INTRODUCTION
Uveitis is the inflammation of the vascular coat of the eye. It is a common presenting sign in canine and feline ophthalmology. It is classified into three categories: 1) anterior (inflammation of iris and ciliary body); 2) intermediate (ciliary body, pars plana); and 3) posterior (choroid) uveitis. Early recognition and immediate control of inflammation are essential to avoid irreversible complications such as glaucoma, cataract and blindness. The cause of uveitis should next be identified if possible.
Clinical diagnosis
The diagnosis is based on clinical findings of active uveitis, recognition of complications and elements of differential "red-eye" diagnosis.
Clinical signs
Redness (episcleral reddening)
Ocular pain (watery discharge, blepharospasm, photophobia, enophthalmos)
Corneal changes (edema, deep vascularisation)
Anterior chamber changes (aqueous flare, keratic precipitates, hyphema, hypopyon)
Iris changes (in colour, swelling, granulomas)
Myosis
Low intra ocular pressure
Lens anomalies (deposits, cataract)
Vitreous flare
Fundus anomalies
Differential diagnosis
Differential diagnosis must include consideration of other acquired ocular conditions (conjunctivitis, corneal diseases, KCS, glaucoma, tumors) and of developmental conditions (aniridia, heterochromia, persistent pupillary membrane, cysts).
Complications
Complications of anterior uveitis are: synechiae (adhesion of the iris to contiguous structures), secondary glaucoma (hypertensive uveitis), iris atrophy, corneal edema (secondary to endothelial damage), lens subluxation/luxation, cataract (in cats), fundus changes, panophthalmitis, phthisis bulbi.
Aetiological diagnosis
Examination and History
After a complete ocular examination (both eyes) a thorough general examination is not to be neglected. Precise questions should be asked in taking a history (age, vaccination, environment, trauma, travels) combined with epidemiological considerations.
Additional examinations
Imaging: Head radiographs are indicated in cases of unilateral uveitis. Chest and abdominal radiographs may reveal major organs abnormalities. Ocular Ultrasound is useful in cases of media opacity.
Blood samples: A conventional laboratory profile should include a blood count, protein electrophoresis (hyperglobulinaemia in chronic "parasitic" diseases and FIP, FIV), a biochemical profile and serological screening tests when available.
Aqueous humor samples are useful to demonstrate local antibody production, for cytology and Polymerase Chain Reaction (PCR).
Conjunctival samples are useful for cytology, cultures, direct parasite observation and PCR
Causes of Canine Anterior Uveitis
Unknown-Idiopathic
Trauma (accidental and surgical)
Viral: Hepatitis, Distemper
Bacterial: Corneal wounds, Bacterial sepsis (e.g., pyometra, dental disease), Leptospirosis, Borreliosis, Brucellosis, Tuberculosis
Protozoal: Leishmaniasis, Neosporosis, Toxoplasmosis
Parasitic: Dirofilariasis, Angiostrongylosis, Toxocariasis
Rickettsial: RMSF, Ehrlichiosis
Fungal/Algal: Blastomycosis, Histoplasmosis, Coccidioidomycosis, Cryptococcosis, Protothecosis
Immune mediated: Lens induced uveitis, uveodermatologic syndrome
Metabolic: Hyperlipidemia, Diabetes Mellitus
Genetic: Uveitis in Golden Retrievers associated with iridociliary cysts
Neoplasia
Causes of Feline Anterior Uveitis
Unknown--Idiopathic
Trauma
Viral: FIP, FeLV, FIV, FHV-1
Protozoal: Toxoplasmosis, Leishmaniasis?
Bacterial: Corneal wounds, Tuberculosis, Bartonellosis, Borreliosis
Fungal: Cryptococcosis
Hypertension: intra ocular haemorrhages (+/- retinal detachment)
Neoplasia
Treatment
Mydriatic: Atropine 1% applied 4 times daily.
Corticosteroids
Topical: Prednisolone or Dexamethasone can be used (contraindication: ulcerative or mycotic keratitis). Both of these products have a good penetration into the eye.
Subconjunctival: Triamcinolone acetonide or Methylprednisolone acetate (0,2 ml) provide anti inflammatory activity for at least 2 weeks.
Systemic corticosteroids: Prednisolone or Prednisone can be used (immunosuppressive dosage: 1mg-2 mg/kg per os BID). When inflammation is under control, the dosage is reduced gradually.
Non Steroidal Drugs (NSAIDS)
Topical: Flurbiprofen, Suprofen, Diclofenac, Indomethacin can be used.
Systemic NSAIDS: These are an excellent choice for treating intra ocular inflammation at the same time avoiding the side effects of steroidal drugs. Flunixin meglumine, Carprofen, Ketoprofen, Tolfenamic acid (Inject 4 mg/kg) are all efficient products.
Immunosuppressive drugs: Systemic Azathioprine, or Cyclosporine may be used in case of unresponsive uveitis. Patients need to be monitored for their side effects. Topical cyclosporine is not efficient in the treatment of intra ocular inflammation.
Specific treatment: If the cause is found, specific medical therapy (antibiotics, antifungals, antiparasiticides) are administered combined with the anti inflammatory therapy. Surgery might be advised to eliminate focal infections.
Practical strategy: Always follow a strict protocol
1. Diagnosis of uveitis on clinical findings
2. Control inflammation immediately (strike hard). Begin with topical atropine, topical and subconjunctival corticosteroids, always combined with systemic NSAIDS or SAI DS.
3. Ascertain the cause (take a history, perform an ophthalmic and general examination, perform complementary tests)
4. Add specific treatment in cases where the cause is found
Conclusion
New laboratory techniques and new drugs such as NSAIDS can now help the veterinarian to recognize and control uveitis more efficiently.