Uveitis, evidenced by low IOP, was present in the left eye. The left eye also had posterior synechiae and a blood clot in
the pupil. The fundus could not be visualized in either eye.
2. The cat's right eye had anterior synechić and fibrin in the pupil.
The rest of the physical examination findings were normal, and the cat weighed 11.9 lb (5.4 kg).
Differential diagnoses for uveitis include trauma, systemic infection, neoplasia, and immune-mediated causes. Coagulopathies
and systemic hypertension can also cause hyphema.
The most common intraocular primary neoplasms are iris melanoma or ciliary body adenocarcinoma.1 Ocular neoplasia can also result from metastatic cancer, most commonly lymphosarcoma.
Viral causes of uveitis in cats include feline infectious peritonitis (FIP), FeLV, and FIV infections. Cryptosporidiosis,
blastomycosis, histoplasmosis, coccidioidomycosis, and, rarely, candidiasis should be considered depending on the region.4 The algae Prototheca species can also cause uveitis.1 Bacterial causes include Bartonella, Mycoplasma, and Ehrlichia species.4 Toxoplasmosis is a common protozoal cause, which often leads to posterior segment disease, including chorioretinitis and
Bartonella henselae and herpesvirus infection have also more recently been implicated as causing uveitis.6
While characteristic signs of specific infectious diseases exist (e.g. pars planitis and chorioretinitis caused by toxoplasmosis), studies have shown that intraocular changes are often indistinguishable
among various infectious diseases.7
Specific immune-mediated diseases in the eye include lens-induced uveitis (phacoclastic uveitis), Vogt-Koyanagi-Harada-like
syndrome, and immune-mediated vasculitis. Immune-mediated causes tend to be a diagnosis of exclusion. However, many systemic
inflammatory responses (including systemic infection) can also lead to a secondary immune-mediated uveitis. For example, no
infectious agents may be identified in the aqueous humor after anterior chamber paracentesis, but uveitis is still present
because of systemic infection and activated T cells that have migrated back to the eye.8
A systemic infection was suspected in this cat because there was no known history of trauma, the ocular disease had progressed,
and the cat was lethargic and inappetent. The differential diagnoses were bartonellosis, toxoplasmosis, and FIP, FIV, or FeLV
infection (although the test results for FIV and FeLV were negative). Other infectious agents were less likely since the cat
lived in Colorado9 and had no history of travel.
The cat had no intraocular mass and no blood work or thoracic radiograph abnormalities that suggested neoplasia. Because the
uveitis was bilateral and the patient had mild lethargy and lymphocytosis, the cause was likely to be idiopathic, immune-mediated,
or a manifestation of a systemic disease such as an infection.
The patient was anesthetized, and anterior chamber paracentesis was performed. Atraumatic tissue forceps were used to grasp
the bulbar conjunctiva, and a 27-ga needle was inserted through the perilimbal conjunctiva and limbal cornea to aspirate a
small amount of aqueous humor.1 PCR testing was done on the aspirate to evaluate for fip infection and bartonellosis.
In addition, serum was submitted for protein electrophoresis to distinguish between a monoclonal and polyclonal gammopathy
as a cause of the cat's elevated globulin concentration. A polyclonal gammopathy is expected in patients with inflammatory
or infectious conditions, especially chronic infections, toxoplasmosis, or FIP infection. A monoclonal gammopathy is consistent
with some types of neoplasia, such as multiple myeloma. Serum was also submitted to evaluate the cat's antibody titer against