Page 1280 - Problem-Based Feline Medicine

1272 PART 15 CAT WITH EYE PROBLEMS

Clinical signs The most common cause of lens injury in cats is from
cat fights when a cat claw penetrates the globe and
The center of the lens becomes slightly cloudy, but
tears the anterior lens capsule. This may be obvious
the cat will be able to see quite well until the changes
when the tear is visible through the pupil, but some
are advanced and become a cataract.
injuries occur under the iris root in the equator of the
Nuclear sclerosis is seen from 10 years of age and lens and are not possible to visualize.
cataracts typically occur in cats 12–20 years of age.
Other causes of injury are blunt trauma, which is fre-
On ophthalmoscopic examination, the fundus will be quently associated with motor vehicle accidents. With
clearly visible until a true cataract forms. blunt trauma, the sudden compression of the eye fol-
lowed by rapid decompression causes rupture of the
lens capsule.
Diagnosis
Once the nutrition of the lens fibers is disturbed, the
Diagnosis of nuclear sclerosis is based on clinical
cells will start to die and become opaque, resulting in
signs of a slightly cloudy lens in an older cat, with
typical cloudy lens and cataract formation.
vision intact. The fundus can be clearly seen with an
ophthalmoscope. An injured lens in a cat can lead to sarcoma formation
due to metaplasia of the lens epithelial cells. See pages
Diagnosis of senile cataract is based on clinical signs
1276 (Feline intra-ocular sarcoma).
of a cloudy lens in an older cat, with no history or signs
of preceding ocular trauma or inflammation.
Clinical signs
Treatment
Typically, there is a history or signs of eye trauma,
There is no definitive treatment for this aging change.
usually a cat-fight claw injury or blunt trauma. The
If a cataract develops and the cat is healthy, cataract cornea may have a scar from an old wound.
surgery can be performed. Because senile cataract
Lens may be partially or completely cloudy because of
occurs in aged cats, it is important to check renal func-
an immature or mature cataract.
tion and blood pressure before proceeding with surgery.
In anterior capsule tears, lens material can be seen in
the anterior chamber as a cloudy flocculent material.
CATARACT SECONDARY TO LENS There is intense inflammation associated with leakage
TRAUMA*
of lens material, and it may be difficult to see through
a very cloudy cornea.
Classical signs
Tears in the equatorial region of the lens may often be
● History of previous eye injury, frequently
sealed by the ciliary body and iris root, and only
caused by a cat claw.
develop a local cataract. Generally, an injury to the
● Cornea has scar from old wound.
lens fibers will lead to a mature cataract.
● ± Anterior or posterior synechia (iris
adhesions to cornea or lens). Where the eye has hyphema (red eye), the lens will not
● Lens may be partially or completely cloudy. be able to be seen ophthalmoscopically.
● ± Chronic inflammation (uveitis) caused by
Often the tear in the lens capsule has iris pigment
lens protein outside the capsule.
adhered to it, visible as a black area. Anterior or
posterior synechia (iris adhesions to cornea or lens)
Pathogenesis may be evident.

Any injury to the lens fibers will disrupt the normal Be aware that cats with chronic inflammation after
lens metabolism, and cause death of lens fibers leading trauma often have a ruptured lens causing chronic
to cataract formation. lens-induced uveitis.