The different tissues of the eye and associated structures can develop primary tumors or can be the site of spreading tumor cells. Tumors of the eye are less frequent in cats than in dogs, but those that occur are more likely to be cancerous (malignant).
Eyelid and conjunctival tumors are the most frequent primary eye tumors. These tumors are usually malignant and more difficult to treat in cats than in dogs. Squamous cell carcinomas, which are more common in white cats with noncolored eyelid edges, can involve the eyelids, conjunctivae, and the third eyelid. These tumors are pink, roughened, irregular masses or thickened slow-healing sores. Other less frequent tumors include adenocarcinomas, fibrosarcomas, neurofibrosarcomas, and basal cell carcinomas. Treatment varies with the tumor type, location, and size and includes surgical removal, radiation therapy, and freezing (cryotherapy). The outlook for these tumors is poor, and affected cats typically only survive for 1 to 2 months.
The most common primary tumor within the eyes of cats is widespread melanoma of the iris. In these cases, the iris becomes progressively pigmented (dark brown or black) and develops an expanding irregular surface. Abnormalities in the pupil, glaucoma (high pressure within the eye), and an enlarged eye occur late in the disease. Removal of the eyeball is recommended when these masses are fast-growing, as they may spread to other parts of the body.
Post-traumatic sarcoma within the eye occurs in older cats with a history of longterm inflammation of the uvea (chronic uveitis), previous damage within the eye, or a history of receiving injections of certain medications into the eyeball. Signs include glaucoma (high pressure within the eye), wasting and shrinkage of the eyeball, or longterm inflammation of the uvea. Early removal of the eyeball is usually recommended in these cases.
Feline lymphosarcoma-leukemia complex is a common tumor of the eye. Cats with feline lymphosarcoma-leukemia complex of the eye may have signs affecting one or both eyes, such as inflammation and swelling of the cornea or uvea, excessive formation or rupture of blood vessels in the eye, retinal detachment, abnormal size or shape of the pupil, and lack of pupil dilation. Slow healing sores may also occur. Cats may also have signs of severe, body-wide illness. Tumors can be found in the orbit, eyeball, conjunctivae, and eyelids. Treatment for cats with eye lymphoma has not been well studied, but cats with lymphoma and feline leukemia virus infection have lower overall survival times.
Also see professional content regarding neoplasia in cats.