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CVSOH BVSc4 > Ophth - Conditions of cornea and sclera > Flashcards

Ophth - Conditions of cornea and sclera Flashcards

1
Q

What type of cells make up the cornea?

A

Transparent stratified squamous cell epithelium and collagen matrix

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2
Q

What is the limbus? What cells make up the limbus?

A

Transitional zone between cornea and sclera
Stem cells here

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3
Q

What is the sclera?

A

Fibrous tunic which give globe rigidity

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4
Q

How does the cornea maintain transparency?

A

Corneal stroma is a collagen matrix maintained in a relatively dehydrated state
Layered collagen with parallel fibres
No pigments
No vessels
Non-keratinised epithelium

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5
Q

How can you examine structural changes on the cornea? How does it work?

A

Use a slit beam - highlights deviations in depth and flare

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6
Q

What do you use to examine the cornea for exposed corneal stroma?

A

Fluorescein dye

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7
Q

What is fluorescein dye?

A

Orange colour
Mildly irritant
It turns green when water bound
It adheres to exposed corneal stroma
Needs flushing out

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8
Q

What are ocular clinical signs of corneal lesions?

A

Epiphora
Blepharospasm
Conjunctival hyperaemia
Corneal colour change
Anisocoria

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9
Q

What is anisocoria?

A

Two pupils not the same size - myosis on affected side
Sign of reflex uveitis

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10
Q

What is reflex uveitis?

A

Spasm of the ciliary body causing miosis - constriction of the pupil
Is painful

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11
Q

When does reflex uveitis occur?

A

Secondary to anterior ocular pain

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12
Q

How do you treat reflex uveitis?

A

Mydriatics - atropine

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13
Q

What does a blue corneal opacity mean?

A

Oedema - the dehydrated state of the cornea is compromised by and epithelial or endothelial defect

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14
Q

What do epithelial defects causing corneal oedema look like? What causes them?

A

Hazy diffuse, accompanying ulceration

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15
Q

What do endothelial defects causing corneal oedema look like?

A

Mottled, diffuse blue colour

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16
Q

What are some causes of endothelial defects causing corneal oedema?

A

Uveitis, glaucoma, lens luxation, geriatric endothelial degeneration (old age)

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17
Q

What are some causes of red corneas?

A

Vascularisation - superficial or deep neovascularisation
Or haemorrhage

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18
Q

What does superficial neovascularisation look like?

A

Branching trees of red vessels extending from the bulbar conjunctiva
They DO cross the limbus

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19
Q

What is the purpose of superficial neovascularisation?

A

Corneal healing - are a sign of a superficial corneal lesion

20
Q

What does deep neovascularisation look like?

A

Fine straight non-branching vessels radiating from around the limbus
Arise from the limbus
The DO NOT cross the limbus

21
Q

What causes deep neovascularisation?

A

Deep stromal/intraocular cause

22
Q

What cause white colour change to the cornea?

A

Corneal fibrosis - a scar
Metabolic infiltrates
Inflammatory cell infiltrates

23
Q

What is inherited corneal dystrophy?

A

When lipid or minerals are deposited in the eyes causing bilateral white clouds/arcs in the eyes

24
Q

What dogs get inherited corneal dystrophy and what is the treatment?

A

Young dogs
CKCS, husky etc.
Little impact on vision, not treatment necessary

25
Q

What causes black/brown changes to the cornea?

A

Pigmentary keratitis - chronic irritation to the cornea

26
Q

How do you treat/prevent pigmentary keratitis of the cornea?

A

Lubrication daily, especially in brachys

27
Q

What causes pink changes to the cornea?

A

Proliferative cellular infiltrate

28
Q

What are the clinical signs of proliferative cellular infiltrate?

A

Superficial vessels
Pigments
Pink tissue in acute phase
White crystalline spots

29
Q

What is chronic superficial keratitis (‘pannus’)?

A

Progressive bilateral condition of immune mediated origin causing dark clouding of the cornea in German shepherds and greyhounds

30
Q

How can you treat chronic superficial keratitis (‘pannus’)?

A

Can only be controlled
Topical steroids
Immune modulators - cyclosporine (optimmune)

31
Q

What are the steps of epithelial repair in corneal healing?

A

Detachment - of the epithelial cells
Movement - cells slide to fill the defect
Proliferation - epithelial cell mitosis thickening the epithelium
Reattachment - to the basement membrane

32
Q

How long does it take for an uncomplicated superficial epithelial ulcer of the cornea to heal?

A

1-2 weeks

33
Q

How does stromal repair of the cornea occur?

A

Fibroblastic proliferation
Fibres are more disorganised - causes corneal scarring
Remodelling occurs over months to years

34
Q

How does endothelial repair of the cornea occur?

A

Cells at the margin of the wound elongate
cells get spread thinner and migrate
No mitosis possible

35
Q

What is a deep corneal ulcer also called?

A

A stromal ulcer

36
Q

What is the name for complete stromal loss?

A

Descemetocoele

37
Q

What is a descemetocoele? What does it look like?

A

Complete stromal loss - the base of the ulcer looks clear into central eye

38
Q

What is it called when an ulcer occurs without any proceeding signs and is not healing?

A

Spontaneous chronic corneal epithelial defect (SCCED)

39
Q

What are the clinical signs for Spontaneous chronic corneal epithelial defect (SCCED)?

A

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

40
Q

What dogs can get Spontaneous chronic corneal epithelial defect (SCCED)?

A

Any breed of middle aged dogs

41
Q

What causes Spontaneous chronic corneal epithelial defect (SCCED)?

A

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

42
Q

How do you treat Spontaneous chronic corneal epithelial defect (SCCED)?

A

Prophylactic topical antibiotic therapy at first
Lubrication
NSAIDs
Surgical treatment usually needed

43
Q

How do you surgically treat Spontaneous chronic corneal epithelial defect (SCCED)?

A

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

44
Q

What additional support can you give Spontaneous chronic corneal epithelial defect (SCCED)?

A

Bandage contact lenses

45
Q

What cause melting ulcers?

A

Proteolytic enzymes infiltrating deep stromal ulcers
Matrix metalloproteinases liquify the stroma

46
Q

How do you treat melting ulcers?

A

Topical and systemic antibiotics
Antiproteolytic serum drops
Lubrication
Systemic NSAIDs
Often need referral and enucleation

CVSOH BVSc4 (86 decks)

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