Corneal ulcers and keratitis Flashcards
Normal cornea:
* Totally transparent
* No blood vessels
* No spots or pigment
* Smooth
What is the Precorneal tear film?
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.
The Cornea has four layers:
(tear film)
corneal epithelium
corneal stroma
descemet’s membrane
endothelium
Histology of the epithelial layer of the cornea.
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.
Edema caused by endothelium injury.
Edema caused by epithelial and stromal injury with ulcer.
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.
Keratitis is…?
Categorized broadly as…?
is inflammation of the cornea, can also be a reaction of the cornea to irritation or injury.
- Ulcerative keratitis
- Non-ulcerative keratitis
Ulcerative keratitis includes: (3)
- Simple corneal ulceration/corneal ulcers
- Indolent corneal ulcers (indolent basically means non-healing or persistent)
- Complex corneal ulceration/deep corneal ulcers
Non-ulcerative keratitis includes: (4)
- Immune-mediated chronic superficial keratitis (pannus, keratitis in horses etc.)
- Keratoconjunctivitis sicca (KCS)
- Pigmentary keratitis
- Eosinophilic keratitis (cats, horses, rabbits)
Signs of keratitis. (3)
- 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.
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.
keratoconjunctivitis
Describe SCCED.
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
Most common cause of corneal ulceration in cats.
herpes virus
Immune-mediated keratoconjunctivitis in cats is probably
eosinophilic keratitis
the same in dogs is usually pannus
Ddx lists for Keratitis with or without ulcer /keratoconjunctivitis in dogs and in cats and in order of likelihood.
Clinical signs of keratitis with corneal ulcer and with or without uveitis. (8)
- 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)
Epiphora – overflow of tears over the eyelids
Clinical signs of chronic keratitis without corneal ulcer (7)
- 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
Schirmer tear test result that is diagnostic of KCS.
≤ 10 мм/60 sеc
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.
What should you remember about ulcers found in the late stage of healing?
the fluorescein test may be negative, because the ulcer is covered by new epithelium.
Healing of asimple superficial corneal ulcer takes
1-7 days.
Canine Indolent Ulcers are
- Superficial corneal ulcers that are non-responsive to topical medication.
- Have loose, non-adherent epithelial margins surrounding the ulcer.
Also called SCCEDs – Superficial chronic corneal
epithelial defects, and also known as Boxer
ulcers, and recurrent epithelial erosions.
Pathogenesis of Canine Indolent Ulcers
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.
SCCEDs – Superficial chronic corneal epithelial defects
Healing time for deep ulcers.
Deep ulcers/stromal ulcers take 4-8 weeks to heal.
Healing occurs with vascularisatsion and infiltration of inflammatory cells and scarring.
What risks do corneal ulcers all have? (2)
- Always a risk of secondary bacterial infections
- Always a risk of secondary uveitis
What is this?
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).
Whats this?
Temporary covering of the cornea with the third eyelid for protection.
Prevention or treatment of secondary bacterial infection in the corneal ulcer:
- 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.
Analgesia options and combos for corneal ulcers. (4)
- 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.
Prevention or treatment of secondary uveitis when ulcer present. (3)
- Topical mydriatics and cycloplegics (drops of atropine 1%)
- Systemic use of nonsteroidal anti-inflammatory drugs
or - Systemic use of steroidal anti-inflammatory drugs,
corticosteroids.
Describe The use of enzyme inhibitors/proteinases for melting ulcers.
- 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.
Proteinases promote collagenolysis which can lead to melting ulcers and globe rupture.
Whats this?
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.
Describe tx of Deep corneal ulcers with exposed descemet membrane.
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)
Possible causes of corneal sequestrum in cats.
- 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.
3 major tx options for feline corneal sequestrum:
- 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.
Specific treatment in specific diseases (immune-mediated keratitis, dry eye syndrome).
identify
Eosinophilic keratitis in cats
identify
Chronic superficial keratitis in dog/pannus
Corneal vascularisation, edema, infiltration, some times pigmention.
identify
Chronic superficial keratitis in dog/Pannus
- Corneal vascularisation, edema, infiltration, some times pigmention.
- Without corneal ulcer and pain
Describe Chronic superficial keratitis in dogs.
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)
Treatment of Chronic superficial keratitis in dogs.
(Pannus)
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).
Treatment of secondary pigmentary keratitis/corneal melanosis.
- 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!
