Page 1318 - Problem-Based Feline Medicine

1310 PART 15 CAT WITH EYE PROBLEMS

Bilateral abnormalities are more likely to be associ- Pathogenesis
ated with systemic disease, whereas unilateral prob-
Cellulitis is induced by bacterial infection of the orbital
lems are more likely to reflect local phenomena, for
soft tissue. Bacteria are introduced into the tissue by
example, lymphoma involving the orbit will usually
several routes:
cause bilateral exophthalmos.
● Blood-borne via vessels within the orbit.
The final decision as to whether there is a change ● Traumatic inoculation through the oral mucous
in size or a change in position might lie with a membranes caudal to the upper molar tooth from
consideration of the associated ocular signs, for sharp foreign bodies such as a bone, or by iatro-
example: genic introduction during orbital exploration.
● If buphthalmos rather than an exophthalmos is ● Spread of infection associated with periodontal dis-
suspected, then look for associated signs which one ease of caudal maxillary teeth.
might expect to see with glaucoma and buphthal- ● Spread from an area of osteomyelitis involving
mos, that is, dilated to mid-dilated non-responsive bone around the orbit.
pupil, deep episcleral vessel injection, high intra-
Iatrogenic non-septic cellulitis can occur by trauma of
ocular pressure measured with a tonometer, vision
orbital tissues during surgical exploration behind the
loss, and fundoscopic suggestion of retinal degen-
upper M1 tooth with serrated cutting devices such as
eration.
hemostats.
● If exophthalmos is suspected rather than buph-
thalmos, then look for pain on opening the mouth,
poor retropulsion, signs of ventral orbital swelling Clinical signs
behind the last upper molar teeth, and swelling of
Typically there is a very acute onset of signs over a few
peri-ocular tissue.
days.
● If enophthalmos is suspected rather than pthisis,
look for a prominent but not swollen third eyelid. Pain is evident, especially on opening the mouth.
● If reduced size is suspected, look for signs of chronic
A normal-sized globe is pushed cranially (exophthalmos).
intra-ocular inflammation, low intra-ocular pres-
sure on tonometry and/or possible signs of globe Prominent nictitating membrane.
rupture and aqueous leakage.
Fever is variably present.

Peri-orbital swelling causes swelling of conjunctival
DISEASES CAUSING INCREASED tissue around the globe (chemosis), and conjunctiva
GLOBE SIZE OR PROMINENCE
become exposed and dry.
Occasionally bulging of oral mucosa caudal to upper
BACTERIAL ORBITAL CELLULITIS*** M1 may be evident.
OR NON-SEPTIC CELLULITIS OR
HEMORRHAGE If the cellulitis, hemorrhage and/or edema are associ-
ated with blind surgical orbital exploration, signs of
Classical signs exophthalmos and peri-ocular swelling become more
pronounced following the procedure.
● Acute in onset over a few days.
● Exophthalmos.
● Pain on opening mouth. Diagnosis
● Prominent nictitating membrane.
History is usually of a rapid onset of signs over a few days.
● ± Fever.
● Occasionally bulging of oral mucosa caudal Classical signs are exophthalmos, chemosis, third eye-
to upper M1 tooth. lid prominence, and peri-ocular swelling, which are
● Chemosis. usually associated with pain on palpation, retropulsion
or opening of the mouth.