Ocular neoplasms are less frequent in cats than in dogs; however, the probability of malignancy is higher. 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 nictitating membrane. They generally present as pink, roughened, irregular masses or thickened ulcerations, and the margins are often poorly defined. As with other neoplasms, early diagnosis and referral improve the prognosis.
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 malignant tumors is poor; however, early intervention improves treatment options and prognosis. Advanced imaging and biopsy allow for more accurate diagnoses and treatment options.
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 buphthalmos occur late in the disease. Enucleation is recommended for masses that are fast-growing or produce pupillary abnormalities, iridocorneal angle involvement, or glaucoma, because metastasis is frequent in advanced cases. Cats may also be affected with diffuse iris melanosis, which is a benign process. It can be quite challenging to differentiate diffuse iris melanoma from diffuse iris melanosis. For focal pigmented masses, surgical removal or laser ablation are potential treatment options. For more diffuse lesions, laser ablation may also be a treatment option. Early referral to a specialist is recommended for any pigmented lesion in the iris of a cat.
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 glaucoma, phthisis bulbi, or chronic uveitis. Intraocular cartilage and osteoid production is common. Early enucleation is recommended for this rare neoplasm because this tumor is locally aggressive and invasive.
Feline lymphosarcoma-leukemia complex (FeLLC) is the most common secondary ocular neoplasm in cats. The clinical signs of ocular FeLLC range 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; however, cats with lymphoma and feline leukemia virus Feline Leukemia Virus infection have lower overall survival times.