A Colour Guide to the Cornea

Question 0

What can cause vascularisation of the cornea?

Answer 0

Irritants

Chronic diseases such as canine LPI or pannue and feline eosinophilic keratitis

Question 1

What colour does vascularisation make the cornea go?

Answer 1

Red/pink

Question 2

What colour does oedema cause the cornea to turn?

Answer 2

Blue

Question 3

What can cause corneal oedema?

Answer 3

Superficial corneal level (ulcers and vascularisation)

Intra-ocular disease such as uveitis, glaucoma, lens luxation

Question 4

What colour do deposits and infiltrates turn the eye?

Answer 4

White/yellow

Question 5

What deposits or infiltrates can colour the cornea?

Answer 5

Cholesterol/calcium
Scar
Abscess
Fluorescein

Question 6

What colour does pigment make the cornea?

Answer 6

Brown to black

Question 7

What can cause pigment in the cornea?

Answer 7

Irritants and chronic disease
Scar
Sequestra mainly in cats

Question 8

Which eyelid and hair abnormalities can cause irritation to the cornea?

Answer 8

Entropion
Ectropion
Trichiasis
Distichiasis
Ectopic cilium

Question 9

What is ectropion?

Answer 9

Where the eyelid comes away from the surface of the eye

Question 10

What is entropion?

Answer 10

Where the eyelid curls into the surface of the eye

Question 11

What is distichiasis?

Answer 11

Where a hair grows out of the meibomian gland

Question 12

What is trichiasis?

Answer 12

Where facial hairs touch the surface of the eye

Question 13

What is an ectopic cilium?

Answer 13

An eyelash that exits through the conjunctiva of the eyelid

Question 14

Which dogs are more susceptible to medial lower eyelid entropion +/- canthus?

Answer 14

Brachycephalics

High prevalence in the pug

Question 15

Which dogs are more susceptible to upper eyelid entropion?

Answer 15

Cockers, hounds etc.

Heavy ears and forehead

Question 16

Which dogs are more susceptible to lateral upper and lower eyelid and lateral canthus entropion?

Answer 16

Shar-Peis

Question 17

Which factors predispose to lateral lower eyelid entropion?

Answer 17

Young dogs, medium-large breed
Older cats
Blepharospasm

Question 18

Which chronic infiltrative immune-mediated diseases cause corneal vascularisation?

Answer 18

Canine Lymphocytic Plasmacytic Infiltrate

Feline Eosinophilic Keratitis (can also affect horses and rabbits)

Question 19

Which chronic non-infiltrative immune-mediated disease can cause vascularisation of the cornea?

Answer 19

Canine dry eye (Keratoconjunctivitis sicca)

Question 20

What are the other names for canine lymphocytic plasmacytic infiltrate?

Answer 20

Corneal pannus (layer upon layer)
Chronic superficial keratitis (CSK)

Question 21

Which breeds are predisposed to canine lymphocytic plasmacytic infiltrate?

Answer 21

German Shepard Dogs
Greyhounds
Rottweilers

Question 22

What can make canine lymphocytic plasmacytic infiltrate worse?

Answer 22

Sunlight, snow or high altitude

Question 23

What are the signs of canine lymphocytic plasmacytic infiltrate?

Answer 23

Cellular infiltrate and vascularisation +/- pigment

Dorsolateral corneoconjunctiva usually affected first

Question 24

How is cytology of canine lymphocytic plasmacytic infiltrate performed?

Answer 24

Proxymetacaine (0.5%) topical anaesthetic and then cytobrush and diff quik stain

Question 25

What are the properties of proxymetacaine 0.5%?

Answer 25

OOA 30-60 seconds DOA 15-30 minutes Decreases blink, increased dryness, ulcer formation

Question 26

What is seen if there is third eyelid involvement with canine lymphocytic plasmacytic infiltrate?

Answer 26

Depigmentation and hyperaemia

Question 27

What species can eosinophilic keratitis affect?

Answer 27

Cats (mainly) Rabbits Horses

Question 28

What are the signs of eosinophilic keratitis?

Answer 28

Cellular infiltrate and vascularisation with dorsolateral corneoconjunctival area usually affected first Infiltrate is pink to white and in the form of plaques or clumps

Question 29

Which cells are involved in eosinophilic keratitis?

Answer 29

Neutrophils Plasma cells Clusters of eosinophils - diagnostic

Question 30

What can make eosinophilic keratitis difficult to diagnose?

Answer 30

Cellular infiltrate may uptake stain

Question 31

What is the general treatment regimen for LPI and EK?

