Corneal ulcers and keratitis

Question 1

Answer 1

Normal cornea:
* Totally transparent
* No blood vessels
* No spots or pigment
* Smooth

Question 2

What is the Precorneal tear film?

Answer 2

The precorneal tear film is a very thin fluid layer over the corneal surface.

Although it is a part of the tear fluid, it deserves to be considered separately because of its morphologic peculiarities and also because of its physiologic importance for the underlying cornea.

It has 3 layers:
* Superficial layer: oil/lipid produced by the tarsal glands along the eyelid margin.
* Intermediate layer: water/aqueous layer produced by lacrimal and third eyelud gland.
* Mucus layer produced by goblet cells in palpebral conjunctiva.

Question 3

The Cornea has four layers:

Answer 3

(tear film)
corneal epithelium
corneal stroma
descemet’s membrane
endothelium

Question 4

Histology of the epithelial layer of the cornea.

Answer 4

4 layers:
superficial cells
wing cells
basal cells
basal lamina

desmosomes attach the above cells together, and hemidesmosomes attach the basal epithelial lamina to the underlying stroma.

Question 5

Answer 5

Edema caused by endothelium injury.

Question 6

Answer 6

Edema caused by epithelial and stromal injury with ulcer.

Question 7

Answer 7

The Limbus is a ca 1 mm circular boundary between the cornea and sclera/bulbar conjunctiva.

There are a lot of cell types, incl melanocytes, stem cells etc.

Question 8

Keratitis is…?

Categorized broadly as…?

Answer 8

is inflammation of the cornea, can also be a reaction of the cornea to irritation or injury.

• Ulcerative keratitis
• Non-ulcerative keratitis

Question 9

Ulcerative keratitis includes: (3)

Answer 9

• Simple corneal ulceration/corneal ulcers
• Indolent corneal ulcers (indolent basically means non-healing or persistent)
• Complex corneal ulceration/deep corneal ulcers

Question 10

Non-ulcerative keratitis includes: (4)

Answer 10

• Immune-mediated chronic superficial keratitis (pannus, keratitis in horses etc.)
• Keratoconjunctivitis sicca (KCS)
• Pigmentary keratitis
• Eosinophilic keratitis (cats, horses, rabbits)

Question 11

Signs of keratitis. (3)

Answer 11

• Edema
• Vascularization (blood vessels first start
  appearing at the limbus after 4-5 days and grow at a rate of 1 mm per day)
• Infiltration of inflammatory cells that help develop granulation tissue.

Question 12

Answer 12

melting corneal ulcers = enzymatic malacia/ liquefaction of the cornea

usually due to Gram neg. bacteria

Tx includes using patients own serum because it contains anticollagenases, inhibits proteases, and contains growth factors and fibronectin which supports cell adhesion.

Question 13

Answer 13

keratoconjunctivitis

Question 14

Describe SCCED.

Answer 14

Spontaneus chronic corneal epithelial defect is a fancy term for indolent ulcers or non-healing corneal ulcers, are superficial corneal lesions that fail to heal properly due to defects in epithelial adhesion to the underlying stroma.

These defects are most common in middle-aged to older dogs, particularly Boxers and other predisposed breeds.

SCCEDs occur when the basal epithelial cells fail to anchor to the stroma, often due to an abnormal basement membrane or the presence of hyalinized acellular zones.

Clinically, affected dogs present with discomfort, squinting, excessive tearing, and corneal cloudiness.

Treatment typically involves debridement of the loose epithelium, grid keratotomy, diamond burr debridement, or use of contact lenses and therapeutic agents to promote healing.

Despite treatment, SCCEDs can be recurrent and require prolonged management.

cats can get this too

Question 15

Most common cause of corneal ulceration in cats.

Answer 15

herpes virus

Question 16

Immune-mediated keratoconjunctivitis in cats is probably

Answer 16

eosinophilic keratitis

the same in dogs is usually pannus

Question 17

Ddx lists for Keratitis with or without ulcer /keratoconjunctivitis in dogs and in cats and in order of likelihood.

