Acquired Disorders

Traumatic Proptosis

Proptosis of the globe is a serious disease in the cat, because to occur, it requires considerable trauma to the orbit and head and is associated with concurrent facial fractures and optic nerve damage. In one series of traumatic proptosis among 18 cats, no eyes regained vision. Sexually intact males were more frequently affected, and being hit by a car was the most frequently established source of trauma. In 16 of the 18 affected cats, facial bone fractures, hyphema, corneal perforation, and ocular desiccation were common. In only two of the 18 cats was replacement of the globe and temporary tarsorrhaphy even attempted.

Orbital Inflammations and Infections

The feline orbit has relatively limited space compared with that of the dog. Hence, space-occupying orbital inflammations and neoplasms will produce exophthalmos, deviation of the globe, and protrusion of the nictitating membrane early in the disease process. Orbital surgeries, including enucleations, are also more difficult to perform because of the limited peribulbar space.

Orbital cellulitis and abscessation caused by bacteria occur infrequently in the cat (Figure 16.42), but are usually amenable to traditional therapy of drainage and antibiotic administration.

In a study of orbital bacterial infections, five of seven cats had positive bacterial isolation, with Pasturella and Bacteroides the most common. Onchocerca lupi was the causative agent of orbital cellulitis in two cats. Fungal agents causing orbital infections include Peni-cillium spp., Pythium insidiosum, and Aspergillus spp.

Figure 16.42. Bacterial orbital cellulitis/abscess in a young Domestic Shorthair. Note the exophthalmia, lagophthalmos with corneal drying, elevated third eyelid, and purulent nasal discharge.

Clinical signs in these animals may include exophthalmos, corneal drying with possible ulceration secondary to lagophthalmos, ocular discharge, oral cavity ulceration, pain upon opening of the mouth, and nasal discharge if the infection involves the nasal cavity or sinuses. In most reports of feline orbital aspergillosis, the cats have been Persians. Surgical therapy alone, including orbital exenteration, has not typically been successful.

Orbital foreign bodies have occasionally been reported in the cat. A 13-year-old cat with a 1-week history of periorbital swelling and exophthalmos had a predominantly eosinophilic inflammatory cell infiltrate in the orbital tissue that was biopsied. The cat was treated with oral prednisolone in a tapering dose over 4 weeks and had no recurrence over a 2-year follow-up. Orbital emphysema associated with frontal sinus penetration has also been reported in a cat. An idiopathic sclerosing orbital disease has been described in seven cats (six Domestic Shorthairs and one Persian) in one case series and in one Domestic Shorthair in a single case report. The features of the condition are similar to those of sclerosing orbital pseudotumor in humans. In affected cats, the onset of the disease is insidious, with progression over weeks to months. Orbital tissues and eyelids become fixed in place by fibrous tissue. In all of the described cats, the condition became bilateral. Exposure keratitis, corneal ulceration, and corneal perforation were prominent features of the disease due to the inability of the eyelids to move. Treatment included oral corticosteroids, oral antibiotics, and radiation therapy in one cat. Additionally, three cats received surgical therapy, including entropion repair and temporary tarsorrhaphy. In all cases, response to treatment was poor.

Orbital Neoplasia

Orbital neoplasia are fairly common in cats. In one series, approximately two-thirds of the neoplasms were epithelial in origin, with SCCs being the most frequent type. Approximately 15 different types of orbital tumors have been reported in the cat, including osteoma of the zygomatic arch, parosteal osteoma, and fibrosarcoma. Depending on the tissue of origin and the invasiveness of an orbital tumor, therapeutic options may include surgery (orbitotomy with tumor resection or exenteration), radiation therapy, and chemotherapy.

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