Pet Intraocular Tumor

An intraocular tumor is a cancerous growth within the eye.

What are intraocular tumors?

They can arise from normal structures within the eye or can be the result of a tumor that spread from another cancerous site in the body. Tumors can be benign (less aggressive and not likely to spread) or can be malignant (more likely to spread due to their aggressive nature). A tissue sample is often used to make this determination.


What are the clinical signs of intraocular tumors?

The clinical signs of intraocular tumors vary depending on the type of tumor and the structures of the eye affected. Ocular signs may include redness, squinting, cloudiness, the elevation of the third eyelid, ocular discharge, a visible mass inside the eye,  iris color changes, periocular swelling, abnormal deviation of the globe (strabismus), secondary glaucoma (elevated eye pressure), and in some cases,  vision loss in the affected eye.  There may be other systemic signs (such as enlarged lymph nodes, coughing, loss of appetite, etc.) if the tumor is systemic in nature.

There are many different types of intraocular tumors that originate in the eye.  In dogs and cats, the most common intraocular tumor is melanoma. It primarily affects the iris (the colored part of the eye that forms the pupil) initially but can spread to other parts of the eye.  In dogs and cats, iris melanoma usually starts with just a few abnormal spots on the iris.  However, over a few short months to years, it can progress to cause severe changes that can result in pain, loss of the eye, and distant metastasis (spread to another area in the body).  If iris melanomas are caught early in dogs and cats, non-invasive surgical intervention may be available in an effort to prevent further progression (see discussion below).  There are numerous other tumors that can also affect the eyes of dogs and cats.

What causes intraocular tumors?

Often the cause of the tumor is not known.  However, ocular trauma, especially in cats, can result in tumor formation. In other cases, systemic illnesses that cause chronic changes in the eye are the inciting cause of cells transforming into tumor cells.  Due to the numerous causes, it is important to always have a veterinary ophthalmologist evaluate any eye changes or injury to your pet’s eye.

What is the treatment for intraocular tumors?

Treatment is based on the tumor type, the extent of involvement, and the areas involved.  In many cases of early iris melanoma, a non-invasive laser procedure can be performed under general anesthesia in an effort to stop the progression of the tumor.  With some intraocular tumors, advanced imaging (CT scan, MRI, radiographs, or ultrasound) is necessary to determine if other tissues are involved.  If the tumor appears aggressive or is causing severe secondary ocular changes, the eye is often removed and submitted to a histopathologist to determine the tumor type and if additional treatments (chemotherapy, radiation, or additional surgery) are warranted.