About Equine Eye Cancer Tumors

Cancer of the horse's eye can be mild or so severe the eye becomes completely compromised. A veterinarian should be employed to help diagnose the type and severity of the cancer. Cancer of the eye can also cause other problems that will affect the eye and can be quite painful. Occasionally after the cancer has been removed it will return so the area should be observed regularly for abnormal growths. In severe cases the horse may lose the eye completely.

  1. Squamous Cell Carcinoma

    • Squamous cell carcinoma is the most common form of cancer in the eye for horses. It typically affects the conjunctiva around the eye but will occasionally make its way into the eye itself. It usually begins as a small nodule of the conjunctiva but can quickly grow, in some cases taking over the entire ocular area. In instances where the nodule prevents the upper eyelid from closing all the way, other problems like corneal ulcers can occur, causing further irritation. An untreated eye may be compromised to the point that it must be taken out.

    Identification

    • The onset of squamous cell carcinoma is often obvious to the seasoned horseman who has seen it before. A biopsy that can be examined microscopically should be taken to be certain. A fractious or unruly horse, or one suffering eye injury, can be dangerous when approached with a needle near the eye, so sedation restraint should be employed. A thorough exam of the eye and surrounding tissue should be done at this point to see the extent of the cancer's spread and if any other damage has been done to the eye, like an ulcer.

    Treatment

    • As with most cancers, the first form of treatment is generally surgery to remove the affected cells. For smaller tumors this can be done under a local anesthetic in the field but for bigger tumors the horse may need to be taken to the hospital for a full general anesthetic procedure. After the surgery, follow-up treatment may be advised such as cryotherapy, CO2 laser ablation or chemotherapy in the lesioned area. A veterinarian will be able to determine the best course of treatment.

    Reoccurence

    • Like most types of cancer there is a risk of reoccurrence of the cancer. This likelihood increases in at-risk animals, horses lacking pigment in the skin around the eye. Since these horses are more prone to the disease to begin with, they also have a higher rate of reoccurrence. Also, cancer occurs on the cellular level and it is hard to identify every cell when removing the cancer surgically. A few cancer cells left behind can quickly rebuild into a full-blown tumor.

    Enucleation

    • For extreme cases where the entire conjunctiva or the eye itself has become cancerous it may be necessary to remove the entire eye in a procedure called enucleation. This is done under general anesthesia in a hospital setting. Horses can do quite well with just one eye and a little help adjusting to their surroundings.