Rhea V. Morgan, DVM, DACVO, DACVIM
Anterior uveitis is inflammation that affects the iris and ciliary body (anterior uvea) of the eye. If the posterior uvea is also involved the inflammation is termed panuveitis. The causes of anterior uveitis are numerous and it can be difficult to diagnose the underlying etiology. Although some causes are confined to the eye, in many cases the condition is a symptom of a multisystemic disease. Thus, the animal may present with predominately ocular signs or with only multisystemic signs.
DIAGNOSIS OF ANTERIOR UVEITIS
ETIOLOGY AND RISK FACTORS
- Systemic Infectious Diseases are amongst the most common causes of anterior uveitis
- Viral diseases - Feline immunodeficiency virus (FIV), feline leukemia virus (FeLV), feline infectious peritonitis virus(FIP), canine distemper and canine adenovirus.
- Fungal diseases - Blastomycosis, histoplasmosis, cryptococcosis, coccidioidomycosis, candidiasis. Certain fungi are more common in dogs (blastomycosis, coccidioidomycosis), while others are more common in cats (histoplasmosis, cryptococcosis).
- Protozoal diseases - Toxoplasmosis (primarily cats), leishmaniasis (primarily dogs), and possibly neosporosis in dogs.
- Rickettsial diseases - Ehrlichiosis and Rocky Mountain spotted fever in dogs.
- Bacterial infections - Septicemia and bacteremia; brucellosis, leptospirosis and borreliosis in dogs; possibly Yersinia in cats.
- Algal infections - Protothecosis in dogs
- Parasitic infestations - aberrant nematodal larval migrans, ophthalmomyiasis interna.
- Parasitic infestations - aberrant nematodal larval migrans, ophthalmomyiasis interna
- Canine adenoviral vaccinal reactions (rare)
- Uveodermatologic Syndrome (Vogt-Koyanagi-Harada-like syndrome, VKH) - An anti-melanocyte disease that affects the eyes, skin and hair coat, especially in Arctic sled dog or Oriental dog breeds (e.g. Akita, Siberian husky, Samoyed, Malamute, chow chow, Shetland sheepdog).
- Associated with other immune-mediated diseases, including thrombocytopenia, hemolytic anemia, etc.
- Neoplasia (both primary and secondary tumors) may cause anterior uveitis.
- Lymphoma - More common in cats than dogs, usually a component of a multicentric lymphoma.
- Melanoma - Occurs in both dogs and cats; is usually a discrete mass in the iris of the dog, but may produce diffuse changes in the iris of the cat.
- Adenoma/Adenocarcinoma - Primary tumors arise in the ciliary body; secondary tumors are metastatic from distant sites.
- Metastatic tumors - They consist of both carcinomas and sarcomas because the uveal tract behaves as both a vascular and lymphoid tissue for the eye.
- Other Causes of uveitis include the following:
- Lens-induced uveitis - It occurs when the eye is exposed to sequestered lens proteins. Phacolytic uveitis develops when hypermature cataracts leak protein into the eye. Phacoclastic uveitis occurs with penetrating injuries to the lens.
- Trauma - Any type of injury to the head or eye can cause uveitis, and uveitis may sometimes accompany generalized trauma.
- Metabolic diseases and blood dyscrasias - Uveitis associated with these conditions may arise due to breakdown of the blood-aqueous barrier. Examples include diabetes mellitus, hyperlipidemia, hypertension, hyperviscosity, polycythemia, bleeding disorders, uremia, pancreatitis, etc.
- Idiopathic forms - Anterior uveitis is called idiopathic when an exhaustive systemic workup fails to reveal an underlying cause. Idiopathic uveitis occurs frequently in the cat and sporadically in the dog.
- Breed-specific uveitis - Golden retrievers are prone to a peculiar pigmentary uveitis that is frequently accompanied by iris cysts and secondary glaucoma.
- Secondary uveitis - Any inflammation, injury or disruption of other ocular tissues can result in secondary uveitis. Examples include serious corneal ulcers and injuries, radiation therapy, intraocular surgery, acute glaucoma, posterior segment hemorrhages, etc.
- Risk factors - vary widely due to the various underlying causes of uveitis.
- Age - Older animals are more likely to have metabolic diseases, lens-induced uveitis and tumors.
- Breed/genetics - Golden retrievers are prone to pigmentary uveitis. The Akita, Siberian husky, Samoyed, Malamute, chow chow and Shetland sheepdog are prone to VKH Syndrome.
- Sex - Older male cats are more likely to have idiopathic uveitis or uveitis associated with FIV.
- Geographic/environmental - Indoor/outdoor pets are more likely to be exposed to infectious diseases than animals housed strictly indoors. Certain infectious diseases are more common in certain regions of the world.
- Prevention - Cats are protected from many of the infectious diseases that cause anterior uveitis by housing them only indoors. Many causes of uveitis are not preventable.
