January 30, 2019
In January’s Pulse article, Dr Esson discusses common uveal diseases in small animals. The uveal tract is composed of anterior and posterior tissues. These tissue’s contain components of “blood ocular barrier” which regulates the passage of protein into the aqueous humor. Some very common clinical presentations are infectious, inflammatory, metabolic, and neoplastic disease. To read more, click on the Pulse article link:
The uveal tract is composed of anterior (iris & ciliary body) and posterior (choroidal) tissues. These tissues contain components of the “blood-ocular barrier” which regulates the passage of protein into the aqueous humor. Relatively common clinical presentations associated with uveal tissues encompass infectious, inflammatory, metabolic & neoplastic disease.
Uveal cysts (“iris cysts”) may arise from the posterior iridal or ciliary body epithelium, commonly affecting the Labrador Retriever, Golden Retriever, Boston Terrier, Great Dane & American Bulldog. Most uveal cysts are benign and do not require treatment. Additionally, the presence of uveal cysts has been associated with elevated intraocular pressure in some breeds including the American Bulldog & Great Dane. Surgical intervention may be indicated in cases where cystic proliferation results in visual impairment and/or compromised aqueous outflow.
The term uveitis describes inflammation of any of the uveal tissues and is typically associated with variable breakdown of the blood-ocular barrier. Bilateral uveitis should prompt concern for the presence of systemic disease. Potential etiologies include hereditary factors, lens-associated inflammation trauma, systemic disease, exposure to infectious organisms and/or the presence of (local or systemic) neoplasia. Infectious etiologies which may be associated with the development of anterior uveitis in cats include; viral (FelV, FIV, FIP, FHV), protozoal (Toxoplasma gondii), bacterial (notably Bartonealla spp) and fungal (crytococcus, cocciodiomycosis, aspergillus, blastomyces & histoplasmosis) organisms. Infectious etiologies which may be associated with the development of anterior uveitis in dogs include; viral (canine adenovirus-1 & canine parvovirus), protozoal (Toxoplasma gondii), bacterial (notably Erlichia canis, Rickettsia rickettsia, Leptospira spp & Borellia spp) and fungal (cocciodiomycosis, aspergiullus, blastomyces & histoplasmosis) organisms. Frustratingly, the etiology of uveitis remains unclear in a significant proportion of cases. Treatment encompasses addressing underlying systemic, infectious or neoplastic disease, as well as the administration of topical and/or systemic anti-inflammatory therapy. Long-term treatment may be indicated in order to minimize the risk of secondary glaucoma.
A syndrome comprising slowly progressive intraocular changes, typically culminating in secondary glaucoma, is well recognized within the Golden Retriever breed (already briefly described in a previous review of conditions affecting the uveal tract). This syndrome has been variably described as “Pigmentary Uveitis”, “Golden Retriever Uveitis” and “Pigmentary & Cystic Glaucoma of Golden Retrievers”. Initial symptoms (comprising ocular redness, anterior pigment dispersion, cataract formation and/or IOP elevation) are frequently noted around middle age and are usually bilateral, although not necessarily symmetrical. Treatment is generally empirical, frequently comprising topical and/or systemic anti-inflammatory immune-modulating as well as IOP-lowering agents, however secondary glaucoma is frequently the end-point of this disease.
Canine uveodermatologic syndrome represents an immune-mediated disease affecting melanocytic tissue and exhibits similarities to Vogt-Koyanagi-Harada (VKH) disease in humans. Ocular symptoms include anterior uveitis, chorioretinitis or panuveitis. Additional symptoms may include any combination of periocular, mucocutaneous oral and/or nasal viteligo (loss of pigment), poliosis (whitening of hair) and/or ulcerative dermatitis. Typically these symptoms are relatively bilaterally symmetrical in appearance. Commonly affected breeds include the Akita, Siberian Husky, Samoyed & Chow Chow. Treatment usually comprises aggressive, longterm anti-inflammatory and/or immune-modulating therapy, with successful management typically achievable.
Aqueous lipidosis describes a condition in which elevated levels of lipoproteins move into the anterior chamber. Changes may occur spontaneously as a result of primary hyperlipoproteinemia, following significant dietry indiscretion, in association with underlying metabolic disease and/or as a result of anterior uveitis. Addressing underlying metabolic and/or dietary imbalances as well as concurrent uveitis, if present, typically results in rapid resolution of symptoms. In selected cases, treatment using fibrates (such as gemfibrozil) and/or statins (such as atorvastatin) may be indicated, however the use of these products in canine patients has not been approved.
Feline diffuse iris melanosis (FIDM) comprises the accumulation of pigmented melanocytes within the anterior iridal tissue. With time, some cases display deeper iris invasion and may additionally develop histologic characteristics of malignancy, representing true iris melanomas. The management of iris melanosis (& its differentiation from iridis melanoma) represents a challenge to the practitioner. Options include;
- clinical monitoring only (particularly relevant in cases displaying only minimally progressive focal nevi which are not elevated above the level of the iris)
- laser photoablation of affected tissues (particularly relevant in cases showing relatively rapid progression or beginning to invade ICA structures)
- enucleation (particularly relevant in cases displaying changes suggestive of outright uveal neoplastic progression and/or secondary glaucoma). Clinical changes suggestive of neoplastic proliferation may include the development of “velvety” appearance to focal areas of pigmentation, followed by obvious elevation of pigmented tissue above the iridal surface and resultant pupillary dyscoria
Other relatively commonly encountered neoplastic processes which may affect the uveal tract include lymphoma, melanoma & adenocarcinoma. These may be managed via chemotherapeutic intervention where indicated, surgical resection where possible or enucleation if necessary.
Dr Esson is a board-certified veterinary ophthalmologist with more than twenty years of clinical experience and multiple areas of interest & expertise. His clinic Veterinary Ophthalmic Consulting (www.veterinaryophthalmicconsulting.com) is family owned & operated and he takes great pride & pleasure in working closely with his friends and colleagues in the greater Southern California veterinary community.