Eye Care for Animals Micki Armour VMD DACVO THE CORNEA

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Marsha Moody
5 years ago
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1 Eye Care for Animals Micki Armour VMD DACVO THE CORNEA

2 ANATOMY mm thick 4 primary layers Epithelium (5-7 cell layers) Stroma (90% total thickness) Descemet s membrane Endothelium (1 layer)

3 ANATOMY- CORNEAL EPITHELIUM 25-40µm Non-keratinized squamous cells 2-3 layers Polyhedral wing cells 2-3 layers Basal cells Single layer Hydrophobic

4 ANATOMY-CORNEAL STROMA 90% corneal thickness Composed of lamellae + keratocytes Hydrophilic; takes up fluorescein dye

5 Slatter fig 10-24: Descemetocele ANATOMY-DESCEMET S MEMBRANE Produced by corneal endothelium Elastic, thickens with age Does NOT take up fluorescein dye

6 ANATOMY- ENDOTHELIUM Single layer No mitosis Source of Na+/K+ ATPase pumps

7 ANATOMY-CORNEAL INNERVATION Innervation via the long ciliary nerve Ophthalmic branch of CN V Branches enter at mid-stroma Branch anteriorly Hence Superficial cornea is innervated Deep cornea is not Corneal epithelium Corneal endothelium

8 TRANSPARENCY Dependent on 5 basic factors Avascularity Relative dehydration (deturgescence) Hydrophobic epithelium Endothelial Na+/K+ ATPase pumps Orderly arranged stromal collagen Lack of pigment Non-keratinized epithelium

9 NUTRITION Tears (anterior cornea) Aqueous humor (posterior cornea)

10 INDICATORS OF CORNEAL DISEASE Corneal Edema Cellular infiltrate Lipid/mineral deposits Fibrosis Pigmentation Blood vessels Precipitates

corneal/intraocular disease Endothelial dysfunction

11 CORNEAL EDEMA Focal Implies superficial disease Epithelial dysfunction Corneal ulcer Diffuse Implies deep corneal/intraocular disease Endothelial dysfunction Anterior uveitis Glaucoma Deep corneal ulcer Primary endothelial defect

13 CELLULAR INFILTRATE Creamy, opaque infiltrate Superficial cornea Corneal stroma Presume infected!

14 LIPID/MINERAL DEPOSITS Phospholipids, Cholesterol, Calcium ground glass /chalky deposits

15 FIBROSIS Wispy, cloud-like Non-specific sign of previous injury Caused by deposition of poorly organized collagen by stromal keratocytes

16 PIGMENTATION Response to chronic irritation or inflammation Keratoconjunctivitis Sicca (KCS) Chronic superficial keratitis (CSK) Exposure keratitis Species variable Most common in the dog 82% of all pugs! Reversible?

17 ASSESSMENT OF DEPTH

18 NEOVASCULARIZATION Non-specific response to corneal injury Begins w/in 2-3 days of injury Vessels grow ~1mm/day

19 NEOVASCULARIZATION Depth matters! Superficial vessels = superficial disease Branching, fine Entropion, trichiasis, distichiasis, KCS, superficial corneal ulcer Deep vessels = deep disease Dense, hedge-like Uveitis, glaucoma, deep stromal ulcer

20 SUPERFICIAL NEOVASCULARIZATION

21 DEEP NEOVASCULARIZATION

22 INTRASTROMAL CORNEAL HEMORRHAGE

24 KERATIC PRECIPITATES Accumulated inflammatory debris on corneal endothelium Accumulate ventrally Specific sign of intraocular inflammation (uveitis)

26 CORNEAL ULCER - SIMPLE Heals within 5-7 days Corneal healing - Slide and divide Adjacent epithelial cells migrate to cover exposed stroma Begins w/in 1 hour of injury Basal cells reform basement membrane Mitosis of basal epithelial cells

27 CORNEAL ULCER COMPLICATED Persists >7 days= complicated! Underlying cause not addressed (ie ectopic cilium, distichiasis, foreign body, lagophthalmos, KCS, etc) Infected (bacterial, fungal, viral) Indolent boxer ulcer

31 FELINE HERPESVIRUS-ASSOCIATED KERATITIS Infects conjunctival and corneal epithelial cells Persistent and recurrent disease Blepharospasm, epiphora, chemosis, hyperemia Dendritic ulcer=pathognomonic Corneal sequestrum Eosinophilic keratitis Slatter fig 10-42

32 CORNEAL SEQUESTRUM Associated with FHV-1 Necrotic cornea Reaction of dead/dying cornea with tears Painful! Treatment=surgery

33 EOSINOPHILIC KERATITIS Associated with FHV-1 Proliferative, superficial plaque Ddx=SCC, fungal keratitis Diagnosis= cytology

34 CHRONIC SUPERFICIAL KERATITIS PANNUS German shepherd dog/gsd crosses Immune-mediated disease Fibrosis, blood vessels, pigment extend from temporal limbus toward axial cornea Bilateral Associated with UV exposure

35 CORNEAL DYSTROPHY Bilateral Central/paracentral Composed of phospholipid Non-painful No treatment necessary

36 CORNEAL DEGENERATION Calcium/lipid deposits Secondary to corneal injury or inflammation Uni- or bilateral Associated with corneal inflammation May exfoliate, resulting in corneal ulceration

38 MINERAL SLOUGH

43 QUESTIONS?

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