HISTORY AND CLINICAL SIGNS
- Species affected - Dogs and cats
- Presenting signs and historical problems - Frequent complaints cited by the owner include redness of the eye, epiphora, squinting, photophobia, and cloudy appearance to the eye.
PHYSICAL EXAMINATION FINDINGS
- Attitude - The systemically ill or injured animal may be lethargic and depressed. Most animals with anterior uveitis are bright and alert.
- Body condition - The body condition is usually normal unless the animal is chronically ill with a systemic disease.
- Vital signs - The vital signs are often normal
- Ophthalmic examination
- Findings associated with Acute Uveitis - Conjunctival and episcleral hyperemia, epiphora, squinting, photophobia, miosis or an unevenly shaped pupil, discoloration and/or thickening of the iris, aqueous flare, corneal edema, low intraocular pressure (IOP).
- Findings associated with Chronic Uveitis - Keratic precipitates, posterior synechiae, glaucoma (elevated IOP), secondary cataracts, hyperpigmentation of the iris, inflammatory debris on the anterior and/or posterior lens capsule, cloudiness in the vitreous.
- Other associated Ocular Findings - Iris cysts in golden retrievers, depigmentation of the iris and posterior uvea with VKH Syndrome, diffuse or focal mass-like lesions of the iris and ciliary body with neoplasia, posterior uveal chorioretinitis lesions with many of the fungal, protozoal and algal diseases, hyphema or posterior segment hemorrhages with trauma, hypertension, hyperviscosity or polycythemia, retinal detachments, and secondary blindness.
- Systemic Examination
- A thorough physical examination is indicated in all animals presenting with anterior uveitis.
- All body systems are examined for abnormalities that may indicate an underlying systemic disease and to identify unrelated illnesses that must be take into consideration when designing a treatment plan for the animal.
- Special examination techniques
- Measure blood pressure if hypertension is suspected
- Bone marrow aspiration is indicated if there is evidence of blood dyscrasias on the CBC, or if lymphoma is suspected in the iris.
- A serum protein electrophoresis is indicated to better characterize any hyperproteinemia present.
- Clinical laboratory tests - A routine database is acquired consisting of a CBC, biochemistry profile and urinalysis
- CBC - The results of the CBC vary and are often normal. Possible abnormalities include evidence of anemia (low RBC count), evidence of systemic inflammation or bacterial infection (high WBC count), evidence of viral infection (low WBC), platelet abnormalities with rickettsial infections and immune-mediated conditions, high RBC count with polycythemia, etc.
- Serum biochemical tests - The results of the biochemical profile vary depending on the underlying cause of the uveitis and is often normal. Some animals may have evidence of renal or hepatic disease, diabetes mellitus, hyperproteinemia, elevated bilirubin, etc
- Urinalysis - Often unremarkable but may reveal isosthenuria and casts with renal disease, elevated specific gravity with dehydration, crystals and an active sediment with urinary tract infection.
- Coagulation profile - Consider submitting a coagulation profile if there is evidence of non-traumatic ocular or systemic bleeding, or a low platelet count on the CBC
- Serology/immunologic tests - The choice of serologic tests is determined by the infectious diseases endemic to the geographic region in which the animal lives or has traveled.
- Test all cats for FeLV, FIV, FIP and toxoplasmosis. Also consider an assay for cryptococcosis.
- Consider assays for the fungal diseases, toxoplasmosis, leptospirosis and the tick borne diseases in dogs.
- Aqueous humor may also be submitted for serologic assays of toxoplasmosis-induced immunoglobulin in cats.
- Parasitology - Fecal examination is recommended to determine if concurrent gastrointestinal parasites are present.
- Blood and urine are cultured if there is evidence of septicemia or bacteremia.
- Cerebrospinal fluid may be aspirated for cytology and culture if CNS signs are also present
- Diagnostic imaging
- Radiographs (thoracic/abdominal) - Thoracic and abdominal radiographs may reveal evidence of fungal infection, pneumonia, pleural effusion, anterior mediastinal or pulmonary neoplasia, systemic trauma, etc.
- Ultrasound (abdominal) - An abdominal ultrasound is recommended to detect abdominal masses or other abnormalities.
- Ultrasound (other) - An ultrasound of the eye may be performed if the posterior segment cannot be visualized in order to rule out neoplasia, retinal detachments, movement of the lens, etc.
- CT/MRI - Advanced imaging is rarely performed in cases of uveitis and is usually reserved for those instances in which central nervous system disease is suspected
- Cytology (fluid or tissue) - Fine needle aspirates may be helpful. Consider aspirating or making impression smears of any cutaneous draining lesions or masses. Aspiration of aqueous humor is not often done, but may be helpful to detect the presence of neoplastic cells. When the eye is blind and the posterior segment is also involved, a vitreal cavity aspirate may be considered.
