Glaucoma Flashcards
what does the aqueous humor do?
provides glucose and other substances to avascular lens and posterior cornea
removes metabolites and toxins
how can you alter the uveoscleral pathway?
pharmacologically
what structures of the eye can elevated intra-ocular pressure damage?
lamina cribosa/optic nerve
retina
corneal epithelium
iris vasculature/nerves
what are key examination findings with glaucoma?
scleral injection
corneal edema
dilated pupil
what are some signs of chronicity?
buphthalmia
haab’s striae
optic nerve changes
is primary or secondary glaucoma more common?
secondary
which animals should you suspect secondary glaucoma in?
cat
very young or old dog
wrong breed
what causes secondary glaucoma?
something blocks the drainage angle or trabecular network
something blocks the pupil
how do carbonic anhydrase inhibitors work?
decreasing aqueous production
how do beta blockers work?
by decreasing aqueous humor production
when should you not use mannitol?
significant heart disease
kidney disease
what is a surgical procedure that enhances outflow?
shunt or valve with flexible tubing into anterior chamber
what is the proper definition of glaucoma?
a group of diseases that lead to ganglion cell death and axon loss
what produces aqueous humor?
nonpigmented ciliary epithelium
what is the conventional outflow pathway of aqueous humor?
through pupil to iridocorneal angle
pectinate ligaments, trabecular network
aqueous collector channels
episcleral veins
what can you use to measure intra-ocular pressure?
tonopen
tonovet
what difference in IOP between eyes may be significant?
> 5-6 mmHg
what in the eye should you look at for signs of underlying disease?
flare
position and clarity of lens
what is primary glaucoma?
no overt underlying ocular disease
what is primary glaucoma usually from?
breed-related in dogs
uncommon in cats and other species
what type of glaucoma is most common in dogs?
angle closure glaucoma
will most dogs with glaucoma get it in both eyes?
yes, not at same time
what dog breeds are commonly affected by primary glaucoma?
cocker
basset
husky
samoyed
beagle
chow chow
shar pei
shih tzu
shiba inu
how can cataracts cause secondary glaucoma?
lens-induced uveitis
phacomorphic glaucoma: swollen lens
following cataract surgery
what do you need to distinguish with lens luxation/instability secondary glaucoma?
lens subluxation due to buphthalmia
how can neoplasia cause secondary glaucoma?
infiltration or compression of angle
hemorrhage from tumor
uveitis
what are globe/vision-sparing surgical management options for glaucoma?
shunt/valve placement
laser ablations
what are some carbonic anhydrase inhibitors?
dorzolamide/truspot
brinzolamide/azopt
oral: methazolamide
when should you use an oral carbonic anhydrase inhibitor?
cannot medicate any other way
can cause systemic disturbances
what are the most potent option in dogs for glaucoma?
prostaglandin analogues
how do prostaglandin analogues work?
increasing unconventional (uveoscleral) outflow
why should you be sure that you know the lens is not anteriorly luxated in dogs you prescribe prostaglandin analogues?
cause marked miosis in dogs
what is a prostaglandin analogue?
latanoprost/xalatan
do beta blockers work well in dogs with glaucoma?
not really
what is there potential for with beta blockers?
significant systemic absorption
brady cardia, bronchoconstriction
when might you use osmotics for glaucoma?
emergent treatment of acute glaucoma
what is the dose of mannitol?
0.5-2 grams per kg
what should you do for the good eye?
dorzolamide q12h as prophylaxis
check IOP q2-3months
what surgery is performed to decrease aqueous production?
diode or other pigment-targeting laser used to ablate ciliary epithelium
