Page 1254 - Problem-Based Feline Medicine

1246 PART 15 CAT WITH EYE PROBLEMS

Pseudomonas aeruginosa, which can be cultured The prognosis is improved if the cause of the allergic
from the edge of the ulcer with a swab moistened in state can be found and controlled.
sterile saline.
Chronic herpetic keratitis. ULCERATIVE KERATITIS (NOT
● Chronic herpetic keratitis may present with a large ASSOCIATED WITH SPECIFIC CORNEAL
irregular area of corneal scarring and mild super- DISEASE OR CORNEAL PERFORATION)*
ficial corneal vascularization, but the lesion usually
has superficial ulceration and is not proliferative. Classical signs
The cornea rarely shows the same intense vascular-
● Ocular pain with serous discharge,
ization and edema seen in eosinophilic keratitis.
blepharospasm and photophobia.
● There will be a history of poor response to anti-
● Varying degrees of corneal cloudiness.
biotic therapy.
● Very cloudy cornea with a soft gelatinous
● Cytology will not reveal eosinophils.
appearance (melting ulcers or
● PCR tests on conjunctival and corneal tissue may
keratomalacia).
help to differentiate.
● Black area within a cloudy cornea, and
Neoplasia. a thin, bulging membrane at the center
● Squamous cell carcinoma of the cornea has been (Descemetocele).
seen, but it is a very rare condition in cats. The ● Positive staining of the stroma with
lesion is proliferative but there will not be much fluorescein dye, except where a
ocular discharge. Descemetocele is present.
● Cytology or fine-needle biopsy will confirm this
condition.

Pathogenesis
Treatment
Most ulcers that are not associated with a specific
The condition will rapidly respond to systemic corti- corneal disease state are caused by corneal trauma.
costeroids dosed at 1 mg/kg q 12 h PO. Foreign bodies such as grass seeds and thorns, or
blunt trauma from motor vehicle accidents are the
Topical prenisolone acetate 0.5 or 1% drops applied q
most common causes of corneal trauma. Trauma may
8–12 h are excellent providing there is no ulceration of
cause a superficial ulcer, a deep ulcer or penetrating
the cornea.
wound.
If tips of the ears show alopecia, pruritis and crusting
Ulcers may vary from a superficial loss of epithelium
the condition may be caused by biting insects. Such
to a deep stromal defect.
cases have been documented in Queensland, Australia.
These cats should be housed in conditions that are Corneal edema develops when there is loss of epithe-
insect free to prevent reoccurrence. lium, because the stroma absorbs fluid causing the stro-
mal matrix to swell.
Allergic states caused by diet have been implicated.
Dietary exclusion tests may be useful to eliminate this A Descemetocele forms when there is no stromal tis-
as a cause. See “The Cat With Signs of Chronic Small sue present, but Descemet’s membrane is intact. In
Bowel Diarrhea” (page 739). cats, Descemet’s membrane is very elastic and can
bulge considerably within the corneal defect.
Melting ulcers (keratomalacia) develop when the
Prognosis
stromal tissue undergoes some form of autolysis. This
The prognosis is very favorable in cases that respond to may occur from proteolytic enzymes present in dam-
corticosteroids. Corneal scarring may be a sequela after aged epithelial cells, from enzymes produced by neu-
chronic keratitis. trophils and macrophages in the tear film, and from