Uveitis of undetermined origin is a cause for uveitis that can often not be found by routine hematologic or serologic tests,
especially in older cats in which the uveitis had been present chronically. The typical clinical signs of this idiopathic
uveitis are mild to moderate aqueous flare, keratic precipitates, iris color change and iridal nodules representing mono-nuclear
inflammatory cell infiltrates (lymphocytes and plasma cells). The uveitis is either unilateral or bilateral, and secondary
glaucoma seems to be an inevitable sequelae. Recently, serologic evidence has suggested feline herpesvirus-1 and Bartonella
species may be causes of chronic uveitis in cats.
Corticosteroids remain the primary treatment of uveal inflammation. Topical therapy is the route of choice in most cases,
as effective anterior uveal concentrations are easily achieved. It is imperative that uveitis be treated with cortico-steroids
with the ability to penetrate the epithelial barrier of the cornea. 1 percent prednisolone acetate suspension or 0.1 percent
dexamethasone is an excellent topical steroid choice. The routine initial frequency in moderately severe cases is four-times
daily and then reduced to a maintenance frequency of one to two times daily after the clinical signs have subsided or resolved
(usually within two to three weeks). In acute severe anterior uveal inflammation topical therapy as frequent as every one
to two hours is sometimes necessary. The intensity of aqueous flare is an excellent clinical monitor of the effectiveness
of therapy. Subconjunctival corticosteroids (1-2 mg betamethasone) are also highly effective but are generally reserved for
cases in which the uveitis is unusually severe, or when owner compliance with topical therapy cannot be expected. Needless
to say, subconjunctival therapy must be used with caution in the face of systemic infectious diseases, particularly mycoses.
Systemic corticosteroids are usually not indicated unless the posterior segment is involved, and the cause is non-infectious
Specific antimicrobial therapy is a critical adjunct to palliative anti-inflammatory therapy in cases in which the uveitis
can be attributed to a susceptible organism. For toxoplasmosis, clindamycin hydro-chloride (25 mg/kg daily in divided oral
doses) may be beneficial; however, the use of antimicrobial therapy for Toxoplasma-associated uveitis remains controversial.
The prognosis for uveitis secondary to systemic mycoses is generally poor. Cures from histoplasmosis and cryptococcosis have
been noted with imidazole therapy. Effective specific therapy for FIP and FIV infection has not been reported. On the basis
of the serologic information suggesting a role for Bartonella species as a cause of uveitis in cats, azithromycin therapy
(10 mg/kg PO daily for 21 days) has been advocated for treating cats with this uveitis.
Cycloplegic therapy is not routinely indicated in feline uveitis because the disease is rarely associated with significant
miosis. Atropine solution should be avoided in cats because it invariably travels the short nasolacrimal duct to induce copious
Dr. Hoskins is owner of DocuTech Services. He is a diplomate of the American College of Veterinary Internal Medicine with
specialities in small animal pediatrics. He can be reached at (225) 955-3252, fax: (214) 242-2200, or e-mail: email@example.com