Lecture 3 Flashcards
what is this
iris atrophy. not a persistent pupillary membrane because it does not originate from the collarette
also a mature cataract in the lens
explain what iris atrophy is
a senile old age loss of iris tissue where the pupillary margin starts to look moth eaten, creating dyscoria (abnormal pupil shape). if it’s severe it can cause PLR deficit
what is this?
iris atrophy, can see the pupil on the right side of the picture and then a bunch of holes and moth eaten appearance. this dog is likely old.
what is this? what treatment is required?
uveal cyst (in the anterior chamber in front of the iris). these are benign and not painful at all
no treatment is required as long as it doesnt affect vision, but you can do a laser ablation or aspirate with a 27G needle if you want
what breeds like to get uveal cysts?
goldens, labs, boston terriers
what is this
hyphema: blood in the anterior chamber
usually just from disease in the eye but can be from systemic disease too
what is this? treatment and prognosis?
hyphema: complete filling of anterior chamber with blood secondary to a globe rupture. this eye has zero prognosis for vision and the eye needs to come out
what are the causes of hyphema?
trauma: intraocular tumors, retinal detachment, anterior uveitis
systemic: leukemia or polycythemia, clotting abnormalities, circulatory disorders (hypertension)
what is this
iris melanoma: multifocal areas of iris hyperpigmentation
the most common primary intraocular tumor in cats is
iris melanoma
does iris melanoma in cats like to spread/metastasize?
no they usually dont spread
if iris melanoma in a cat progresses enough, it can cause…
anterior uveitis, glaucoma, ocular discomfrt and vision loss
how will you treat this cat
iris melanoma
can watch/monitor for changes and measure IOP
can do a laser ablation of the pigmented lesions
take the eye out when glaucoma occurs or if there’s diffuse changes noted
what is this
iris melanoma
what is this? what is the prognosis?
iris melanoma, diffuse pigmentation everywhere on the iris.pigment is also now on the anterior lens capsule and it is “too late” and if the cat doesn’t already have glaucoma it will get it :(
what is buphthalmia?
enlargement of the eye associated with glaucoma
10 yo border collie acutely blind but owners said his eyes have been abormal for a while. he has no menace, dazzle, or PLRs. IOP OD 40 and OS 62. Diagnosis?
glaucoma: elevated IOP with damage to the optic nerve
the aqueous humor is produced by the _____
ciliary body by the non pigmented epithelium
normal IOP is
15 to 25
describe the normal flow of the aqueous humor
produced by the ciliary body then goes into the posterior chamber (between the iris and the lens) and thru the pupil into the anterior chamber. then it flows to the iridocorneal angle (ICA) which is where the base of the iris meets the cornea and sclera.
what are the 2 different ways in which the aqueous humor can flow out of the eye?
conventional outflow: this is how 85% of the aqueous humor exits, flows thru the corneoscleral trabecular meshwork and this is where the majority of the resistance happens. It’s sort of like a seive for the flud, slows it down. it then goes into collecting veins
nonconventional outflow: thru uveoscleral outflow and thru the sclera. this is INDEPENDENT of IOP and is driven by OSMOSIS, then goes into systemic circulation.
he most frequent cause of irreversible blindness in dogs is
glaucoma
true or false: glaucoma can be caused either from increased production of the aqueous humor or a laxck of outflow
FALSE it is only due to decreased outflow, NEVER from over production
what is goniodysgenesis?
a predisposition to glaucoma/primary cause of glaucoma; the normal pectinate ligaments and spaces between them for the aqueous humor to flow through fail to form and the ICA becomes smaller, making it difficult for the aqueous humor to outflow. usually affects both eyes at different times
true or false: the prescence of gondiodysgenesis indicates glacuoma will develop later in life
false! most of the time they do but it’s no ensured
list at least 3 breeds predisposed to gondiodygenesis
atika, shiba inu, chow chow, beagle, husky, dalmation, GSD, etc
true or false: congenital primary causes of glaucoma are rare
truel
list some secondary causes of glaucoma
anterior lens luxation (prevents normal outflow)
anterior uveitis (debris and cells plug everything up)
intraocular neoplasia
hyphema
retinal detachment
true or false: most cases of glacuoma occur chronically
false, most cases occur acutely
glaucoma destroys which cells?
ganglion cells and the optic nerve leading to loss of vision
how quickly can vision be lost in acute cases of glaucoma?
in less than 1 day, necrosis and apoptosis of the ganglion cells in the retina occurs, and by day 7 there will be end stage retinal atrophy
what are the 3 effects of an elevated IOP?
ischemic damage
compressive damage to axons (can be reversible if caught early)
later degeneration: lamina cribosa gets pushed and you get optic nerve cupping, this is irreversible blindness
why does increased IOP cause mydriasis?
axon compression in the retina and optic nerve, ischemic damage to the iris sphincter muscle initially, and chronic atrophy of the iris stroma
why does increased IOP cause corneal edema?
the aqueous humor is pushed into the cornea from pressure, and the endothelial cells alter in function; they are no longer able to pump water out and eventually die off with chronicity
list some chronic changes of elevated IOP
buphthalmia (globe gets stretched from pressure)
Haab’s striae: stretch marks in descemet’s membrane
lens subluxation: globe enlargement causes zonules to stretch, usually a posterior lens luxation when glaucoma is the primary cause