Uveitis - Cat and Dog
Introduction
Uveitis refers to inflammation of the uvea.
Various parts of the uvea, aqueous humour and vitreous are continuous, and uveitis often involves many ocular structures.
The retina and choroid are adjacent and are frequently inflamed together.
Anterior uveitis referes to inflammation of the iris and ciliary body whereas posterior uveitis refers to inflammation of the choroid.
The pathogenesis of uveitis is still poorly understood, but immunologic reactions are involved. There are alterations in the vascular structure and permeability of uveal blood vessels following inflammation, and immune complexes can be deposited in vessels and lead to a chronic and recurrent disease.
Causes
Causes of uveitis in cats include:
Infectious causes:
- Feline Infectious Peritonitis
- FeLV causing lymphosarcoma
- FIV
- Feline Herpesvirus 1
- Toxoplasmosis
- Bartonella spp
- Systemic mycoses (cryptococcosis, histoplasmosis, blastomycosis, coccidiomycosis)
Neoplasia: Lymphoma, melanoma
Metabolic causes: hypertension, coagulopathies
Immune-mediated: cataract, phagoclastic uveitis, vasculitis
Trauma: blunt or penetrating injuries, corneal foreign bodies
Idiopathic
Clinical Signs
Cats will usually present because the owner has noticed a change in one or both eyes. There is usually a colour change, cloudy or red most commonly.
The condition may be unilateral or bilateral. Bilateral disease is more common with systemic and auto-immune diseases, whereas trauma usually lead to unilateral signs.
Acute uveitis causes: pain, ciliary flush, miosis, aqueous flare, spongy swollen iris, decreased intra-ocular pressure
Hyphaema may be present and make the eye appear red.
A combination of aqueous flare, hypopyon, keratic precipitates and cataract will make the eye appear cloudy.
A fundus examination may reveal chorioretinitis and retinal detachment.
With chronic uveitis, additional signs may include: neovascularisation of the iris, changes in iris pigmentation, secondary iris atrophy, synechiae, glaucoma and blindness.
Diagnosis
A thorough clinical examination and ophthalmic examination should enable a diagnosis of uveitis to be made.
Further investigation into the cause of the uveitis should include:
Complete haematology and biochemistry
Urinalysis
Thoracic radiography
Serological testing for Toxoplasma, FeLV, FIV
Idiopathic uveitis is a diagnosis of exclusion.
Treatment
Treatment should be targeted at the specific cause if one has been found.
Additional treatment can be given to:
Control inflammation: topical or systemic corticosteroids, topical or systemic NSAIDs, topical immunosuppressive drugs such as cyclosporin.
Prevent undesirable sequelae: mydriatics to reduce synechiae formation and secondary glaucoma (atropine or tropicamide), anti-glaucoma agents if necessary
Relieve pain: atropine helps reduce ciliary spasm. The patient can also be placed in a dark room to alleviate photophobia. A systemic opioid analgesia may be necessary in severe cases.
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References
Maggs, D. (2008) Slatter's fundamentals of veterinary ophthalmology Elsevier Health Sciences
Turner, S. (2008) Small animal ophthalmology Elsevier Health Sciences
Peiffer, R. (2008) Small animal ophthalmology: a problem-oriented approach Saunders