Uveal Diseases in Dogs and Cats

Uveal Diseases in Dogs and Cats

What the UVEA?
The uvea includes the iris, ciliary body and the choroid, which are all intraocular structures in close proximity with one another, and so are grouped together as a collective term in their anatomical description.

What is a UVEA Cyst?
A uveal cyst is a hollow structure associated with the iris or the ciliary body. These cysts are often darkly pigmented, and observed in adult dogs. These cysts can either be congenital (ie present since birth) and only noticed as an adult, or can occur after local inflammation within the eye. These cyts can either be adhered to a part of the uvea, or can be free floating within the eye.

What is the issue with UVEA Cyst?
Uveal masses are usually benign cysts, however it is crucial that this is assessed by a specialist veterinary ophthalmologist as it may be a cancerous change within the eye. Although benign, large cysts can cause vision impairment, damage and impairment of function to various eye structures, and obstructing the normal fluid flow throughout the eye. For this reason we recommend surgical removal of cysts in many cases.

What is a UVEA Tumour?
Although most uveal masses are benign, a proportion of them are malignant masses that have the ability to leave the eye to enter other sites of the body and cause issues (in up to 10% of cases), or cause local destruction within the eye. These will appear as dark masses on the iris, and may be flat or raised. If it is uncertain if these masses are new, or are growing, then weekly photographs of the eye is appropriate to monitor the mass’ progression.

How are UVEA Tumours treated?
Treatment is surgical, but the exact approach varies based upon the size of the mass, where the mass is located, and the history of the extent of the mass growing. A microsurgical sample can be obtained (via an “iris biopsy) to be sent to the lab to give more information pertaining to the mass. Then, the mass can be irradiated by an external diode laser. This laser “pops” any pigmented cells it contacts, and evokes a local immune response to help remove any residual cancerous cells too. This is the best treatment protocol available for this condition. A proportion of these masses re-grow and may require a second treatment.

What is Uveitis?
Uveitis refers to the inflammation of any tissues that comprise of the uvea. As these structures are the vascular components of the eye, when one of these structures are involved often the others are too. Inflammation of the uvea can change the micro-environment within the eye, and cause many secondary issues within the eye.

What causes Uveitis?
There are many causes of uveitis. This can be from local trauma (both surgical and non-surgical), from infectious causes (algal, bacterial, protozoal, viral and fungal), types of cancers, metabolic diseases (hyperlipidaemia, systemic hypertension), auto-immune conditions, or unknown causes that cannot be determined. In fact, up to half of the cases of uveitis cannot have a cause determined, even if all appropriate diagnostic tests are performed. Uveitis is a painful condition, and can cause many secondary issues within the eye, and if left untreated can cause glaucoma and blindness.

What are the symptoms of Uveitis?
Uveitis can present in many varied ways, however, as a pet owner the most common signs and symptoms will be increased tearing, eye squinting, discomfort in bright lights, a small pupil and a cloudy-appearing eye. Other signs that would be obvious in uveitis include seeing blood or pus present within the eye.

What can be done to treat Uveitis?
As uveitis can result from many different causes, often diagnostic tests will be recommended to try and determine the cause. This is important as although the main clinical signs are within the eye, there may be a much larger and potentially even life-threatening cause underlying these eye issues. While the cause is being investigated, treating the uveitis aggressively is paramount to limit damage to other structures in the eye. This is often performed with potent anti-inflammatory treatment, either orally, topically, or both. Other treatments may be recommended depending on what is seen on examination. Usually, uveitis can be treated very successfully if treated early However, the severity and cause of uveitis will influence the chances of success.