Tumor of the Eye (Ocular Cancer) in Dogs

Cancers of the eye are rare in dogs. The severity of the condition depends on whether the tumor is benign or malignant.

Some tumors begin development inside the eye, and cannot initially be seen. By the time a tumor becomes visible the cancer may have already progressed to a later stage, further impacting prognosis.

Uveal melanomas tumors are the most common eye tumors to affect dogs. They typically originate in the iris, and are usually (but not always) benign.

Ciliary body adenomas (benign) and adenocarcinomas (malignant) tumors are the second most common. The ciliary body is behind the iris and not visible to the naked eye, however as cancerous cells proliferate a tumor becomes visible.

All tumors require prompt veterinary assessment. Early diagnosis and treatment provide the best chance of a positive outcome.

Ocular tumors are rare in dogs. They can be benign, developing slowly and not spreading from the eye, or malignant, developing quickly and spreading throughout the body, destroying other tissue in the process. The prognosis for malignant tumors is guarded, and these cases may be fatal.

Tumors can also result in secondary ocular conditions, such as glaucoma or uveitis.

A dog affected by malignant tumors may present with more general symptoms of serious illness.

Ocular tumors are usually unilateral in dogs so vision loss is not immediately noticeable.

Genetics, retroviruses, and UV exposure can all influence cancer susceptibility, but cancer cannot be described in a simple ‘cause to effect’ correlation.

Cancer is more common in middle-aged to older, mature dogs. Some breeds are more susceptible to certain kinds of tumor than others, such as pale-eyed dogs being susceptible to spindle-cell tumors.

Cancer may develop due to environmental or genetic factors, but the cause is often unknown.

There are a variety of primary ocular tumors, including:

• Mast cell tumor (which are not exclusive to the eye)
• Neuroectodermal tumors
• Schwannomas of blue eyed dogs

Secondary ocular tumors occur when tumor cells from cancer elsewhere in the body spread to the eye.

The most recognizable symptom of an ocular tumor is a growth or mass developing in the eye. It can appear over or under the iris and pupil, depending on the type of tumor. Tumors present in a variety of opaque colors: black, yellow, green, red, or as multicolored splotches.

Diagnostic imaging helps establish the general health of the dog, and determine the stage of the cancer. A biopsy determines the type of tumor. Blood tests may be indicated, and referral to a specialist (oncologist or ophthalmologist) may be beneficial.

Treatment varies depending on the type of tumor. Sometimes it is possible to remove the tumor itself, or treat it with minimally-invasive laser eye surgery or chemotherapy. Other times removal of the eye provides the best chances for recovery.

Ocular tumors are lifelong, and their prognosis is variable to poor. In some instances the cancer can recur, even after successful treatments.

Eye removal is commonly indicated, which may remove all of the cancer cells but results in loss of vision. Fortunately, a dog can still live a full and healthy life, even with reduced vision.

Secondary tumors and other malignant cancers have a far more guarded prognosis, and may be fatal, even with aggressive treatment.

Early identification and treatment provides greatest chances for a positive outcome. Ocular tumors are not contagious.

Ocular cancer is rare in dogs.

• Eye removal
• Tumor removal
• Laser eye surgery
• Chemotherapy