Uveitis is an inflammatory process of the vascular portion of the eye, the uvea. This is made up of the iris, which makes eye our color blue, brown, green, etc., the ciliary body, which produces fluid (aqueous humor) to provide nourishment to the avascular cornea and lens, and the choroid, which nourishes the retina and the back part of the eye. If left untreated uveitis can lead to blindness, sometimes very quickly.
Diagnosis of Uveitis In general, a pet with uveitis may produce signs such as redness, squinting, watery discharge and photophobia (sensitivity to light). The clear cornea may become cloudy making structures inside the eye difficult to see. Inside the eye there may be blood or cloudy material made up of inflammatory cells and fibrin, abnormal pupil size or shape, and altered iris color.
The causes of uveitis are numerous and diagnostic testing can become involved and be complex. Sometimes, as with humans, the diagnosis may be difficult to determine, i.e. idiopathic. This does not mean it cannot be treated symptomatically. The eye is often termed the window to the soul, and Dr. Gwin may be able to diagnosis a generalized or systemic disease by examination of the rear portion of the eye termed the fundus or posterior segment. This would include fungal infections, hypertension, parasitic infestation, viral infection, and lymphoma to name a few. Ocular examination of the front part of the eye (iris, anterior chamber, lens, and cornea) is performed with a slit lamp and the measurement of ocular pressure. High intraocular pressure is glaucoma and tells us the “drain” or outflow is compromised. If the internal structures of the eye cannot be visualized, ocular ultrasound may be performed to more clearly define the position of the retina and lens and to detect any abnormal masses or growths within the eye. Hopefully, with proper medical therapy and a good response, the inflammatory disease will be controlled. However, recurrence is always a possibility as is the persistence or recurrence of glaucoma. Many times pets (and people) have to be on a low dose of long term medical therapy (usually topical) to keep this inflammatory disease at bay.
Additionally, disease processes such as uveitis can lead to corneal erosion or ulceration, scarring, cloudy (cataract) or displaced (luxated) lens, retinal detachment or degeneration.
Causes of Uveitis are associated with many different diseases. Examples in the dog include tick born diseases (Ehrlichiosis, Rocky Mountain spotted fever), histoplasmosis (fungus), and lymphoma (cancer of the white blood cells). In the cat, uveitis can be associated with Feline Leukemia Virus (FeLV), Feline Infectious Peritonitis (FIP), Toxoplasmosis, and several other disease processes.
Cataract Induced Uveitis is included as a separate category due to the frequency of cataract induced uveitis seen in pets, and more frequently dogs with diabetes. As cataracts become mature or hypermature they release liquefied proteins through their lens capsule (or bag). This protein is foreign to the immune system, which then attacks the eye. This inflammation can cause irreversible damage, sometimes very quickly. It can also frequently be prevented or controlled with proper medical therapy prior to the cataract removal. Early is better. In more advanced cases vision is permanently lost and the eye may need to be removed.
Uveitis must be treated aggressively in order to prevent or control cataract formation, retinal detachment, etc. Therapy is somewhat complex depending on many factors. Antibiotics, anti inflammatory medications (corticosteroids, NSAID’s) pressure medication, is given topically and/or orally to combat the disease. This can be complicated, but something Dr. Gwin has dealt with daily for many years.