Tumors of the Anterior Uvea (Iris and Ciliary Body) in Dogs
Dr. Noelle McNabb
Veterinary care includes a variety of diagnostic tests and subsequent treatment recommendations, as outlined below. A complete history and thorough physical examination, including palpation for enlarged lymph nodes, and swollen, enlarged or irregularly shaped abdominal organs. Your veterinarian will listen to the chest with a stethoscope to determine whether the heart and lung sounds are normal. When tumors or fluid accumulate in the chest, these sounds are often muffled.
Diagnostic tests are performed to determine if the anterior uveal tumor is confined to the eye or if other organs or body cavities are affected with tumor. The results of these tests help define what is the most appropriate treatment. These tests may include:
Complete ophthalmic examination including testing of pupillary light reflexes, Schirmer tear test, fluorescein staining of the cornea, tonometry to measure the pressure within the eye, and examination of the interior of the eye under magnification. Your veterinarian may refer your dog to a veterinary ophthalmologist for further evaluation using specialized instrumentation.
Gonioscopy, a specialized test to examine the area in the front of the eye where fluid leaves the eye. This helps to determine if the uveal tumor is extending into and/or obstructing this drainage angle.
Ocular ultrasound to delineate the boundaries of the intraocular tumor. It is also useful to determine if retinal detachment or lens displacement has occurred and may help to determine if the tumor extends behind the eye.
Aqueocentesis (a fluid sample taken from the anterior chamber of the eye) and fine-needle aspirate of the uveal mass may be useful in distinguishing certain infections (fungal, protozoal, parasitic) from a cancerous process.
Routine blood work (complete blood count, serum biochemistry) and urinalysis are usually done to assess function of other organs.
Bone marrow aspirate and cytology may be done if lymphosarcoma or other bone marrow cancers are suspected.
Chest X-rays are usually taken to search for masses or tumors, enlarged lymph nodes, and fluid in the chest.
Abdominal X-rays may be taken to search for organ enlargement, masses and enlarged lymph nodes in the abdomen. These X-rays may be followed by an abdominal ultrasound if any abnormalities are discovered.
Computerized tomography (CT) or magnetic resonance imaging (MRI) may be used to examine the eye, orbit, optic nerve and brain. These tests are most useful if extension of the uveal tumor into the orbit or brain is suspected.
Treatment of anterior uveal tumors may be divided into either medical management or surgical therapy. Eyes with primary uveal tumors that are amenable to complete surgical excision may require medical therapy following surgery. In the early stages of uveal tumor development, clinical evidence of eye discomfort or irritation is often not evident. Invariably, as uveal tumors enlarge, they result in inflammation (uveitis) and secondary glaucoma, and the eye may become painful.
Medical treatment alone is not enough to treat primary anterior uveal tumors. Typically, the inflammation caused by the tumor expansion within the eye does not respond well to medical therapy.
In early stages of uveal lymphosarcoma (a metastatic or secondary tumor), chemotherapy may induce regression of the tumor and the dog may go into remission. However, eyes that develop secondary glaucoma from advanced lymphosarcoma may not respond as well to chemotherapy and may remain painful and blind.
Response to medical treatment for all other secondary uveal tumors is generally poor and ultimately most of these tumors require that the eye be surgically removed (enucleated).
For small iris tumors, the tumor and part of the iris (iridectomy) may sometimes be removed surgically. Some darkly colored tumors may also be treated with a diode or Nd-YAG laser. Both of these procedures have some potential serious side effects and are applicable to only a small number of iris tumors.
Most anterior uveal tumors are too large and extensive to remove surgically, so removal of the eye is usually necessary. Quite often these eyes are painful due to secondary glaucoma, uveitis, or hyphema.