Uveitis is defined as inflammation of part or all of the uveal tract (iris, ciliary body and choroid). Anterior uveitis or iridocyclitis refers to inflammation of the iris and ciliary body, while posterior uveitis or chorioretinitis describes inflammation of the choroid and retina.

Clinical Signs of Uveitis

Symptoms of anterior uveitis include: blepharospasm, conjunctival hyperemia and chemosis, corneal edema, miosis (small pupil), aqueous flare (breakdown of the blood-aqueous-barrier which allows protein and cells to leak into the anterior chamber). Inflammatory cells may accumulate on the inside of the cornea (keratic precipitates). In cats, a unique form of granulomatous uveitis occurs with nodular accumulations of inflammatory cells within the iris stroma. Hyphema and hypopyon are less-common indicators of more severe inflammation. Inflammation of the ciliary body results in reduced production of aqueous humor and low intraocular pressure. Fundic lesions may include chorioretinal granulomas, hemorrhage, or retinal detachment. The signs can by unilateral or bilateral, and not all of these signs need to be present to diagnose uveitis.

Pathogenesis

Intraocular inflammation is mediated by vascular damage. With such a fundamental underlying pathogenesis, there are many diseases which can secondarily cause uveitis. Many of these are systemic diseases; a thorough systemic evaluation is critical in making a diagnosis. these causes may be conveniently categorized into four large groups: infection, neoplasia, trauma, and immune-mediated (see table). If a patient with uveitis is concurrently ill, the prevailing systemic disease will most likely be the cause for the uveitis. Initial laboratory test should include serum chemistries, complete blood count, heartworm test, serology for FeLV and FIV, and possibly thoracic radiographs. These test may demonstrate evidence of an underlying disease process, and thus help direst further test and possible therapy. If the results of systemic evaluation are negative, an etiologic diagnosis may be difficult to determine and is often presumed to be immune-mediated. A for of immune-mediated panuveitis associated with dermal depigmentation is seen in the Siberian Husky and Akita breeds.

Treatment of Uveitis

If an etiologic diagnosis is established, specific treatment will be directed at the underlying disease process. Ocular treatment is often relatively non-specific with the objective of preventing the often irreversible and visually devastating sequella of intraocular inflammation. anti-inflammatory medications are administered topically and subconjunctivally. In cases established as non-infectious, corticosteroids are often used. Non-steroidal anti-inflammatory agents are used systemically (aspirin, flunixin meg-lumine) and topically (flurbiprofen, suprofen). Atropine is used with caution to dilate the pupil and prevent posterior synechia: monitoring of intraocular pressure is essential as secondary glaucoma is of concern.
 

ANTERIOR UVEITIS IN DOGS AND CATS

Vogt-Koyanagi-Harada syndrome
with severe immune-mediated uveitis

VKH syndrome is also characterized
by vitilligo, poliosis and ulceration
of the mucocutaneous junctions.