5: cornea - giuliano Flashcards
what are the 4 layer to the cornea? [exterior to interior]
epithelium
stroma
descemet’s membrane
endothelium
which layers of the cornea are hydrophillic?
clin significanc?
stroma
the fluorescein stain is hydrophillic so adheres to the stroma if there is a perforation to the epithelium [corneal ulcer]
what is a corneal ulcer?
exposed stroma - perforated corneal epithelium
what are the functions of the cornea?
- component of fibrous tunic
- main ocular surface barrier - entry of pathogens, penetration of therapeutic agents
t/f
any dec in clarity in the cornea is indicative of pathology
true
why is the cornea clear?
- absence of blood vessels
- deturgescence
- regular arrangement of collagen
- absence of pigment
- relatively acellular
what is deturgescence and how does the cornea achieve and maintain it?
relative dehydration of the cornea
stroma is sandwiched btwn 2 layers that keep the water out - surface layer of epithelium and endothelium
endothelium has active Na/K ATPase pumps that pump water out
what is the order of MDB tests:
STT, fluorescein staining, IOP measurement
what are the 7 deadly corneal colors?
red bule white yellow greasy tan brown black
what do blood vessels tell you about the state of the eye / dz of the eye?
that the dz is due to chronic irritation
how do vessels tell you where the dz is?
superficial: corneal epi dz, fine/branching (tree)
deep: stromal or intraocular dz, NON branching (hedge)
describe conjunctival vessels?
what do they tell you about dz?
superficial, tortorous, branching, move w conj, blance w eip
superficial dz
describe scleral vessels?
what do they tell you about dz?
deeper, straighter, less branching, immobile, blanch slowly w epi,
deep, intra ocular dz
in general, what does hyperemia tell you?
vasodilation is occurring in the eye
what 2 ocular dzz are vision robbing in a matter of 24 hours?
glaucoma
uveitis
what are 2 categories of dz that superficial vessels suggest?
insufficient corneal protection
excessive corneal irritation
what might cause insufficient corneal protection?
lagophthalmos macropalpebral fissure CrN 5 or 7 paralysis ectropion KCS
what might cause excessive corneal irritation?
entropion distichiasis ectopic cilia trichiasis FB lid tumor blepharitis
what types of dzz might be occurring when deep vessels are visible?
deep keratitis
scleritis
uveitis
glaucoma
what does blue cornea indicate?
edema
ddx? diffuse blue color to cornea fluorescein negative marked non painful not inflammed normal IOP flare absent
endothelial degeneration
endothelial dystrophy
monitor for corneal bullae & 2* ulceration
ddx? diffuse blue color to cornea fluorescein negative marked painful inflamed abnormal IOP flare present
glaucoma
uveitis
anterior lens luxation
ddx? focal blue color to cornea fluorescein positive mild/focal painful inflammed
corneal ulceration
what species MC gets infectious keratomalacia?
horses
when dealing with chemicals around eyes, always make sure you use ____ and NEVER ____
solution and NEVER scrub
what does whispy white/grey in the cornea indicate?
scar tissue - disorganization of stromal collagen
when scar tissue is present, what will fluorescein test results be?
negative
t/f
scar tissue is painful for the patient
false
Tx of scar tissue in the cornea?
none!
will remodel very slowly on its own
what does a sparkly white color in the cornea look like?
lipid [cholesterol] or mineral [Ca] deposits
typical presentation of primary dystrophy of the cornea?
bilateral [not necessarily symmetrical]
young dogs [inherited]
what is degenaration vs dystrophy?
degeneration - started normal and deteriorates [often 2* to a problem]
dystrophy - inherited [not necessarily congenital b/c not always present at birth]
what are ddx of a sparkly white cornea?
corneal lipid degeneration
corneal lipid dystrophy
corneal limbal lipid infilatrates
what is corneal lipid degeneration?
often dev 2* to what condition?
lipid and mineral corneal stromal infiltrates that are accompanied by vascularization, scarring and pigmentation
2* to chronic corneal ulceration or non ulcerative keratitis
what is corneal lipid dystrophy?
1* symmetric, bilateral, non inflammatory, inherited corneal opacity that is assoc w lipid infiltrate in the corneal stroma
may affect epi [recurrent erosions], stroma or endo [chronic corneal edema]
characteristic race track appearance of white tissue in cornea
what is corneal limbal lipid infiltrates?
bilateral, limbal associated stromal infiltrates 2* to lipid-laden serum in the limbus
may extend around entire limbus [arcus]
sys hyperlipidosis - look for systemic metabolic abnormalities]
how dies pigment get into the cornea?
carried there by vessels - insoluble, intracellular pigment; grows from limubs
impregnated - ruptured eye [iris shows through], FB
cornea sequestrum - cats, brachycephalics - necrotic cells
pigment laid down in cornea by vessels might be due to what?
insufficient corneal protection [lagophthalmos, macropalpebral fissure, CrN 5 or 7 paralysis, ectropion, KCS]
excessive corneal irritation [entropion, distichiasis, trichiasis, ectopic cilia, FB, lid tumor, blepharitis]
immume mediated [chronic superficial keratitis (pannus)]
what is common loc for pigment deposition in brachycephalics, such as pugs?
why?
nasal deposition
b/c medial lower eyelid entropion is common
what do greasy / tan precipitates in the eye called and what dz do they indicate?
keratic precipitates (KPs)
uveitis (prior or chronic)
“classic” cats w FIP
where do keratic precipitates deposit?
deposit as endothelial plaques
what does yellow/green cornea indicate?
cellular infilatrates => stromal inflammatory cells
what are important r/o for a green/yellow cornea?
bacT keratitis
fungal keratitis
corneal FB
contusion
what diagnostic test is ESSENTIAL for a yellow/green cornea?
culture and sensitivity
cytology
what condition almost always co exists with yellow/green cornea?
uveitis
what causes keratitis AND conjunctivitis?
feline corneal sequestrum
feline eosinophilic keratitis
feline herpes virus
nodular granulomatous episclerokeratoconjunctivitis (NGE)
what is pannus?
chronic superficial keratitis
what is the etiology of pannus?
immune mediated dz of obscure cause
what is common initial presentation of pannus?
begins as reddened plaque at ventrolateral cornea
usually bilateral but NOT always symmetrical
t/f
pannus can progress to involve the entire cornea, eventually resulting in blindness
true
what ocular structure does “atypical” pannus involve?
the 3rd eyelid
risk factors to the development of pannus?
german shepherds and greyhounds
high altitude
solar radiation
tx of pannus?
topical steroids
topical cyclosporine
b-radiation if difficult cases
t/f
pannus is a curable condition
false
it is NOT curable - it is controllable
what is a choristoma?
normal tissue in an abnormal location
consider it a benign tumor
what is a dermoid?
a choriostoma on the eye
what does dermoid cause?
chronic irritation
dec tear production
tx of dermoid?
keratectomy
+/- conjunctival graft