Answer 17

Question 18

Clinical signs of keratitis with corneal ulcer and with or without uveitis. (8)

Answer 18

• Blepharospasm
• Light sensitivity
• Epiphora
• Edema of cornea +/- conjunctiva
• Hyperemia of conjunctiva
• Changes of the cornea /deffects of cornea
• Fluorescein test is positive
• Miosis – but not always (miosis is typical for severe pain, give topical atropine)

Question 19

Answer 19

Epiphora – overflow of tears over the eyelids

Question 20

Clinical signs of chronic keratitis without corneal ulcer (7)

Answer 20

• Edema of cornea +/- conjunctiva (chemosis)
• Hyperemia of conjunctiva
• Changes of the cornea /deffects of cornea
• Infiltration/pigmentation of cornea
• Vascularisation of cornea
• Fluorescein test is usually negatiive
• Blepharospasm can be but usually not

Question 21

Schirmer tear test result that is diagnostic of KCS.

Answer 21

≤ 10 мм/60 sеc

Question 22

Answer 22

Pigmentary keratitis

Inflammation of the conjunctiva and cornea resulting in total pigmentation, no longer transparent cornea,
the fluorescein test may be negative.

Is a typical sign of low tear production aka KCS.

Question 23

What should you remember about ulcers found in the late stage of healing?

Answer 23

the fluorescein test may be negative, because the ulcer is covered by new epithelium.

Question 24

Healing of asimple superficial corneal ulcer takes

Answer 24

1-7 days.

Question 25

Canine Indolent Ulcers are

Answer 25

* Superficial corneal ulcers that are non-responsive to topical medication. * Have loose, non-adherent epithelial margins surrounding the ulcer. ## Footnote Also called SCCEDs – Superficial chronic corneal epithelial defects, and also known as Boxer ulcers, and recurrent epithelial erosions.

Question 26

Pathogenesis of Canine Indolent Ulcers

Answer 26

Pathogenesis is thought to involve a defect in stromal-epithelial adhesion. Sliding with blinking and eye movement causes the epithelium to break down with resultant superficial ulceration and the inability of the epithelium to adhere to the underlying stroma results in abortive and prolonged healing. More often than not a history of precipitating trauma cannot be elicited and the majority occur spontaneously. ## Footnote SCCEDs – Superficial chronic corneal epithelial defects

Question 27

Healing time for deep ulcers.

Answer 27

Deep ulcers/stromal ulcers take 4-8 weeks to heal. Healing occurs with vascularisatsion and infiltration of inflammatory cells and scarring.

Question 28

What risks do corneal ulcers all have? (2)

Answer 28

* Always a risk of secondary bacterial infections * Always a risk of secondary uveitis

Question 29

What is this?

Answer 29

Temporary correction of entropion in dogs, "tacking" procedure until surgical correction can be carried out. You can use this procedure in young growing animal or if spastic entropion present (temporary entropion coused by pain, blepharospasm).

Question 30

Whats this?

Answer 30

Temporary covering of the cornea with the third eyelid for protection.

Question 31

Prevention or treatment of secondary bacterial infection in the corneal ulcer:

Answer 31

* Use local antibiotic treatment with Gr+ spectrum. * When there's danger of, or suspected melting ulcer, a drop of ciprofloxacin, tobramycin over the first two days every 1-2 hours, then depending on the situation, lowering to 4 times a day. * When melting ulcers and perforations are present - systemic treatment with broad-spectrum antibiotics, with emphasis on Gr- microflora. * For Cats - chloramphenicol locally, tetracycline antibiotics systemically and locally.

Question 32

Analgesia options and combos for corneal ulcers. (4)

Answer 32

* Topical mydriatics and cycloplegics (drops of atropine 1%) * Additional hydration of the cornea and conjunctiva of preparations of artificial tears or gels. * The use of protective lenses, if no melting ulcers. * Systemic use of nonsteroidal anti-inflammatory drugs. Can use all of the above in the same case.

