Cornea

Question 1

4 layers of cornea and function

Answer 1

1. epithelium - hydrophobic, repel and protect
2. Stroma - hydrophilic and lamellar arrangment is responsible for clarity
3. Descemet’s membrane
4. endothelium - pumps fluid out

Question 2

Limbus

Answer 2

corneoscleral junction

Question 3

Corneal function

Answer 3

Major refractive structure of the eye

Ocular protection

Question 4

4 tenants of corneal pathology

Answer 4

1. Edema
2. vascularization
3. pigmentation
4. scarring

Question 5

How does the corneal epithelium heal?

Answer 5

Sliding then mitosis

Question 6

How does corneal stroma heal?

Answer 6

Sliding then mitosis. Fibroblasts proliferate and lay down collagen and results in scarring

Question 7

How does corneal edema occur?

Answer 7

Epithelial damage (allowing in) or Endothelial damage (not pumping out)

Question 8

Can corneal endothelium regenerate in adult animal?

Answer 8

NOPE

Question 9

How does pigmentation occur?

Answer 9

response to chronic irritation or inflammation

Question 10

How does vascularization occur?

Answer 10

response to corneal or intraocular disease. grow from limbus to defect
Surface disease results in arborizing vascularization
Ocular disease results in more linear vascularization

Question 11

What is a Dermoid?

Answer 11

Normal skin in an abnormal place (usually haired).

Complete excision is curative.

Question 12

Persistent pupillary membranes

Answer 12

come from Iris, treatment unnecessary unless cause debilitating disease

Question 13

What causes corneal ulcers?

Answer 13

Trauma #1

KCS, exposure keratitis, chemical contact

Question 14

Ulcer therapy

Answer 14

1. Topical abx
2. Topical atropine sulfate
3. Protease inhibitors
4. Conjunctival flap surgery

DO NOT USE STEROIDS

Question 15

What therapy DON’T you use for corneal ulcers?

Answer 15

STEROIDS!!! NO!

Question 16

Key clinical features of Boxer Ulcer/Spontaneous Chronic Corneal Epithelial Defect (SCCED)

Answer 16

refractory ulcers; middle aged dogs
superficial stroma with a RIM of loose corneal epithlelium
+/- vascularization and pain
TX: Debridement of loose epithelial tissue

Question 17

Corneal Abscesses

Answer 17

off-white/yellow opacity of inflammatory cells in stroma
Epiphora and blepharospasm, uncomfortable
Vascularization and edema usually
More common in Large Animals
TX: Topical antibiotic that can penetrate epithelium (chloramphenicol and fluoroquinolones)
or you can do surgery and remove abscess

Question 18

Chronic superficial Keratitis

Answer 18

Pannus or German shepherd pannus
Superficial vascularization and pigmentation of cornea starting LATERALLY
Faint, white infiltrates at leading edge of lesion
NON-ulcerative and NON-painful
Immune-mediated condition; more severe at high altitude due to UV radiation
CANNOT BE CURED

Question 19

TX of Chronic Superficial Keratitis

Answer 19

NON-ulcerative and NON-painful starting laterally

TX: Anti-inflammatory/immune suppressive — Cyclosporine or tacrolimus or corticosteroids

Question 20

Lipid keratopathy and etiologies

Answer 20

Lipid deposition in cornea – appears Crystalline

1. Inherited, dystrophic condition
2. systemic lipid metabolism disturbance (hypothyroidism)
3. previous or ongoing corneal disease (previous ulceration, pannus or NGE)

TX: not sight threatening so usually none
Note: topical steroids may cause or exacerbate

Question 21

Endothelial dystrophy/degeneration

Answer 21

Severe bilateral edema in Older Animals
Breeds: Boston Terrier, Chihuahua, Dachsund, Basset Hound
Edema causes BULLA formation and recurrent Ulceration
TX: Topical Abx for ulcers if they occur; topical hyperosmotic for edema/prevent bulla formation/rupture; Thermal keratoplasty for non-stop recurrent ulcers

Question 22

What is Dendritic Ulceration pathognomonic for in cats?

Answer 22

Feline Herpes – don’t get to stroma so ID with Rose Bengal

Tx: Abx if ulceration through epithelium; anti-virals can work but not definitively

Question 23

Eosinophilic keratitis

Answer 23

Cats and Horses
Variably sized proliferative lesions/plaques on corneal surface
Dx: corneal scraping reveals Eosinophils, Mast cells some lymphocytes and plasma cells
Tx: Topical corticosteroids, Topical cyclosporine, oral Ovacan in Cats (megestrol acetate)

Horses get ulcers and may need surgical removal to heal

Question 24

Feline corneal sequestrum

Answer 24

tan to black plaque in central or paracentral cornea
vascularization common, VERY PAINFUL
Slow healing corneal ulcers precede sequestrum formation
Tx: Surgical Removal by keratectomy followed by conjuctival flap. Can allow body to try and slough off but only recommend of NON-Painful patients