Page 1197 - Problem-Based Feline Medicine

57 – THE BLIND CAT OR CAT WITH RETINAL DISEASE 1189

Clinical signs trophils, lymphocytes, plasma cells, macrophages and
large, spindle-shaped histiocytes.
Feline infectious peritonitis is an infrequent disease
causing central blindness, and most often occurs in Cases usually show a large increase in IgG due to
young cats that were in multi-cat households or the chronic nature of the disease, seen as increased
obtained from breeders within the previous 18 plasma total protein and globulin concentration.
months. There is a polyclonal increase in gammaglobulins caused
by virus antigen, and cell destruction from the intense
Cats with central blindness have the dry form of FIP,
inflammation associated with the infection.
and usually have a history of uveitis and the classical
signs of hypopyon and keratic precipitates.
INTRACRANIAL NEOPLASIA
The choroid of the eye is homologous embryologically
with the meninges, so cases with meningitis often also
Classical signs
show chorioretinitis.
● Slowly progressive unilateral or bilateral
Central blindness is associated with normal to slow
vision loss.
pupillary light reflexes for cortical lesions, or aniso-
● Older cats.
coria if the midbrain is involved. Concurrent involve-
● Normal pupillary light reflex or anisocoria.
ment of the eyes may result in abnormal reflexes.
● May show neurological signs.
FIP is usually a protracted disease, often with vague
systemic signs such as inappetence, weight loss, See the main reference on page 881 (The Cat With Aniso-
lethargy and pyrexia. coria or Abnormally Dialated or Constricted Pupils).
Central vestibular and cerebellar signs may be seen. Clinical signs
Affected cats often develop seizures.
Intracranial neoplasia causing blindness usually pres-
Ocular disease may initially respond to corticosteroid
ents as an older cat with a loss of vision, which may
therapy, with the cat then developing CNS signs and
be unilateral or bilateral.
blindness weeks or months later.
● If the lesion affects the optic chiasm, the pupils
will be dilated and non-resposive to light. Mening-
iomas and pituitary tumors have been reported in this
Diagnosis area.
There is no definitive diagnosis for FIP. Mid-brain masses may cause anisocoria, but vision
defects will not be as apparent. Meningioma has been
Diagnosis is initially based on the suspicious clinical
reported in this area.
signs of a young cat with uveitis, showing hypopyon
and keratic precipitates, followed up to months later Meningiomas in the region of the visual cortex may
with neurological signs. cause blindness. The pupil should have a normal to
slow response to light.
Serology is usually regarded as being of dubious bene-
fit in the diagnosis, as the FIP organism cross-reacts Diagnosis
with enteric forms of coronavirus.
The clinical presentation of vision loss in an older cat
Diagnosis can only be confirmed on characteristic
with a normal fundus and abnormal PLRs increases the
histopathology of affected tissues on biopsy or necropsy.
index of suspicion for an intracranial mass.
The typical change is described as a pyogranulomatous
vasculitis. Necrosis and a fibrinoid response are seen in CT scan and MRI are useful tools to diagnose and
some cases. The ocular cellular response includes neu- localize the lesion.