Page 1186 - Problem-Based Feline Medicine

1178 PART 15 CAT WITH EYE PROBLEMS

The retina may not be visible due to the hyphema. If
GLAUCOMA CAUSING RETINAL
there is hemorrhage in the inter-retinal space between
DEGENERATION
the retinal pigment epithelium and the rods and cones,
the retina will bulge forward with a red appearance.
Classical signs
Loss of vision may be caused by trauma to the optic
● Buphthalmos (an enlarged globe).
nerve. It is not possible to visualize this part of the
● Increased intra-ocular pressure.
nerve, but hemorrhages may be present on the optic
● Dilated pupil, poorly or non-responsive to
disc.
light.
Beware of secondary glaucoma. Initially, traumatized ● Hyper-reflective tapetum.
eyes are very soft. Glaucoma may follow acutely from ● Luxated lens or cataract.
obstruction of the iridocorneal angle by hemorrhage,
lens luxation or rupture, and inflammation. Cases with See the main reference on page 1232 (The Cat With
chronic retinal detachment may form vascular mem- Ocular Discharge or Changed Conjunctival Appearance).
branes, which obstruct the drainage angle.
Clinical signs
Diagnosis
Cats blinded from glaucoma will have an enlarged
Diagnosis is based on clinical signs of a cat presented globe (buphthalmos), and the condition will be
with an acutely painful, red eye. Carefully examine chronic.
the eye to determine the extent of the injury. If the
Deep episcleral vessel injection is seen in eyes with a
fundus is visible ophthalmoscopically, the retina will
high intra-ocular pressure (above 30 mmHg). Compared
be able to be examined, and areas with hemorrhage and
to superficial episcleral vessels, the deep vessels are
detachment will be visible.
usually straighter and larger, do not move when the
Ocular ultrasound using a 10-megahertz stand-off overlying bulbar conjunctiva is moved, and do not
probe, is a very useful diagnostic tool when the fundus blanch with the topical application of 1:1000 epineph-
cannot be visualized because of severe hyphema. rine.
Retinal detachment will show as a bulging hypoechoic
The pupil is dilated or semidilated, with either absent
line. Pay particular attention to the shape of the globe,
or poor pupillary light reflex.
as severely traumatized eyes may also have a rupture of
the sclera posteriorly, and this will have a very poor There may be signs of chronic anterior uveitis, espe-
prognosis. Try to visualize the muscle cone and optic cially abnormalities in the appearance of the iris surface
nerve for swelling. for example:
● Pinkish discoloration associated with fibrovascu-
Use tonometry to monitor intra-ocular pressure.
lar membrane formation.
● Grayish nodules on the iris surface.
Treatment There may be signs of lens instability including:
● An aphakic crescent (crescent shape produced by
Treatment is usually conservative, and includes
the clear space between the edge of the displaced
antibiotics and anti-inflammatory drugs.
lens and the adjacent pupillary margin).
● Systemic broad-spectrum antibiotic cover to pre-
● Anterior or posterior luxation (dislocation).
vent hematogenous infection.
● Iridodonesis (wobbling of the iris).
● Systemic anti-inflammatory drugs to reduce
inflammation and prevent secondary complications There may be signs of intra-ocular neoplasia.
in the eye, such as prednisolone 1 mg/kg bid or a
Prolonged increased intra-ocular pressure results in
NSAID like ketaprofen, cartrophen or metacam.
collapse of the cribriform plate. This causes obstruc-
In cases with exophthalmos, do a temporary tarsor- tion to retinal vascular flow at the level of the optic
rhaphy to protect the cornea. disc, and obstruction to the axoplasmic flow in the optic