Ocular Neoplasia in Cats
Ocular neoplasms are less frequent in cats than in dogs and tend to be more malignant. Approximately 2% of feline patients present with neoplasia, and of these, 2% are affected with ophthalmic tumors. Eyelid and conjunctival tumors are the most frequent primary ophthalmic neoplasms. These neoplasms are usually malignant and more difficult to treat in cats than in dogs. Squamous cell carcinomas, which are more common in white cats with nonpigmented eyelid margins, can involve the eyelids, conjunctivae, and the nictitating membrane; they are pink, roughened, irregular masses or thickened ulcerations. Other less frequent neoplasms include adenocarcinomas, fibrosarcomas, neurofibrosarcomas, and basal cell carcinomas. Treatment varies with the tumor type, location, and size and includes surgical excision, radiation therapy, and cryotherapy. Prognosis for these malignant tumors is poor, with survival of only 1–2 mo.
The most common primary intraocular neoplasm in cats is diffuse iridal melanoma, which presents as progressive hyperpigmentation of the iris with an expanding irregular surface. Pupillary abnormalities, secondary glaucoma due to iridocorneal angle obstruction, and buphthalmia occur late in the disease. Enucleation is recommended for masses that are fast-growing or produce pupillary abnormalities, iridocorneal angle involvement, and/or glaucoma, because metastasis is frequent in advanced cases.
Post-traumatic intraocular sarcoma occurs in older cats with a history of chronic uveitis, previous intraocular damage, or intraocular injections of gentamicin. Clinical signs are either glaucoma, phthisis bulbi, or chronic uveitis. Intraocular cartilage and osteoid production is common. Early enucleation is recommended.
Feline lymphosarcoma-leukemia complex (FeLLC) is the most common secondary ocular neoplasm. Cats with ocular FeLLC have clinical signs ranging from isolated ocular lesions (affecting one or both eyes) to severe systemic illness. Corneal abnormalities may include keratitis, edema, neovascularization, corneal infiltrates, and hemorrhages within the stroma. Ulcerative keratitis may result. Masses can be found in the orbit, globe, conjunctivae, and eyelids. Pupillary abnormalities, including mydriasis, anisocoria, spastic pupil syndrome, "D" or reverse "D" pupil shape, and lack of light-induced pupillary reflexes, may develop months before other clinical signs. Anterior uveitis is the most common clinical finding in FeLLC. Other findings include ocular hypotension, changes in iridal pigmentation and color, keratic precipitates, hyphema, anterior and posterior synechiae, miosis, and aqueous flare. Posterior segment changes include retinal hemorrhages, tortuous dilated vessels, perivascular cuffing, and detachment and degeneration of the retina. Few therapy studies of cats with ophthalmic lymphoma exist, but cats with lymphoma and feline leukemia virus infection have lower overall survival times.