Page 1332 - Problem-Based Feline Medicine

1324 PART 15 CAT WITH EYE PROBLEMS

conjunctiva is dissected from the upper defect and There is poor performance of the blink response in tests
sutured to the edge of the transposition flap. Cryosurgery for palpebral or corneal blink.
of hairs near the new conjunctiva–skin margin may be
needed later to correct the remaining upper lid trichiasis.
Diagnosis
More recently a new technique has been described
Diagnosis is usually based on the observation of clini-
involving injection of subdermal collagen into the
cal signs in association with other manifestations of
colobomatous region, and use of a modified Stades tech-
either:
nique to create a hairless scar in the region of the recon-
● Sympathetic dysfunction – miosis, prominent
structed margin. This technique overcomes the traditional
nictitating membrane, enophthalmos.
problem of trichiasis and continuing irritation of the
● CN III dysfunction: internal ophthalmoplegia
cornea by eyelid hairs in the reconstructed region.
occurs due to effects on parasympathetic fibers to
the pupillary constrictor. Dysfunction will result in
UPPER LID PTOSIS* a dilated pupil non-responsive to direct or indi-
rect light, but the opposite eye will show a normal
Classical signs indirect response to light in the affected eye.
External ophthalmoplegia can result in lateral stra-
● Upper lid droops over the globe and ocular
bismus or inability to elevate the eyeball during out-
fissure appears smaller.
ward turning, along with the upper lid ptosis.
● Poor performance of blink response in
tests for palpebral or corneal blink. Use of topical 10% epinephrine will help to differ-
entiate between oculomotor and sympathetic ptosis.
See main reference on page 1335 for details (The Cat Oculomotor ptosis would not be expected to be
With an Abnormal Third Eyelid: sympathetic neuropa- reversed by application of this drug whereas sympa-
thy of the third eyelid). thetic ptosis will disappear transiently.

Pathogenesis Treatment
Sympathetic neuropathy causing denervation of Identify and correct (if possible) the problem causing
Müller’s muscle results in upper lid ptosis. Sympathetic the neuropathy.
neuropathies can be associated with pathology involv-
ing pre- or post-ganglionic fibers.
BACTERIAL BLEPHARITIS, MEIBOMITIS,
● Pre-ganglionic fibers can be damaged at a number
CHALAZION OR HORDOLEUM*
of locations including the descending sympathetic
fibers in the spinal cord (rare), thoracic spinal cord
Classical signs
segments or nerve roots of T1–T3 (nerve root avul-
sion, brachial plexus injuries or anterior media- ● Eyelid swelling, erythema and ulceration.
stinal disease) or the ascending fibers in the ● Mucoid to mucopurulent ocular discharge.
cervical region (e.g. abscess or cellulitis). ● ± Chronic meibomian gland swelling with
● Post-ganglionic fibers are most commonly dam- caseous material or acute abscessation.
aged by middle ear disease.

Cranial nerve III (oculomotor nerve) dysfunction Pathogenesis
affecting the superior palpebral levator.
Bacterial infection is mostly by pathogenic staphylo-
cocci. The most common region of the eyelid involved
Clinical signs is the meibomian gland.
The upper lid does not elevate properly compared to the Pyodermas involving the sebaceous glands of the skin
opposite side, and the upper lid droops over the globe. and associated staphylococcal hypersensitivity are also
The ocular fissure appears smaller than the other eye. seen.