Week 1- Approach to Diseases of the Cornea and Conjunctiva Flashcards
What is corneal transparency?
The ability of the cornea to transmit light without significant scattering
How is corneal transparency acheived?
- Small diameter and lamellar arrangement of collageb fibres
- absence of blood vessels
- Absence of pigment
dehydration
What does corneal oedema look like?
Excess fluid accumulation within the stroma, blue ‘fluffy’, indistinct borders
What does corneomalacia look like?
‘stromal melting’
* result of oozing and sagging of the stroma, due to collagen destruction by proteinases
What is pigmentary keratitis?
nonspecific response to chronic corneal irritation
melanin is deposited from the corneal epithelium and anterior stroma
melanocytes then mingrate from the limbus
What are the two types of keratitis?
- Ulcerative
- Non-Ulcerative
What breeds is SCEED typically seen in?
- Boxers
- Corgis
- Middle aged/ older animals
What are the characteristics of SCEED?
- Develop in the absence of trauma
- Shallow and slow to heal
- Blurred edges-fluoresceine uptake
underneath the epithelium - Nonadherent epithelium
- Spontaneous occurrence
- Usually unilateral but occasionally
bilateral - Abnormal adhesion between epithelial
cells and stroma
What is the treatment for chronic superficial keratitis?
- No cure, requires life-long therapy
- Initially topical corticosteroid (1% prednisolone,
0.1% dexamethasone) 3-4x daily - Topical cyclosporine (0.2-2%) with or without
corticosteroids 2x daily
What are some examples of non-penetrating corneal lacerations?
- Common ocular emergency
- Cat claw, thorn, nail etc.
- Partial thickness puncture or laceration
- Can lead to a corneal flap
- Medical treatment –if stromal exposure is small – frequent
re-examinations necessary - Debridement, antibiotics, analgesic
- Direct suturing or conjunctival graft
Why should a keratotomy never be performed in cats?
Leads to corneal sequestration (areas of necrotic tissue)
What is the gold-standard test for FHV-1 in cats?
PCR testing-gold standard, use cytobrush to collect
enough material
What are the clinical signs of FHV-1 keratitis in cats?
Often unilateral
* Epiphora- crying in one eye
* Blepharospasm
* Dendritic lesions-short lasting
* Geographic ulceration
* May look like SCCED but the pathophysiology is
different
* Qualitative tear film disease (the eye looks very
watery but the cornea is dry!)
* Stromal keratitis is caused by immune mediated
inflammation
How might you treat FHV-1 keratitis in cats?
Topical antibiotic (Chloramphenicol, Fusidic acid)
* Famciclovir 90mg/kg q12h
* Topical ganciclovir (Virgan) q 6-8h for 21days
* Autologous serum
* Tear replacement therapy
* Environmental modifications- stress reduction,
overcrowding control
How does feline eosinophillic keratitis present?
White and pink deposits (resembling cottage
cheese)slowly progressive
* Affects conjunctiva, epithelium and superficial stroma
* Usually starts at the limbus (immunologically most active
part of the eye)
* Young to middle aged cats
How might you treat feline eosinophillic keratitis?
- Not curable
- resolution can take weeks -> Months
- Can use tear replacement therapy
What are the early clinical signs of corneal sequestrum in cats?
epiphora, brown stromal discoloration
What are the late clinical signs of corneal sequestrum in cats?
firm dark brown lesion (stromal necrosis)
superficial vascularization
What cat breed may be predisposed to corneal sequestrum?
Sphynx breed
What is conjunctivitis characterised by?
hyperaemia, ocular discharge and chemosis in an eye with
normal IOP and NO aqueous flare
what is the general treatment reccomendation for bacterial conjunctivitis
- completely remove the crusts and exudates
- topical broad-spectrum antibiotic
- systematic antibiotic therapy if blepharitis, dermatitis or otitis is present
What is quantitative KCS?
a decrease in the aqueous component of the tear film as
measured with the Schirmer tear test (STT); it is recognized more commonly
in veterinary medicine.
What is Qualitative KCS?
decrease in the lipid or mucin components of the tear
film and diagnosed by documenting decreased tear film breakup time (TBUT).
What are the clinical signs of quantitative KCS?
- Thick, adherent mucopurulent discharge
- Conjunctivitis
- Blepharospasm
- Dry, lustreless corneal appearance
- Ulcerative keratitis, ranging from
superficial ulcers to perforations - Corneal pigmentation, neovascularization
What is cyclosporine A?
Immunomodulator, antiinflammatory
* Inhibits production of interleukin-2
(proliferation of T-helper and
cytotoxic T cells) in the lacrimal
gland
* Directly stimulates lacrimation
* Decreases pigmentation
* Normalizes goblet cell mucin
secretion
81.8% of dogs showing
improvement
* STT < 2 mm/min - response in 50%
* STT ≥ 2 mm/min – response in 80%
What is tacrolimus?
Mechanism of action
compared with CsA but
more potent,
* Patients that are
unresponsive to CsA may
respond to tacrolimus
* Second line treatment if
not responding to CsA
* Off-label use
What is the function of tear replacement therapy in KCS?
Provides lubrication
* Lifelong therapy
* Available as solutions, gels,
and ointments
What is the function of pilokarpine as a KCS treatment?
Neurogenic KCS (ipsilateral
dry nose+ low STT)
* Parasympathomimetic
* Stimulates tear production
