Page 1312 - Problem-Based Feline Medicine

1304 PART 15 CAT WITH EYE PROBLEMS

Clinical signs ● Iris collarette to another region of the iris collarette.
The iris collarette is a raised area approximately half
Idiopathic uveitis is characterized by any signs of
way between the iris root and the pupillary margin.
anterior uveitis such as miosis, injected iris surface,
● Iris to anterior capsule.
anterior chamber flare, and fibrin, where extensive lab-
● Iris to posterior corneal surface (most common).
oratory investigations fails to identify a possible
etiology. The strands can be very thin and magnification may be
required to visualize them.
One study showed there may be a significant positive
association of idiopathic anterior uveitis with high Persistent papillary membrane may also appear as dot-
aqueous titers to herpesvirus. like gray to black opacities on the endothelial sur-
face of the cornea or the anterior capsule of the lens,
Diagnosis unassociated with history of previous inflammation
within the eye.
Diagnosis is based on the clinical signs of uveitis with
failure to identify a possible cause.
Diagnosis
PERSISTENT PUPILLARY MEMBRANES Diagnosis is based on the characteristic appearance of
the PPMs on careful ocular examination.
Classical signs
● Strands of iris-like tissue arising from the Differential diagnosis
iris collarette and crossing the pupil space,
The gray opacities formed by PPMs which attach to the
or attaching to the cornea or lens.
corneal endothelium should be differentiated from kera-
● Dot-like gray to black opacities on the
tic precipitates, formed as a result of anterior uveitis.
endothelial surface of the cornea or the
A strand of tissue attaching the opacity to the iris and
anterior capsule of the lens unassociated
the absence of other signs of anterior uveitis is diag-
with history of previous inflammation
nostic of a PPM.
within the eye.
● Rare in cats.
Treatment
Pathogenesis No treatment is indicated for PPMs.
Persistent papillary membrane is an embryonic struc-
ture, and results from failure of the pupillary mem- IRIS COLOBOMA
brane to rarify in late fetal life.
Classical signs
The pupillary membrane is formed from mesoderm,
which, until regression, forms a solid sheet of tissue ● Segmental full-thickness defect of the iris
bridging the pupil space from the iris collarette. In normal with lens visible behind the defect.
adult cats, the collarette appears as a slightly raised region ● Remaining iris is normal.
halfway between the pupil margin and the iris root. ● May also cause an abnormal pupil shape.
● Rare in cats.
The condition is seen rarely in cats compared to the fre-
quency with which it is seen in dogs, and rarely seems
to affect the pupil light response or pupil shape.
Clinical signs
Clinical signs
The defect is a rare anomaly that may be detected in
Persistent papillary membrane appears as fibrous a young cat, and results in a notch-like or sectorial
strands of iris-like tissue running from the: defect in the iris.