Page 1268 - Problem-Based Feline Medicine

1260 PART 15 CAT WITH EYE PROBLEMS

Clinical signs used infrequently and vary in their sensitivity. PCR is
the most useful of these.
Herpesvirus is one of the most common causes of
● Cytological examination of corneal/conjunctival
acute and chronic corneal disease in older cats.
smears stained with immunoperoxidase may demon-
Acute primary infection with herpesvirus may result strate intranuclear inclusions in epithelial cells in
in the following signs: some acute primary infections, but is not very
● Conjunctival hyperemia and serous ocular reliable.
discharge that becomes purulent by days 5–7 of ● Immunofluorescence using direct or indirect fluo-
infection. rescent antibody techniques on corneal/conjunctival
● Mild to moderate chemosis and blepharospasm. smears or tissue sections may demonstrate the virus,
● Non-specific upper respiratory signs such as but has poor sensitivity.
sneezing and serous nasal discharge. ● Virus isolation is the gold standard for detection,
● Fine-branching (microdendritic) corneal lesions but is not often used because of logistical difficul-
may be seen, especially if the cornea is stained with ties in getting rapid results. It depends on demon-
rose bengal. They result from the direct cytopathic stration of cytopathic effects of the virus in cell
effect of the virus, and are finger-like projections of culture.
epithelium. ● Serological techniques are not very useful because
antibody titers tend to be of low magnitude after
Symblepharon formation with adhesion of conjunctiva
primary infection sometimes reaching only 1:64 at
to conjunctiva and conjunctiva to cornea may follow
60 days after infection. High titers are rarely seen
severe inflammation especially in young kittens.
after recrudescent infection.
Recrudescent infections may show any of the follow- ● Polymerase chain reaction (PCR) testing depends
ing signs: on DNA amplification of an amino acid sequence of
● Dendritic ulcers. the thymidine kinase gene, and is perhaps the most
● Corneal sequestrum. sensitive test available. Theoretically the test could
● Superficial indolent epithelial ulcers. pick up one strand of viral DNA. High sensitivity in
● Serous ocular discharge. nested PCR tests may reduce specificity by the
● Stromal edema and scarring. detection of non-viral DNA contaminants.
FHV-1 keratitis is primarily a disease of older cats.
Frequently unilateral but may be bilateral. CORNEAL SEQUESTRUM (FELINE
KERATITIS NIGRUM)**
A large shallow ulcer with an irregular shape that
appears to look like a continent or land mass (geo-
Classical signs
graphic ulcer) may be evident, and is often associated
with superficial vascularization. It is the result of an ● Area of pigmented cornea varying from
immune response to viral antigen. There may be edema a very light coffee-colored stain to an
and in chronic cases scarring with calcific degeneration intense thick black plaque.
(calcium deposition in the anterior stroma). ● +/- Blepharospasm and photophobia.
● Predominantly in brachycephalic breeds
Typically there is a history of acute episodes followed
such as Persians and Himalayans.
by quiescent periods, but close examination will reveal
● Usually unilateral.
a slightly cloudy, scarred cornea.
See the main reference on page 1234 (The Cat With
Diagnosis
Abnormalities Confined to the Cornea).
A tentative diagnosis is usually based on the clinical
signs. Clinical signs
A definitive diagnosis requires specific techniques, The classic presentation is an area of pigmented
which are available from some la oratories. These are cornea. The degree of pigmentation varies from a very