The uveal tract is made up of the iris (colored part of the eye), the ciliary body, and the choroid.  The ciliary body is located behind the iris and produces aqueous humor (the fluid inside the eye).  The choroid is tissue in the back part of the eye that is situated between the inner retina and the outer sclera (the wall of the eye).  Uveal tissue is highly vascular and is responsible for bringing blood flow and nutrition to the internal structures of the eye. 

Uveitis is diagnosed when inflammation develops within the eye.  It is further described based on the location it develops or the tissue it affects:

• Anterior uveitis:  inflammation of the iris and / or ciliary body
• Posterior uveitis: inflammation of the choroid
• Panuveitis:  inflammation of the iris, ciliary body and choroid

When inflammation develops, there is leakage of protein and inflammatory cells into the aqueous humor or other tissues of the eye.  Painful muscle spasms and light sensitivity can also develop causing the animal to rub at the eye and squint or hold the eye closed. 

Causes of Uveitis

Causes of uveitis can include:  

• trauma
• systemic infections - bacterial, viral, fungal, tick-borne illness, abscess
• immune-mediated diseases (complex allergic reactions)
• cataracts - leakage of lens proteins can lead to internal eye inflammation
• in association with other painful eye conditions - corneal ulcers, glaucoma
• intraocular tumor or cancer
• idiopathic - undetermined cause

Diagnosis

Uveitis is diagnosed based on the findings of a detailed eye exam.  Examination equipment that provides magnification, such as a slit lamp biomicroscope or other lenses, assists in viewing the internal eye structures in detail.  The fluid and tissues can be examined microscopically for the presence of inflammation.

The examination should include checking for the presence of a corneal ulcer (fluorescein stain test) and measuring the internal eye pressure (intraocular pressure). 

When the diagnosis of uveitis is made, the cause for inflammation should be determined.  This may be obvious based on other eye problems identified during the exam or it may require other testing (blood and urine tests and x-ray or ultrasound) to determine if a systemic disease or disorder is the root of the problem.  In some instances, a sample of the internal eye fluid may be taken to be examined and analyzed by a pathologist.

Treatment

The underlying cause should be identified and treated.  The affected eye is treated with anti-inflammatory medications (drops or ointments containing a steroid and / or non-steroidal anti-inflammatory) and medications to dilate the pupil.  Dilating the pupil helps to relieve the painful muscle spasms inside the eye and prevents adhesions or scar tissue from developing as a consequence to the inflammation.  An Elizabethan collar should be placed to prevent self-trauma from rubbing of the affected eye.  A warm, moist compress gently applied to the eye for 5 to 10 minutes, several times a day and dimming the lights may also bring comfort to the animal. 

Depending on the severity of the condition, oral medications including anti-inflammatory medications or other drugs to address a systemic illness may also be recommended.  

It is critical to administer the medications as directed.  If uveitis is not aggressively and properly treated, the condition can lead to loss of vision in the affected eye.  While most cases resolve after a course of treatment, other cases may be long standing and require long-term management to keep the condition under control.  

Prognosis

Uveitis is often a painful condition that can generally be controlled or cured with proper treatment.  In some animals, it can be a chronic problem requiring ongoing treatment to keep the condition controlled.

If not properly treated or controlled, it can lead to other problems including glaucoma, cataracts, and retinal detachments - all of which can result in blindness.  In the worst of cases, if the eye loses vision and is considered to be severely diseased or a source of ongoing pain for the animal, surgery may be recommended to remove a blind, painful eye.