Test 2: lecture 27+28 cornea Flashcards
descemet’s membrane
above the endothelial cell layer of cornea
layers of the cornea
epithelial layer 6-15 layers
stroma- collagen avascular
descemet’s membrane
single endothelial cell layer
how does cornea get nutrition
front from: aqueous layer of tears
edothelial cell layer from: anterior chamber- aqueous humor
function of the cornea
refraction of light
main barrier to penetration by mirco-organisms
conjunctiva hyperemia
episcleral congestion
conjunctiva clear membrane over sclera, then episcleral membrane, then sclera
why is cornea clear
avascular
regularly arranged collagen
relatively dehydrated: Na/K pumps in the internal endothelial layer, that pumps H20 out
corneal edema
what causes this
corneal edema
corneal epithelium or endothelium becomes damaged and there is a build up of fluid inside the cornea
bluish- cobblestoned
endothelial disease: diffuse
epithelial- focal/corneal ulcer
diffuse blue eyes means
endothelial disease leading to edema in the cornea
distemper
damage to what layer of the cornea will lead to focal/corneal ulcers
epithelial (outer layer)
3 causes of endothelial disease of the cornea
breed related endothelial dystrophy
* spontaneous, progressive
* Boston
age-related endothelial degeneration
* common
secondary/intraocular disease
* uveitis
* glaucoma
disruption of Na/K pump- makes blue eyes- edema of cornea
bullous keratopathy
progressive cornea edema that leads to bulla/blister formation and corneal ulcer
can treat with Na/Cl solution
how to treat bullous kertopathy
Na/Cl soultion
thermokeratoplasy- burn cornea to form scar that prevents fluid from coming into cornea
progressive edema- blisters that lead to corneal ulcers
acute bullous keratopathy in cats
can happen suddenly/over night
emergency- can lead to corneal rupture
systemic cyclosporine appears to be a risk factor- may be from descemet’s membrane damage
treat by forcing eye closed for a few weeks
corneal ulcers is caused by loss of —
epithelium +/- stroma
descemetocele
damage of cornea down to descemet’s membrane, then pressure of eye pushes membrane up forming bubble- needs surgery ASAP
superficial ulcers heal by
rapid epithelialization
5-7 days
what causes melting?
collagenases
deep ulcers require vascularization and collagen deposition
collagenases are used during wound healing to reform collagen layers- bacteria can cause over activaity of collagenases that then “melt/eat” the eye
can you use pred on corneal ulcer?
no!
it will cause increased collagenase activity → melting of cornea
what are the “little trees”
blood vessels form to try to heal corneal ulcer
take 3-5 days to form, grow 1mm/day
never go away but blood leaves once healing is done
initial treatment of superficial corneal ulcer
remove underlying cause: eyelash, thorn ect
give ecollar to prevent rubbing
antibiotics- 3-4 x a day
there are no pain meds for eye!
* can use atropine to stop spasms but will dilate pupil for long periods
Can’t use steroids- will cause worse problems
1st step to treat infected ulcer
take cytology
culture
use Q 2 hr fluoroquinolones
what can help with corneal melting?
anti-collagenase
serum: has antiprotease/anticollagenases in it
give every 2-4 hours
prognosis of complicated corneal ulcer
can take 3 weeks to heal
initial 48 hours checks, if ulcer is improving/not getting any deeper can wait and let eye heal
if not improving, may need surgery
when to consider surgery on corneal ulcer
greater then 80% deep
descemetocele
corneal perforation
not getting better with medial treatment
surgery to fix deep ulcers
conjunctival graft
tectonic support- promotes healing and fibroblasts
indolent corneal ulcer are
superficial uninfected corneal ulcer that does not heal in appropriate time
epithelilal cells are damaged for some reason
boxers- SCCED, feline herpes
how to treat indolent corneal ulcer
debride/ scratch off epithelial layer and let eye try to make new layer better
promotes epithelialization, vascularization
can use qtip of diamond butt debridement
why do contacts help with healing
protect new epithelial layer from being rubbed away when blinking
pannus
chronic superficial keratitis cause by UV damage
usually starts ventralateraly and moves progressively inwars
common in german shepherd
— starts ventrolaterally and is a progressive chronic superficial keratitis caused by —
pannus
UV light/ immune mediated?
common in german shepherd
how to treat pannus
steroids, tacrolimus
often managed not cured- can lead to blindness
— is similar to pannus in cats
eosinophilic keratitis
proliferation with eosinophil and mast cells
can be caused by feline herpes
what kind of cells in pannus vs eosinophilic keratitis
pannus: dogs: plasma cells
eosinophilic keratitis: cats: eosinophils and mast cells
how to treat eosinophilic keratitis
steroids and antivirals
steroids can risk making underlying feline herpes virus worse
managed, rarely cured
cat/horse eye- pink/white raised plaques in ventral/lateral eye
corneal pigmentation- melanin deposition
non- specific response to inflammation dogs
pugs and pekingese
how to treat corneal pigmentation
melanin deposition is in response to inflammation
try to remove cause of inflammation
increase lubrication
can suture eyelid mostly closed in pugs to allow eyelids to blink- increase protection of cornea
what can cause corneal sequestrum
cats
breed specific: himalyains
feline herpes
corneal ulcer
entropion
corneal debridement
change in color from corneal necrosis. NOT the same as corneal pigmentation in dogs which in mealnin deposition
corneal sequestrum-
change in color from corneal necrosis. NOT the same as corneal pigmentation in dogs which in mealnin deposition
can be caused in certain breeds or from herpes, chronic corneal ulcer, entropion, or corneal debridement
treat: keratectomy +/- graft
how to treat corneal sequestrum
happens in cats
cut out necrosis- keratectomy +/- graft
white crystalline is caused by —
corneal mineralization
lipid or calcium
from systemic disease (high fat) or topical corticosteroids
treat: underlying cause, stop steroids
corneal dystrophy
bilateral slow progression
heritable- husky 4-6 years old
usually lipid, not painful, no treatment
how to treat corneal dystrophy
no treatment
not painful
bilateral slow progression, heritable (husky)- round white lipid accumultion in the eye
— is deposition of calicum into cornea after chronic corneal disease
corneal degeneration
common in old dogs
+/- vascularization
can be painful, recurrent corneal ulcers
treat: lubricant, keratectomy
how to treat corneal degeneration
topical lubricant
keratectomy
calcium deposition from chronic corneal disease → painful
episcleritis
nodular
+/- pain
immune mediated: cocker spaniels
treat: steroid and doxy
episcleritis occurs in
cocker spaniels
immune mediated?
nodular +/- painful
treat: steroid and doxy
how to treat episcleritis
topical immunosuppression
oral doxycycline; corticocsteroids
nodular +/- painful, immune mediated- cocker spaniels
five-year old DSH
24-hour history of a painful, wet left eye
STT: 15 OU
fluroscein positive OS
PLR present OU
anisocoria OS< OD (left pupil smaller then right)
list two possible causes for the fluorescein uptake in the left eye
what is your initial treatment plan? what is the prognosis?
corneal ulcer or herpes
treat with lubricant and antibiotic, e-collar
anti viral
wait- depending on how deep, check in 48 hours if stable let heal for 7-10 days
good if superifical, poor if deep and doesnt heal well
herpes life long disease
