Ophth - Conditions of cornea and sclera Flashcards
What type of cells make up the cornea?
Transparent stratified squamous cell epithelium and collagen matrix
What is the limbus? What cells make up the limbus?
Transitional zone between cornea and sclera
Stem cells here
What is the sclera?
Fibrous tunic which give globe rigidity
How does the cornea maintain transparency?
Corneal stroma is a collagen matrix maintained in a relatively dehydrated state
Layered collagen with parallel fibres
No pigments
No vessels
Non-keratinised epithelium
How can you examine structural changes on the cornea? How does it work?
Use a slit beam - highlights deviations in depth and flare
What do you use to examine the cornea for exposed corneal stroma?
Fluorescein dye
What is fluorescein dye?
Orange colour
Mildly irritant
It turns green when water bound
It adheres to exposed corneal stroma
Needs flushing out
What are ocular clinical signs of corneal lesions?
Epiphora
Blepharospasm
Conjunctival hyperaemia
Corneal colour change
Anisocoria
What is anisocoria?
Two pupils not the same size - myosis on affected side
Sign of reflex uveitis
What is reflex uveitis?
Spasm of the ciliary body causing miosis - constriction of the pupil
Is painful
When does reflex uveitis occur?
Secondary to anterior ocular pain
How do you treat reflex uveitis?
Mydriatics - atropine
What does a blue corneal opacity mean?
Oedema - the dehydrated state of the cornea is compromised by and epithelial or endothelial defect
What do epithelial defects causing corneal oedema look like? What causes them?
Hazy diffuse, accompanying ulceration
What do endothelial defects causing corneal oedema look like?
Mottled, diffuse blue colour
What are some causes of endothelial defects causing corneal oedema?
Uveitis, glaucoma, lens luxation, geriatric endothelial degeneration (old age)
What are some causes of red corneas?
Vascularisation - superficial or deep neovascularisation
Or haemorrhage
What does superficial neovascularisation look like?
Branching trees of red vessels extending from the bulbar conjunctiva
They DO cross the limbus
What is the purpose of superficial neovascularisation?
Corneal healing - are a sign of a superficial corneal lesion
What does deep neovascularisation look like?
Fine straight non-branching vessels radiating from around the limbus
Arise from the limbus
The DO NOT cross the limbus
What causes deep neovascularisation?
Deep stromal/intraocular cause
What cause white colour change to the cornea?
Corneal fibrosis - a scar
Metabolic infiltrates
Inflammatory cell infiltrates
What is inherited corneal dystrophy?
When lipid or minerals are deposited in the eyes causing bilateral white clouds/arcs in the eyes
What dogs get inherited corneal dystrophy and what is the treatment?
Young dogs
CKCS, husky etc.
Little impact on vision, not treatment necessary
What causes black/brown changes to the cornea?
Pigmentary keratitis - chronic irritation to the cornea
How do you treat/prevent pigmentary keratitis of the cornea?
Lubrication daily, especially in brachys
What causes pink changes to the cornea?
Proliferative cellular infiltrate
What are the clinical signs of proliferative cellular infiltrate?
Superficial vessels
Pigments
Pink tissue in acute phase
White crystalline spots
What is chronic superficial keratitis (‘pannus’)?
Progressive bilateral condition of immune mediated origin causing dark clouding of the cornea in German shepherds and greyhounds
How can you treat chronic superficial keratitis (‘pannus’)?
Can only be controlled
Topical steroids
Immune modulators - cyclosporine (optimmune)
What are the steps of epithelial repair in corneal healing?
Detachment - of the epithelial cells
Movement - cells slide to fill the defect
Proliferation - epithelial cell mitosis thickening the epithelium
Reattachment - to the basement membrane
How long does it take for an uncomplicated superficial epithelial ulcer of the cornea to heal?
1-2 weeks
How does stromal repair of the cornea occur?
Fibroblastic proliferation
Fibres are more disorganised - causes corneal scarring
Remodelling occurs over months to years
How does endothelial repair of the cornea occur?
Cells at the margin of the wound elongate
cells get spread thinner and migrate
No mitosis possible
What is a deep corneal ulcer also called?
A stromal ulcer
What is the name for complete stromal loss?
Descemetocoele
What is a descemetocoele? What does it look like?
Complete stromal loss - the base of the ulcer looks clear into central eye
What is it called when an ulcer occurs without any proceeding signs and is not healing?
Spontaneous chronic corneal epithelial defect (SCCED)
What are the clinical signs for Spontaneous chronic corneal epithelial defect (SCCED)?
Superficial epithelial ulcer which has not healed in 1-2 weeks
Halo of fluorescein under the edges of the ulcer
Minimal corneal oedema
Loose epithelium
What dogs can get Spontaneous chronic corneal epithelial defect (SCCED)?
Any breed of middle aged dogs
What causes Spontaneous chronic corneal epithelial defect (SCCED)?
Poor epithelial adhesion to the stroma
Abnormal basement membrane
Abnormal superficial stroma - has a superficially hyalinised acellular zone where the epithelium cant adhere to the stroma
How do you treat Spontaneous chronic corneal epithelial defect (SCCED)?
Prophylactic topical antibiotic therapy at first
Lubrication
NSAIDs
Surgical treatment usually needed
How do you surgically treat Spontaneous chronic corneal epithelial defect (SCCED)?
Epithelial debridement with dry sterile cotton buds - 50% healing rate
Punctate/grid keratotomy - lots of holes in stromal surface
Diamond burr debridement - 80% success rate
What additional support can you give Spontaneous chronic corneal epithelial defect (SCCED)?
Bandage contact lenses
What cause melting ulcers?
Proteolytic enzymes infiltrating deep stromal ulcers
Matrix metalloproteinases liquify the stroma
How do you treat melting ulcers?
Topical and systemic antibiotics
Antiproteolytic serum drops
Lubrication
Systemic NSAIDs
Often need referral and enucleation
