Cornea Flashcards
What does the epithelium originate from (embryology)?
Surface ectoderm
Where does the cornea get its nutrition from?
Aqueous humour
Limbal blood vessels
Where does the cornea get its oxygen from?
Tear film
What does the corneal endothelium and stroma originate from?
Mesenchymal neural crest cells
What are the 3 layers of the tear film and where do they come from?
Lipid- meibomian gland (decreases evaporation)
Aqueous- lacrimal gland
Mucin- conjunctival goblet cells (spread)
How many layers is the epithelium? (X-x)
5-7 layers
What cells form the basal layer of the epithelium?
What is it adhered to?
What cells join the basal cells together?
columnar cells
adhered to the basement membrane
Desmosomes, hemidesmosomes, gap junctions
What cells form the intermediate layer of the epithelium?
What are these cells attached to each other by and to superficial cells?
Interdigitating wing cells
2-3 layers
Desmosomes and gap junctions
What cells make up the top layer of the epithelium?
What joins the cells?
What is on top of these cells?
Flattened squames
3-4 layers
Desmosomes and tight junctions
Microvilli and microplicae
What % of the cornea does the stroma account for?
90%
What is the main component of stroma?
Collagen
What cell allows maintenance of the stroma?
What enzyme does it produce?
Keratocytes
Proteases
What is the basement membrane of the stroma called?
Where is it secreted from?
Descemet’s membrane
Corneal endothelium
How many layers thick is the endothelium?
Single layer
When an epithelial defect occurs what does the epithelium do?
Cells flatten, spread and move across the defect
Where do superficial corneal blood vessels come from (thin wiggly - trees)?
Conjunctiva
Where do deep corneal blood vessels come from (straight short hedges)?
Limbus
What breeds are most affected by pannus/chronic superficial keratitis?
What age?
GSD
Collie
Greyhound
Lurcher
3-5yo
What are the clinical signs of pannus/chronic superficial keratitis?
Which areas are affected?
Uni/bilateral?
Red eyes
Vascularisation, infiltration, pigmentation starting at the Ventrolateral limbus
Cornea, conjunctiva, third eyelid affected
Bilateral
Ulceration is common or rare in pannus/chronic superficial keratitis?
Rare
How do you diagnose pannus/chronic superficial keratitis?
What is the main result?
What is the treatment for pannus/chronic superficial keratitis?
Biopsy
Plasma cells
Topical steroids/ciclosporin or both together
Often need repeat courses
What time of year is pannus worst? Why?
Summer - triggered by UV light
What condition is this likely to be in a cat?
What are the clinical signs? Where?
What age?
Eosinophilic keratoconjunctivitis
White and pink deposits (cottage cheese!)
Superficial corneal stroma and epithelium, conjunctiva
Young/ Middle Aged
How do you diagnose eosinophilic keratoconjunctivitis?
What’s the result?
Treatment?
Cytology (scrapings/biopsy)
Mast cells and eosinophils (with some mixed inflam cells)
Topical steroids/ ciclosporin
(Oral preds If topical not poss)
What are the clinical signs of superficial punctate keratitis?
Which breeds are predisposed?
Multiple fluoro positive corneal opacities (white)
Shetland sheepdogs
Min LH daschunds
What is this likely to be (dog)? Single/multiple raised lesion dorsolateral limbus
What is the treatment?
Nodular granulomatous episcleritis
Topical +/- immunosuppression
Limbal/ epibulbar melanoma are common in what type of dogs?
Treatment?
Darkly pigmented dogs;
Labs
GSD
Excise +/- adjunctive therapy
What could be the cause of corneal lipidosis?
Just inherited Primary hyperlipidaemia DM HyperA Hypothyroidism
Does corneal lipidosis cause inflammation?
Bilateral/ uni?
Location?
No
Bilateral
Subepithelial, central/para central
How is Lipid keratopathy different to lipid dystrophy?
Treatment?
Lipid keratopathy has inflammation and blood vessels
Treat cause of hyperlipidaemia, can do keratectomy/ laser but do this after plasma lipidaemia stable!
Which causes with which?
