Page 1343 - Problem-Based Feline Medicine

66 – THE CAT WITH AN ABNORMAL THIRD EYELID 1335

Treatment Differential diagnosis

Surgical excision with good margins is required to Squamous cell carcinoma usually causes more dis-
ensure complete removal. The lesions can sometimes figurement of the third eyelid due to proliferation and
invade deep into the extra-ocular tissues by the time the ulceration.
lesion is recognized.
Other neoplasms such as hemangioma have a charac-
Cryosurgery using liquid nitrogen or nitrous oxide teristic appearance.
with double freeze thaws and slow controlled thawing
Chronic Mycoplasma and Chlamydophila felis in-
can be effective for small tumors less than 0.5 cm diam-
fection may appear similar in some cats, but can be
eter. Maximal destruction of tumor cells occurs when
differentiated on cytological examination of Wright–
temperatures of between −20˚C to −40˚C are achieved
Giemsa-stained slides, immunofluorescent antibody
at the center of the tumor.
and PCR.
b-irradiation with strontium 90 can be effective if
available.
Treatment
Oral corticosteroids: Prednisolone 5 mg orally q
EOSINOPHILIC KERATOCONJUNCTIVITIS**
12–24 h, with dose reducing as effect is achieved.
Classical signs Oral progestagens at a low dose (e.g. megestrol acetate
5 mg twice weekly) should be used only in cases refrac-
● Pink to whitish plaque-like thickening of
tory to oral prednisolone. Beware of possible side
the third eyelid.
effects such as insulin resistance, diabetes and obesity.
● ± Similar lesions on the cornea.
Topical corticosteroids are usually contraindicated
because of an underlying association with ocular her-
Clinical signs pesvirus infection. These drugs may potentiate the her-
pesvirus infection by local immunosuppression.
Appears as pink to whitish plaque-like thickening of
the third eyelid. Similar lesions may appear on the Treat the underlying cause if identified, e.g. treat the
cornea in some cats. ocular herpesvirus infection.

The pathogenesis is unknown, but is postulated to
involve insect bite hypersensitivity or herpesvirus infec-
tion in some cats. Generally there is not a strong asso- SYMPATHETIC NEUROPATHY OF THE
ciation with the presence of other feline eosinophilic THIRD EYELID (HORNER’S SYNDROME)**
disease.
Classical signs
Diagnosis ● Usually unilateral.
● Non-painful prominence of the third eyelid.
Tentative diagnosis is based on the presence of typi- ● Miosis of the ipsilateral pupil.
cal lesions on the third eyelid and cornea. ● Upper lid ptosis.
● Enophthalmos.
Cytological examination of deep scrapings of the lesion
or histopathology of a biopsy specimen demonstrate an
infiltrate of plasma cells and lymphocytes with vari- Pathogenesis
able numbers of eosinophils. Eosinophils may not
Protrusion of the third eyelid occurs where there is dis-
always be the most numerous cell type.
ruption of the sympathetic neural pathways innervating
Tests for herpesvirus infection, e.g. in situ PCR and (see the smooth muscle of the third eyelid (Horner’s syn-
The Cat With Ocular Discharge or Changed Conjunctival drome). Disruption may occur anywhere along the
Appearance, page 1213, for more details). pathway including in the thalamus, cervical spinal cord