Page 1341 - Problem-Based Feline Medicine

66 – THE CAT WITH AN ABNORMAL THIRD EYELID 1333

Inflammatory disease is occasionally seen, and can be Although herpesvirus, Chlamydophila felis and Myco-
of infectious or non-infectious, immune-mediated or plasma infection may be difficult to distinguish clini-
allergic etiology. cally in some cats, in other cats signs may be suggestive
of the causative agent.
Neoplasia involving the conjunctiva of the third eyelid
● Herpesvirsus typically causes bilateral serous
occurs infrequently.
conjunctivitis in conjunction with other upper res-
piratory signs (sneezing, nasal discharge).
DISEASES CAUSING ABNORMAL
THIRD EYELID APPEARANCE Discharge rapidly becomes mucopurulent and the
cat is depressed, anorexic and febrile. In some cats,
dendritic ulcerative keratitis may occur initially.
INFECTIOUS DISEASE INVOLVING Non-ulcerative stromal keratitis and/or corneal
CONJUNCTIVA OF THE THIRD sequestration may occur several weeks to a few
EYELID*** (FELINE HERPESVIRUS-1**, months after the initial infection, which may have
CHLAMYDOPHILA FELIS** AND been unnoticed. Symblepharon may be seen as a
MYCOPLASMA* INFECTION) sequel in young cats.
● Chlamydial conjunctivitis typically appears as
Classical signs severe hyperemia and chemosis of conjunctival sur-
faces. It is associated with mucopurulent discharge,
● Inflammation and chemosis (swelling)
usually starting in one eye and later progressing to
specifically involving the conjunctiva of the involve the contralateral eye.
third eyelid.
● Discharge varies from serous or mucoid to ● Mycoplasmal conjunctivitis appears as unilateral
or bilateral conjunctivitis, associated with epiphora,
mucopurulent.
papillary hypertrophy of conjunctiva, conjunctival
follicles, chemosis, and occasionally thick white
See main references on feline herpesvirus, chlamydial
pseudomambrane.
and mycoplasmal infection on pages 1212, 1218 for
details (The Cat With Ocular Discharge or Changed
Conjunctival Appearance).
Diagnosis
Clinical signs
A tentative diagnosis is often made on the signs of
Typically there is inflammation and chemosis inflammation, chemosis and discharge associated with
(swelling) specifically involving the conjunctiva of the upper respiratory tract signs.
third eyelid. Usually the associated bulbar and palpe-
A definitive diagnosis requires identification of the
bral conjunctivae are also affected.
organism on conjunctival cytologic preparations stained
There may be signs of upper respiratory tract disease with Wright–Giemsa, e.g.
in the early stages, although all these organisms may also ● Membrane-bound basophilic intracytoplasmic
cause conjunctivitis unassociated with typical upper res- inclusions indicate chlamydial infection.
piratory tract signs. Conjunctivitis alone may occur in cats ● Small basophilic-staining pleomorphic organisms
with previous exposure that have developed immunity, or closely associated with the cell membrane surface
it may represent recrudescence of signs in carrier cats. indicate mycoplasmal infection.

Discharge varies from serous or mucoid to mucopu- Specific tests are available for the diagnosis of infec-
rulent. The type of discharge seen is dependent on the tious disease especially in the early stages, e.g.
stage of the infection, for example, FHV-1 herpesvirus ● Herpesvirus: immunofluorescent antibody (IFA),
infections usually cause a serous discharge in the early virus isolation (VI) and polymerase chain reaction
stages, which progresses to a mucopurulent discharge (PCR).
secondary to bacterial infection. ● Chlamydophila felis: IFA and PCR.