Question 33

Prevention or treatment of secondary uveitis when ulcer present. (3)

Answer 33

* Topical mydriatics and cycloplegics (drops of atropine 1%) * Systemic use of nonsteroidal anti-inflammatory drugs or * Systemic use of steroidal anti-inflammatory drugs, corticosteroids.

Question 34

Describe The use of enzyme inhibitors/proteinases for melting ulcers.

Answer 34

* Blood serum (usually autologous) every 1-4 hours locallly. * EDTA 0,05-0,2% solution locally, by chelating divalent cations like calcium and zinc, which are essential for the activity of matrix metalloproteinases. * Acetylcysteine solution 5% every 1-4 hours locally. Acetylcysteine thins out mucus, making dry eyes feel more comfortable. * Tetracycline (ointment, drops 0,025-0,1 %) or systemic tabl 5 mg/kg 1-2 x days. Tetracyclines have been shown to inhibit proteinases produced by the corneal epithelium and bacteria. ## Footnote Proteinases promote collagenolysis which can lead to melting ulcers and globe rupture.

Question 35

Whats this?

Answer 35

Removal of non-adherent epithelium if its an indolent ulcer. Removal with cotton tipped applicators and diamond burrs to scarify the corneal tissue (stroma) so that the new cells have something to stick to.

Question 36

Describe tx of Deep corneal ulcers with exposed descemet membrane.

Answer 36

Risk of corneal perforation so Surgery for closing the ulcer. Conjunctival (1) keratoconjunctival flap (2) (A combined corneal and conjunctival flap ) or artificial cornea (3)

Question 37

Possible causes of corneal sequestrum in cats.

Answer 37

* Entropion * FHV inf * Drying of the cornea during general anesthesia * Mostly seen in purebred cats such as Persians and British Short Hair cats * Often bilateral, but not at the same time.

Question 38

3 major tx options for feline corneal sequestrum:

Answer 38

* Conservative treatment with antibiotic and lubricating ointments to reduce irritation and prevent infection until the eye has shed the sequestra by itself. * Surgical excision of the sequestra and placement of a soft contact lens. * Surgical excision of the sequestra followed by a grafting procedure to provide support for the affected area of cornea and to reduce the risk of the sequestra coming back. ## Footnote Specific treatment in specific diseases (immune-mediated keratitis, dry eye syndrome).

Question 39

identify

Answer 39

Eosinophilic keratitis in cats

Question 40

identify

Answer 40

Chronic superficial keratitis in dog/pannus ## Footnote Corneal vascularisation, edema, infiltration, some times pigmention.

Question 41

identify

Answer 41

Chronic superficial keratitis in dog/Pannus * Corneal vascularisation, edema, infiltration, some times pigmention. * Without corneal ulcer and pain

Question 42

Describe Chronic superficial keratitis in dogs.

Answer 42

Pannus Genetic predisposition in * German Shepherd and their crosses * Collies * Greyhound * Siberian husky * Ultraviolet light exposure has been suspected factor that alters corneal antigen recognition and results in an immune- mediated response. (use doggy sunglasses)

Question 43

Treatment of Chronic superficial keratitis in dogs. (Pannus)

Answer 43

Locally corticosteroids (dexamethasone) 4 x daily for 4 weeks, then continue 2 x daily or with local cyclosporine drops 1-2% or ointment 0,2% (optimmune).

Question 44

Treatment of secondary pigmentary keratitis/corneal melanosis.

Answer 44

* Treatment of primary causes: macroblepharon, entropion, dry eye etc. * The Pigmentation is usually permanent. * We can prevent pigmentation or decrease superficial pigmentation by using cyclosporine drops 1-2% or ointment 0,2% locally. * Topical steroid therapy only, if it is an accurate diagnosis (usually immune-mediated inflammation). * Fluorescein test should be performed before beginning medication with local corticosteroids as otherwise theyre contraindicated!