Larger lipoproteins (triglyceride rich) Smaller lipoproteins (cholesterol rich) Causes… Lipid keratopathy Arcus lipoides corneae
Larger lipoproteins (triglyceride rich) cause Arcus lipoides corneae
Smaller lipoproteins (cholesterol rich) Causes Lipid keratopathy
PDT can cause what type of corneal opacity?
Calcification
What is the breed predilection for dermoids?
GSD
St Bernard’s
What is the purpose of thermal keratopasty in endothelial dystrophy?
How does it do this?
Preventing corneal ulceration.
Post operative fibrosis of the corneal stroma squeezes fluid out and prevents further fluid entry.
Which breed of cat is stromal dystrophy found in?
Uni/ bilateral?
Manx cat
Bilateral
Which breed is macular corneal dystrophy seen in?
What age?
What are the clinical signs?
What test can be done?
Cause?
Lab
Middle aged (~5yo)
Stromal opacity +/- vascularisation
DNA - carbohydrate sulfotransferase 6
Accumulation of glycosaminoglycan
What is the treatment for epithelial inclusion cyst?
Surgical excision
What is the treatment for stromal keratitis in cats with FHV?
Antivirals + steroids
What appearance on the cornea does mycotic keratitis have?
White (icing sugar) appearance
Within what time should an uncomplicated ulcer heal?
7days
How long should you use a diamond burr on a SCCED for?
45-60secs
What enzymes cause the stroma digested causing a melting ulcer?
What are these enzymes produced by?
Proteases and collagenases
Pathogenic organisms, inflammatory cells, resident corneal cells
What is the purpose of corneal cross linking?
Stabilise and sterilise the cornea
Describe these 3 layers of the epithelium?
Top- squamous cells
Middle - intermediate wing cells
Bottom- Columnar cells (regenerating)
What is this?
What part of the eye has to be defected for this to occur?
Corneal hydrops
Descemets membrane
What cells have to be damaged for oedema to enter cornea?
Epithelial cells
Endothelial cells
What are white/tan precipitates In the eye?
What do they indicate?
Where do they stick to?
Keratic precipitates
Uveitis
Endothelium
What age do calcium deposits occur?
Pain?
Treatment?
Elderly patients
Variable comfort
EDTA
What can treat corneal pigmentation?
Topical steroids/ ciclosporin/ tacrolimus
What is this (not pigmented third eyelid)?
What is the treatment?
Punctate keratitis
Topics Steroids
Nodular granulomatous episclerokeratitis
Where in the eye?
Treatment?
Dorso lateral limbus
Topical +/- immunosuppression
What is this likely to be?
What can predispose this?
Squamous cell carcinoma
Chronic keratitis
Lipid (Crystalline stromal) dystrophy
Age of dogs?
Where in the eye?
Inflammation?
Treatment?
Young dogs
Central/ para central
No signs of inflammation
Nothing unless abnormality in bloods then treat that!
Where is lipid deposited in lipid keratopathy?
Stroma
Arcus lipoides
Uni/ bilateral?
Associated with?
Vascularisation?
Bilateral
Hyperlipidaemia (always), triglycerides
Variable vascularisation
Treatment of endothelial dystrophy?
NaCl
Thermal keratoplasty
Partial gunderson flaps
Which vaccine is this associated with?
Pathophysiology
Treatment?
Adenovirus
Type III immunoresponse, antigen antibody deposition on the endothelium
Pred forte QID
NSAIDs
What topical treatment is used for fungal infection?
Voriconizole
Clotrimazole
What are the signs to look for for an ulcer that will possibly melt?
Brachycephalic
More oedema than would expect
Punctate ulcer
360’ vascularisation
What drops do you use in corneal cross linking?
What does it do?
Riboflavin - vit b2
Stabilises cornea and sterilises
What is the lamina fusca?
Transition zone between sclera and outer choroid and ciliary body
What is the lamina cribrosa?
where the optic nerve leaves the globe
Nodular granulomatous episclerokeratoconjunctivitis
Where?
Cause?
What do they cause?
Dorso lateral limbus
Immune mediated
Raised area
