Ophth - Conditions of cornea and sclera

Question 1

What type of cells make up the cornea?

Answer 1

Transparent stratified squamous cell epithelium and collagen matrix

Question 2

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

Answer 2

Transitional zone between cornea and sclera
Stem cells here

Question 3

What is the sclera?

Answer 3

Fibrous tunic which give globe rigidity

Question 4

How does the cornea maintain transparency?

Answer 4

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

Question 5

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

Answer 5

Use a slit beam - highlights deviations in depth and flare

Question 6

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

Answer 6

Fluorescein dye

Question 7

What is fluorescein dye?

Answer 7

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

Question 8

What are ocular clinical signs of corneal lesions?

Answer 8

Epiphora
Blepharospasm
Conjunctival hyperaemia
Corneal colour change
Anisocoria

Question 9

What is anisocoria?

Answer 9

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

Question 10

What is reflex uveitis?

Answer 10

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

Question 11

When does reflex uveitis occur?

Answer 11

Secondary to anterior ocular pain

Question 12

How do you treat reflex uveitis?

Answer 12

Mydriatics - atropine

Question 13

What does a blue corneal opacity mean?

Answer 13

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

Question 14

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

Answer 14

Hazy diffuse, accompanying ulceration

Question 15

What do endothelial defects causing corneal oedema look like?

Answer 15

Mottled, diffuse blue colour

Question 16

What are some causes of endothelial defects causing corneal oedema?

Answer 16

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

Question 17

What are some causes of red corneas?

Answer 17

Vascularisation - superficial or deep neovascularisation
Or haemorrhage

Question 18

What does superficial neovascularisation look like?

Answer 18

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

Question 19

What is the purpose of superficial neovascularisation?

Answer 19

Corneal healing - are a sign of a superficial corneal lesion

Question 20

What does deep neovascularisation look like?

Answer 20

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

Question 21

What causes deep neovascularisation?

Answer 21

Deep stromal/intraocular cause

Question 22

What cause white colour change to the cornea?

Answer 22

Corneal fibrosis - a scar
Metabolic infiltrates
Inflammatory cell infiltrates

Question 23

What is inherited corneal dystrophy?

Answer 23

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

Question 24

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

Answer 24

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

Question 25

What causes black/brown changes to the cornea?

Answer 25

Pigmentary keratitis - chronic irritation to the cornea

Question 26

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

Answer 26

Lubrication daily, especially in brachys

Question 27

What causes pink changes to the cornea?

Answer 27

Proliferative cellular infiltrate

Question 28

What are the clinical signs of proliferative cellular infiltrate?

Answer 28

Superficial vessels Pigments Pink tissue in acute phase White crystalline spots

Question 29

What is chronic superficial keratitis ('pannus')?

Answer 29

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

Question 30

How can you treat chronic superficial keratitis ('pannus')?

Answer 30

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

Question 31

What are the steps of epithelial repair in corneal healing?

Answer 31

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

Question 32

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

Answer 32

1-2 weeks

Question 33

How does stromal repair of the cornea occur?

Answer 33

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

Question 34

How does endothelial repair of the cornea occur?

Answer 34

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

Question 35

What is a deep corneal ulcer also called?

Answer 35

A stromal ulcer

Question 36

What is the name for complete stromal loss?

Answer 36

Descemetocoele

Question 37

What is a descemetocoele? What does it look like?

Answer 37

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

Question 38

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

Answer 38

Spontaneous chronic corneal epithelial defect (SCCED)

Question 39

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

Answer 39

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

Question 40

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

Answer 40

Any breed of middle aged dogs

Question 41

What causes Spontaneous chronic corneal epithelial defect (SCCED)?

Answer 41

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

Question 42

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

Answer 42

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

Question 43

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

Answer 43

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

Question 44

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

Answer 44

Bandage contact lenses

Question 45

What cause melting ulcers?

Answer 45

Proteolytic enzymes infiltrating deep stromal ulcers Matrix metalloproteinases liquify the stroma

Question 46

How do you treat melting ulcers?

Answer 46

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