Answer 31

Topical immunomodulators starting with 4-6x daily then tapering off slowly over many weeks (reduce by 1x a day every 2 weeks) Maintain at a minimum of 2x a day for 2-4 weeks and re-examine May reduce to 1x a day or EOD for maintenance

Question 32

Which topical immunomodulator is used to control LPI in dogs?

Answer 32

Topical ciclosporin but need to combine with a steroid to start with

Question 33

Which topical immunomodulatory drug is used to control EK in cats?

Answer 33

``` Topical steroid (dexamethasone phosphate) Not ciclosporin as it is irritant in cats ```

Question 34

What supports a diagnosis of canine keratoconjunctivitis sicca?

Answer 34

History of recurring persisting ocular surface problems Clinical signs of conjunctivitis, surface dullness, mucus discharge, ulcers Low Schrimer Tear Test - 1 result

Question 35

What is the treatment for canine keratoconjunctivitis sicca?

Answer 35

Topical ciclosporin BID or SID, long term (for life) | Preservative free viscous tears

Question 36

What are the characteristics of acute canine KCS?

Answer 36

Affects mostly young or old dogs Less mucus and less hyperaemia than chronic cases Often ulcerative

Question 37

What are the characteristics of chronic KCS?

Answer 37

Scarring Pigment changes Vascularisation

Question 38

How is KCS treatment success evaluated?

Answer 38

Improvement in at least 3 out of 5: | Mucus production, redness, comfort, keratitis, tear readings

Question 39

How do ulcers turn the cornea red?

Answer 39

Develop a red bed of granulation tissue formed by coalescing blood vessels

Question 40

Where do corneal blood vessels arise from?

Answer 40

Limbus

Question 41

What does lipid infiltrate of the cornea look like?

Answer 41

Reflective white crystals in superficial stroma

Question 42

What are the characteristics of primary lipid infiltrate (dystrophy)?

Answer 42

Most common No vascularisation In several breeds such as CKCS, Huskies

Question 43

What are the characteristics of secondary lipid infiltrate?

Answer 43

Degeneration accompanied by vascularisation Associated with chronic corneal problems Associated with hyopthryroidism

Question 44

What is the general progression of lipid infiltrate?

Answer 44

Slowly progressive

Question 45

What is the treatment for lipid infiltrate?

Answer 45

Dietary control theorised by some to help slow down progression Topical steroids and oestrus can speed up progression Might be removed if large and blocking vision but non-painful

Question 46

How does calcium infiltrate appear clinically?

Answer 46

Chalky, non-reflective white crystals in superficial stroma | May adopt a reticulated pattern

Question 47

What is the pathogenesis of calcium infiltrate?

Answer 47

Secondary to degeneration Associated with chronic corneal problems Accompanied by vascularisation

Question 48

What treatment is necessary for calcium infiltrate?

Answer 48

May need removal via keratectomy if painful as can spiculate and spicules break through the epithelium causing pain

Question 49

What can cause corneal scarring?

Answer 49

Chronic keratitis, ulcerative keratitis and surgery

Question 50

What is the clinical appearance of corneal scarring?

Answer 50

Non reflective, non crystalline, dull

Question 51

What are the characteristics of corneal abscesses?

Answer 51

An accumulation of WBCs Enzymes can lead to rapid collagen melting Not a pocket of fluid as it can't be drained

Question 52

What causes corneal oedema?

Answer 52

Loss of epithelium Loss of endothelium Vascularisation resulting in leakage

Question 53

What is the appearance of corneal oedema?

Answer 53

Blue mottled appearance

Question 54

What is the pathogenesis of corneal oedema?

Answer 54

Loss of epithelium due to an ulcer Endothelial damage due to increased intra-ocular pressure/inflammation/primary endothelial degeneration/contact Vascularisation as developing vessels leak

Question 55

What is the pathogenesis of pigmentary keratitis in pugs?

Answer 55

Associated with medial canthal and lower eyelid entropion Overexposure of the cornea and conjunctiva Occasionally associated with dry eye (KCS) Very proliferative pigment response that starts medialy Can be sight impairing to blinding by 2 years of age

Question 56

What is the pathogenesis of sequestra in cats?

Answer 56

Idiopathic and spontaneous but associated with chronic irritation commonly in the central cornea or medially with medial lower eyelid entropion

Question 57

What is the progression of sequestra of cats?

Answer 57

Light tan discolouration of superficial stroma, intact epithelium Darkening of lesion, loss of epithelium, vascularisation, pain Hardening and deepening of lesion