Page 1320 - Problem-Based Feline Medicine

1312 PART 15 CAT WITH EYE PROBLEMS

Blindness or abnormality of the pupillary light reflex Prognosis
occurs if the optic nerve or CN III is affected by the
Prognosis is poor for invasive orbital fibrosarcoma or
neoplastic process but this is uncommon.
squamous cell carcinoma.
Lymphosarcoma usually results in bilateral globe
Orbital lymphosarcoma has a guarded prognosis.
prominence and peri-ocular tissue swelling. Sometimes
it is associated with anterior uveitis evidenced by
BUPHTHALMOS ASSOCIATED WITH
intra-ocular fibrin, hemorrhage and/or iris masses. It
GLAUCOMA**
may occur in conjunction with other signs of multicen-
tric lymphoma.
Classical signs
Squamous cell carcinoma more often causes uni-
● Enlarged globe.
lateral globe prominence, and there is evidence of
● Deep episceral vessel injection.
co-existent neoplasia involving oral or nasal mucous
● Associated with signs of chronic anterior
membranes or pre-existent eyelid or conjunctival neo-
uveitis, uveal neoplasia and secondary
plasia in a cat with non-pigmented eyelid margins.
glaucoma.
Fibrosarcoma or osteosarcoma typically produce a
unilateral, slow-onset increase in globe prominence or
Pathogenesis
globe displacement and peri-ocular swelling.
Buphthalmos occurs from stretching of the fibrous
Diagnosis outer tunic of the eye associated with elevated intra-
ocular pressure. In the cat, most cases of glaucoma are
Orbital neoplasia should be suspected in any case of
secondary to chronic anterior uveitis or iris neoplasia.
non-painful or mildly painful exophthalmos with a
slow onset and progression of signs. Primary glaucoma has been described in Burmese
cats in Australia, which appears to be familial. In this
Ultrasound is a particularly useful imaging technique.
condition there appears to be a genetically determined
Plain radiographs of the maxilla, frontal bone and
narrowing of the irido-corneal angle resulting eventu-
zygomatic arch may be useful, and CT or MRI may be
ally in reduced aqueous outflow and increased intra-
needed in special circumstances.
ocular pressure.
Differential diagnosis
Clinical signs
Orbital cellulitis usually causes a more painful exoph-
The globe is more prominent because it is enlarged
thalmos of more rapid onset.
(buphthalmos).
Deep episcleral vessels are injected secondary to
Treatment
increased intra-ocular pressure. Deep vessels are usually
Chemotherapy is used for treatment of lymphosar- straighter and larger, do not move when the overlying
coma. See main reference on page 432 for details (The bulbar conjunctiva is moved, and do not blanch with the
Cat With Enlarged Lymph Nodes). topical application of 1:1000 epinephrine.
Squamous cell carcinoma and fibrosarcoma can be The pupil is dilated or semi-dilated, and the pupillary
treated by surgery with or without irradiation. light response is either absent or poor.
● Radical surgical excision is required, and aim to re-
Signs of chronic anterior uveitis are often present,
move 1–2 planes of normal tissue with the affected
especially abnormalities in the appearance of the iris sur-
tissue.
face. The iris may have a pinkish discoloration associ-
● Megavoltage or orthovoltage irradiation of the orbit
ated with fibrovascular membranes or grayish nodules.
can be used to attempt prevention of regrowth of
invasive neoplasms where surgical excision does not The anterior chamber may appear to be very shallow
achieve clean margins. in aqueous misdirection glaucoma, which is a poorly