Opthalmology Midterm Flashcards
What is the main site of resistance to drug penetration in the eye?
corneal epithelium
What is the maximum volume of subconjuctival injections into the eye for small and large animals?
cat and dog = 0.25 ml
LA = up to 1 ml
Which parts of the eye require systemic administration for treatment?
retina, optic nerve, vitreous
What are the 3 types of miotic agents and what are examples of each?
parasympathomimetic - pilocarpine
anticholinesterase - demecarium bromide
PGF2a analog - latanoprost, travoprost
Which mydriatic agent is cycloplegic and should not be used in glaucoma patients?
atropine
What are the two groups of mydriatic drugs and examples of each?
parasympatholytic - atropine, tropicamide
sympathomimetic - epinephrine, phenylephrine, dipivefrin
What is the MOA of atropine in the eye?
cycloplegic - paralyzes ciliary musculature to decrease intraocular pain
Which ocular drugs can help differentiate scleral injection?
phenylephrine and epinephrine
What is the MOA of adrenergic beta blockers in the eye?
reduce aqueous humor
What is the number one antibiotic that causes conjuctival irritation?
neomycin
What is the drug of choice for mycoplasma and chlamydia conjuctivis in cats?
oral doxycycline
What can doxycycline help with the eye besides being an antibiotic?
stabalizes corneal collegenases - helps with corneal ulcer
What drug can cause retinal degeneration in cats?
enrofloxacin
What is the only approved topical treatment for fungus in the eye?
natamycin
What is the drug of choice for use as a subpalpebral lavage treatment?
voriconazole
What 2 antiviral drugs are NOT used in feline herpes treatment?
acyclovir and vacyclovir
What drug can be used to treat the rare condition, neurogenic KCS?
pilocarpine
What are the 2 drugs of choice to treat KCS?
Cyclosporine A and tacrolimus
What muscles open the eyelid and what are their innervation?
levator palpebrae superioris(CN 3) Mullers muscle (sympathetic)
What muscle closes the eyelid and what innervates it?
orbicularis oculi - CN 7
Term for turning in of the eyelid
entropion
Term for turning out of the eylid
ectropian
Term for distortion of normally positioned lashes so they irritate eye
trichiasis
Term for hair emerging from one or more meibomian gland openigns
distichiasis
Term for hair growing from meibomian gland through plapebral conjuctiva
atypical distichia, ectopic cilia
What is the treatment of choice for distichiasis?
cryotherapy
How is ectopic cilia treated?
partial thickness excision and/or cryoablation
What dog breeds are predisposed to entropion?
shar pei, chow, bulldog, st bernard, golden retreiver
What is the treatment for entropion in puppies less than 5 months of age?
temporary eyelid tacking
What breeds are predisposed to ectropion?
st bernards, spaniels, hounds
What species have T-shaped third eyelids?
ruminants and dogs
Which species has a muscle to the third eyelid?
cat (sympathetic innervation to retract)
What kind of neoplasms occur in the third eyelid?
lymphosarcoma and adenocarcinoma
What breed gets plasma cell infiltration of the third eyelid?
german shepherds
What is the indication for a full thickness eyelid resection in neoplastic eyelid diseases?
when lesion involves less than 1/4 to 1/3 of eyelid margin
What is the best treatment for canine eyelid neoplasms?
cryotherapy
Term for absolute enlargement of globe secondary to chronic glaucoma
buphthalmos
Term for rostral displacement of the globe
exophthalmos
Term for retraction of the globe into the orbit
enophthalmos
Resistance to opening the mouth can indicate what eye disease?
retrobulbar abscess
What are common causes of exopthalmos?
abscess, cellulitis, neoplasia
What are common causes of enophthalmos?
congenital (dolio), phthisis bulbi, microphthalmia
What are common causes of strabismus?
neoplasia, proptosis, congenital (brachy)
What percentage of fibers cross over in the optic chiasm in cats, dogs, horses, sheep, pigs, cows, fish, birds and reptiles?
Cats : 65%
Dogs: 75%
Cows, horses, sheep, pigs: 90%
Fish, birds, reptiles: 100%
What is the afferent nerve for the PLR reflex?
CN 2
Which cranial nerve is motor to the superior oblique muscle?
