by Noelle La Croix, DVM, Dip. ACVO
Uveitis – Diagnosis
The last article in this series described uveitis and some its etiologies. This article will concentrate on the diagnosis and evaluation of uveitis. A final article will be concerned with the treatment and prognosis for uveitis.
A large spectrum of ocular disorders are associated with uveitis. The particularly etiology can sometimes be determined from a patient’s history and physical examination prior to diagnostic testing. Historical background might include environmental factors, adverse reactions to medications, autoimmune disorders, etc. Physical examination will determine if the uveitis is uni- or bilateral; non- or granulomatous, and define its location (anterior, posterior, or pan-). A complete physical examination can also reveal additional signs of underlying inflammatory disease such as swollen lymph nodes, an abdominal mass, or petechiae.
Clinical manifestations of anterior uveitis may include: miosis (a small pupil secondary to the release of prostaglandins), flare (proteins and/or cells that leak into the anterior chamber), redness of the episcleral and scleral vessels (inflammatory cytokines cause vascular dilation and increased blood flow), pain (squinting, blepharospasm, photophobia, and rubbing), low intraocular pressure (from prostaglandin release), and the presence of keratic precipitates (white blood cells and proteinaceous accumulations on the corneal endothelium). Animals with anterior uveitis will usually not present every one of these clinical signs. In addition, secondary manifestations of uveitis (i.e.; synechiae and glaucoma) can make the diagnosis of anterior uveitis particularly confusing. Also note that flare is difficult to access without a slit lamp and if prior anti-inflammatories have taken effect.
In posterior uveitis white blood cells are typically found within the vitreous gel (a condition known as vitritis). Vitritis and lenticular opacities can obscure the fundus preventing its examination without an indirect ophthalmoscope and a high quality lens. Inflammatory cells and serous fluid may also present under or within the retina forming visible lesions. The presence of inflammatory lesions of the ocular fundus are collectively known as chorioretinitis. In cases of acute inflammation these lesions often appear grey-white or yellow-white, or serous (clear) in color and may be associated with small retinal detachments. Perivascular cuffing, retinal edema, and hemorrhage are also commonly associated with chorioretinitis. Severe cases of chorioretinitis can result in complete retinal detachment. The term panuveitis defines inflammation of all layers of the uvea.
Granulomatous inflammatory lesions are an important subset of retinal lesions. The lesions are typically yellow-white in color, nodular, and often elevated. Lesions with a cheese-like appearance (caseous inflammation) indicate some necrosis. Granulomatous uveitis implies that large antigens are trapped within the uvea and can only be removed by macrophages. An opacity of macrophages on the corneal endothelium is known as a “mutton-fat” keratic precipitate.
Uveitis results from ocular and/or systemic disease. Ocular etiologies include corneal ulceration, trauma, cataract formation, and primary cancer. Systemic causes of uveitis include autoimmunity, infection, vascular disease, and systemic neoplasia. It has been established that the root cause of uveitis in young cats and dogs (less than 5 years of age) is typically infection or trauma. In older animals a systemic disease or cancer is the usual cause.
Describing an animal’s uveitis is the first step in establishing the appropriate diagnostic testing. In general a simple case of anterior uveitis will require a CBC and blood chemistry. In addition, dogs should be tested for tick antigens, and cats should be screened for FeLV, FIV, and toxoplasma (with IgG and IgM titers).
Posterior, bilateral, and/or granulomatous uveitis is typically caused by systemic diseases (infection, neoplasia, etc.) that may be refractory to treatment. These cases will often require a wider array of diagnostic tests.
In cases of granulomatous uveitis large antigens from fungi, parasites (heartworms, roundworms, toxoplasma, prototheca, etc.), or viral antigens (FIP) need to be considered. Posterior uveitis with serous retinal detachments are indicative of vasculitis so hypertension, and tick-borne or immune mediated-diseases, should be evaluated for. White blood cells (hypopyon) without corneal ulceration can indicate sepsis and/or lymphoma (Figure 1). Particularly confounding cases may require chest radiographs, abdominal ultrasound, fungal serology, blood pressure evaluation, or other tests. An aspirate of an ocular lesion performed by a veterinary ophthalmologist may be required if diagnostic tests fail to reveal the etiology of a uveitis that is non-responsive to treatment.
Once diagnostics reveal the root cause of an animal’s uveitis, the appropriate treatment can commence to help prevent blindness and/or glaucoma. The treatment and prognosis for uveitis will be covered in the next article in this series. If you have any further questions regarding uveitis, please feel free to consult with a veterinary ophthalmologist.
Noelle La Croix, DVM, Dip. ACVO
Veterinary Medical Center of Long Island
75 Sunrise Highway
West Islip, New York 11795
(631) 587-0800; fax (631) 587-2006
Figure 1: White blood cells (hypopyon) without corneal ulceration can indicate sepsis and/or lymphoma.