affinity for __
descemets membrane
if you see a deep ulcer what do you need to tx with
anti-fungal
what is tx against fungal ulcer
natamycin, miconazole, itraconazole/DMSO, fluconazole, silver sulfadiazine, voriconazole
which antifungal has best corneal penetration
voriconazole
what medications do you put in sub palpebral lavage line
- Cefazolin
- Tobramycin
- Serum
- Atropine
- Diflucan
if a corneal ulcer fails to heal in 7-10 days what do you do next
Cytology to rule out resistant infection
If a cytology from non-healing ulcer is negative then what is likely the cause
indolent from microscopic hyaline membranes that form on ulcer bed and slow epithelial healing
if you have a clean cytology- what treatment can you do to promote healing
keratectomy/keratotomy debridement
how does debridement promote healing
removing necrotic tissue and microbial detritus speeds healing and minimizes scarring
what are conjunctival grafts used for
management of deep melting ulcer, large corneal ulcers, descemetoceles or perforated corneal ulcers/iris prolapse
how do conjunctival grafts help with healing
supplies immediate blood supply and physically stabilizes the eye
conjunctival grafts with result in permanent ___ that will inhibit __
scarring to cornea that will inhibit vision
What blocks are performed for enucleation
Supraorbital, auriculopalpebral, retrobulbar
describe the enucleation procedure
- Tarsorrhaphy- exenteration includes muscles
- Enucleation of globe alone
- Close skin
full thickness corneal or scleral perforations are associated with ___, __ and ___
iris prolapse, shallow anterior chamber, and hyphema
what is Seidel tests
using large amount of stain can see aqueous humor flowing out of laceration. Gentle pressure on the globe may be required to observe flow
what is tx for corneal lacerations/perforations
- Small lacerations may heal medically
- Large lacerations may require sx
- Traumatic corneal perforation with extension extrusion of intraocular contents should be enucleated
what is a common cause of viral keratitis
EHV-2
what are some signs of viral keratitis caused by EHV-2
epiphora, conjunctivitis, blepharospasm, linear and punctuate corneal opacities
what wrong based on stain uptake
viral keratitis- EHV-2
what is tx for viral keratitis
- Topical NSAIDS- diclofenac, flurbiprofen
- Topical antivirals- valacyclovir, idoxuridine
what is the cause of eosinophilic keratoconjunctivitis
immune mediated from environmental allergens or parasites
what are some signs of eosinophilic keratoconjunctivitis
corneal granulation tissue with predominant eosinophils, blepharospasm, epiphora
what is tx for eosinophilic keratitis
topical steroids, cetirizine
what is ddx for eosinophilic keratoconjunctivitis
SCC
what wrong- lots of eosinophils observed
eosinophilic keratoconjunctivitis
what is immune mediated keratitis
chronic corneal opacity without corneal ulceration or significant uveitis
what are the 4 types of immune mediated keratitis
- Epithelial
- Superficial stroma
- Deep stromal
- Endothelitis
what is tx for immune mediated keratitis
- Cyclosporine
- Topical NSAIDS
what is prognosis for immune mediated keratitis
guarded
A stromal abscess vision threatening sequela to __
corneal ulcer
most stromal abscesses involving descemets membrane are __
fungal
aggressive medical therapy against stromal abscess should improve in 2-3 days, if no response then consider __
sx removal and corneal graft
all painful eyes should be ___
stained with fluorescein
what drugs are contraindicated when ulcer is present
corticosteroids
topical anesthetics should not be used in treatment of corneal uclers as they __. __ is toxic to corneal epithelium
delay epithelial healing, proparacaine