CN 4
Which CN is motor to lateral rectus and retractor oculi muscles?
CN 6 (abducens)
What CN supplies adrenergic innervation to the cats third eyelid?
CN 6 (abducens)
What Cn is motor to orbicularis oculi muscle and gives parasympathetic innervation to lacrimal gland?
CN 7
What CNs are tested in the palpebral reflex?
5, 6, and brainstem
What CNs are tested in the corneal reflex?
CN 5, 6, and 7
What CNs are tested in the dazzle reflex?
CN 2 and 7 and visual pathway up to before visual cortex
What are Ddx for unilateral miosis?
drugs, horners syndrome, uveitis, posterior synechiae, iris hypoplasia
What are ddx for bilateral miosis?
drugs, uveitis, organophosphate toxicity
What are ddx for unilateral mydriasis?
drugs, CN 3 lesion, iris atrophy, ciliary ganglion lesion, posterior synechiae, optic neuritis, glaucoma, retina problems
What are ddx for bilateral mydriasis?
drugs, fear, death, total retinal atrophy, optic nerve atrophy, retinal detachment
What are the CS of horners syndrome in all species?
miosis, ptosis, elevation of nictating membrane
What are the special CS of horners syndrome in cows and horses?
horses - unilateral sweating
cow - reduced sweating, pinna heat
How can you differentiate between feline herpes conjuctivitis and chlamydia?
herpes - can cause keratitis
chlam - more chemosis
What are the 3 layers of the tear film and what produces them?
lipid - meibomian glands
aqueous - lacrimal gland, third eyelid gland
mucus - goblet cells
What is the medical treatment for KCS?
cyclosporine A, tacrolimus
What is the main cause of KCS?
immune mediated, T cell infiltration of lacrimal tissue
What is the most common cause of horners syndrome in dogs?
lesions of third neuron, postganglionic lesion, idiopathic
What is the surgery treatment for KCS?
medial canthoplasty (brachy breeds)
What layer of the cornea is hydrophobic and lipophilic?
epithelium - barrier to drugs and fluorescin
What is the cornea stroma made of?
75% water, 25% collagen
What nerve innervates the cornea?
CN V (trigeminal)
What is reflex uveitis?
any stimulation of corneal nerves = reflex of CN V to anterior uveal tract (happens with keratitis and corneal ulcers - muscle spasms)
Term for stromal loss but some healing occured and there is still a hole covered with epithelium.
facet
What is the rate of growth of corneal blood vessels and epithelial cells in the cornea?
1 mm/day
What is the rate of WBC migrating in the cornea?
8.6 mm/day
What part of the cornea is hydrophobic?
descemets membrane
What is seidel’s test?
if fluorescein in diluted in a deep ulcer –> aqueous humor leaking out
What is an indolent ulcer?
superficial corneal erosion with epithelial “lips” -fluorescin seeps under the lip
What is the treatment for of canine indolent ulcers?
debridement followed by grid keratotomy or diamond burr debridement
When should grid keratotomys not be done?
complicated ulcers or cats or horses
What is the most common cause of corneal ulcers in cats? Whats the most classic sign?
feline herpesvirus 1
dendritic ulcers
What is the treatment for feline herpesvirus ulcers?
cidofovir (antiviral)
What antiviral is fatal to cats?
acyclovir
What are the different diseases associated with white corneas?
corneal dystrophy, degeneration, fibrosis, descemets striae, keratic precipitates
What disease is descemet’s striae associated with? What does it look like?
glaucoma - membrane breaks leaving linear white scars
What white corneal disease is pathognomic for anterior uveitis?
keratic precipitates - can become brown over time
What is the only blue corneal opacity?
edema
What part of the cornea is a barrier to edema and an active pump?
endothelial layer
What are diffuse corneal edemas a result of?
endothelial dysfunction - glaucoma, uveitis, immune mediated endothelitis, blue eye (CAV 1)
What happens when there is damage to the endothelium of the cornea?
does not undergo mitosis - hypertrophies instead
What is the treatment for corneal edema?
5% saline, 30 mins apart from other meds
thermokeratoplasty - make dots on cornea
keratoleptynnsis - conjuctiva graft