Page 1255 - Problem-Based Feline Medicine

60 – THE CAT WITH ABNORMALITIES CONFINED TO THE CORNEA 1247

bacteria especially Pseudomonas spp., which produce is very elastic in cats and can bulge forward quite
proteolytic enzymes. noticeably.
Where the cornea is soft and gelatinous, a swab should
Clinical signs
be taken from the lesion and sent to the laboratory for
Eyes with ulceration are invariably very painful. Cats culture and sensitivity.
show serous ocular discharge, blepharospasm, photo-
Perforating injuries are very painful, and show changes
phobia and ocular guarding in severe injuries.
in the anterior chamber such as hyphema and protein
Ulcers stain positive with fluorescein dye. A very leakage with fibrin, whereas non-perforating ulcers
deep ulcer that has formed a Descemetocele may not such as descemetocele rarely show changes in the ante-
show any staining because Descemet’s membrane will rior chamber.
not hold dye.
Examination of the cornea with magnification will Differential diagnosis
show a deficit in the corneal surface due to loss of
Herpetic keratitis.
epithelium and stroma.
● Usually appears as a superficial ulcer with an irreg-
Corneal edema will be present in cases that have loss ular appearance.
of epithelium, because fluid will be absorbed by the ● PCR tests may be helpful to differentiate from
stromal matrix. This will show as a cloudy cornea. chronic superficial ulceration.
Edema may be focal, around the ulcer or diffuse when
Eosinophilic keratitis.
large ulcers are present.
● This is a proliferative lesion, but the epithelium
A Desemetocele usually looks like a thin, bulging may be eroded with a positive fluorescein stain.
membrane in an area where there is a very deep ulcer. ● Cytology should show the presence of eosinophils.
It may have a black appearance caused by a reflection
Iris prolapse (differential for descemetocele).
from the pupil behind. It is usually a more chronic con-
● An acute, very painful eye with cloudy cornea and
dition in the cat where there has been an ulcer for some
usually hemorrhage in the anterior chamber. The eye
time.
will be soft and the anterior chamber shallow. The
Cats with chronic ulcers often do not show much prolapsed iris tissue may be black or brownish in
inflammatory reaction in the cornea. It is common to color depending on the degree of pigmentation in the
see chronic ulceration in cats with no sign of neovas- iris. There may be a fibrin clot present over the iris,
cularization. plugging the wound. The wound is usually linear in
shape rather than oval to round as seen in ulcers.
Ulcers that develop into a melting cornea are devastat-
ing conditions that appear with a rapidly developing
cloudy edematous cornea that has a gelatinous soft
Treatment
appearance. The eye is extremely painful and the
threat of rupture is very high. They are often infected As a general rule, eliminate the cause of the ulcer and
with Pseudomonas spp. provide protection for the cornea using lubrication,
appropriate antibiotics where necessary and surgical
techniques to close and protect the eye.
Diagnosis
Superficial epithelial erosions heal rapidly with mini-
There may be a history of trauma or a cat fight. The
mal treatment. The use of antibiotics is not encouraged
diagnosis is made on clinical examination by finding
as they are rarely infected. Support with artificial tear
a painful eye showing a stromal deficit.
solutions will make the eye more comfortable.
The ulcer will stain with fluorescein except in the case
Corneas with deep ulcers that have stromal loss need
of a Descemetocele.
to be protected with surgical techniques such as third
If the center of the ulcer is dark, and the area bulges, eyelid flaps or temporary tarsorrhaphies (see references
there may be a Descemetocele. Descemet’s membrane for texts that show details of these surgical techniques).