- Biopsy/histopathology - Biopsies of masses, abnormal lymph nodes, and other tissues may be submitted for histopathology. Certain diseases, such as protothecosis and histoplasmosis may be diagnosed on endoscopic biopsies taken from affected areas of the large intestine. Biopsies of primary tumors identified on radiography or ultrasonography may yield a histologic diagnosis for metastatic lesions to the eye. Skin biopsies help to identify VKH Syndrome.
DIAGNOSIS AND PROGNOSIS
- Differential diagnosis
- Other causes of epiphora and photophobia: corneal ulcers, corneal foreign bodies, glaucoma, anterior lens luxation, penetrating injuries.
- Other causes of anisocoria: Horner's syndrome, defects of the iris and iris sphincter, neurologic problems.
- Other causes of a cloudy anterior ocular medium: corneal edema, corneal infiltration with lipid or calcium, corneal scarring, cataract.
- Other causes of alterations in IOP: glaucoma.
- Recommended tests - The recommended tests will vary for case to case and may include CBC, biochemical profile, urinalysis, radiographs, serology, etc.
- Summary of diagnostic criteria - The results of the diagnostics tests vary as discussed above.
- Prognosis -Varies depending upon the cause
- Fungal, algal infections - fair
- Viral infections - fair to good with long-term therapy; secondary glaucoma is common
- Bacterial infections - fair to good
- Rickettsial infections - good
- Protozoal infections - fair to good with long-term therapy
- Phacolytic uveitis - good
- Phacoclastic uveitis - fair to poor
- VKH Syndrome - fair to poor
- Idiopathic uveitis - good with long-term therapy
- Golden retriever uveitis - fair; secondary glaucoma is common
- Neoplasia - guarded
- Trauma - fair to good
- Secondary uveitis - good if underlying problem is treatable
TREATMENT OF ANTERIOR UVEITIS
Therapy of anterior uveitis involves treatment of the specific underlying cause, and treatment of the ocular disease itself.
- Treatment of the ocular disease
- Anti-inflammatory therapy
- Topical therapy - requires the use of corticosteroids that penetrate into the anterior chamber or the use of nonsteroidal anti-inflammatory agents (NSAIDs).
- Corticosteroids - Dexamethasone, betamethasone, prednisolone phosphate, or prednisolone acetate are given 2- 12 times daily, depending upon the severity of the inflammation.
- NSAIDs - Flurbiprofen, diclofenac, indomethacin, suprofen are administered 2-4 times daily, especially if corticosteroids cannot be given due to the presence of a corneal ulcer. NSAIDs are contraindicated if the IOP is elevated.
- Systemic therapy - subconjunctival or parenteral medications.
- Subconjunctival steroids - Methylprednisolone acetate or triamcinolone 4-8 mg may be given if there are no infectious agents present in the anterior chamber.
- Oral nonsteroidal agents - Buffered aspirin (10mg/kg PO BID) or carprofen (2 mg/kg PO BID) are used in dogs, and baby aspirin 6 mg/kg PO q 48-72 hours is given to cats.
- Oral prednisone - It is given at 0.25 - 0.5 mg/kg Po BID only if underlying infectious agents have been ruled out.
- Mydriatic/cycloplegic therapy - These are used to relax the iris sphincter and relieve pain, and to prevent posterior synechiae.
- Cycloplegics include the parasympatholytics, atropine and tropicamide. Atropine 1% is the most common cycloplegic used and is given 2- 6 times daily. Tropicamide 1% is very short-acting and is used primarily when IOP is elevated.
- Other mydriatics include the active pupil dilators (sympatho-mimetics) that are synergistic with the cycloplegics. Phenylphrine 2.5% is administered 3 to 4 times daily. Epinephrine 1% is administered 3 to 4 times daily.
- Medical therapy of the primary cause
- Protozoal Diseases - Clindamycin
- Fungal and Algal Diseases - Itraconazole
- Tick borne Diseases - Doxycycline
- Bacterial Infections - Appropriate antibiotics
- Uveodermatologic Syndrome - immunosuppressive dosages of prednisone, with or without cytoxic agents such as azathioprine
- Lymphosarcoma - various chemotherapeutic protocols
- Surgical therapy - Indications/Options
- Neoplasia within the eye - enucleation
- Phacoclastic uveitis - lens removal
- Uveitis unresponsive to therapy, especially with secondary conditions such as blindness or glaucoma - enucleation
- Eye is a nidus of persistent infection (e.g. fungal infections) - enucleation
Frequent rechecks are generally necessary to adjust medications and monitor progression of the disease. Initially, recheck examinations may be needed as frequently as once or twice a week until the condition is stabilized. Eventually rechecks are decreased to once or twice monthly, and are often continued for several months. Medical therapy is often required for several months to bring the ocular changes under control.
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