Page 1245 - Problem-Based Feline Medicine

60 – THE CAT WITH ABNORMALITIES CONFINED TO THE CORNEA 1237

vascularization. Superficial blood vessels grow in a
DISEASES CAUSING ABNORMALITIES
branching pattern and may bring melanin cells with
CONFINED TO THE CORNEA
them, causing pigmentation and loss of transparency.
Acute inflammation within the eye (uveitis) will
FELINE HERPESVIRUS-1 (FHV-1)
cause an intense, deep stromal vascular infiltration around
KERATITIS***
the periphery (limbus) known as a “brush border”.
Corneal edema and keratic precipitates are seen in eyes
Classical signs
that have uveitis. The epithelium is usually intact, but
the endothelium is disrupted. ● Kittens may have swollen red eyes with a
serous discharge. In very severe cases this
Corneal pigmentation develops secondary to corneal
may be followed by a cloudy appearance of
vascularization as melanin cells from the limbal
the cornea. The cornea is covered by a
melanocytes are dragged into the stroma with the blood
conjunctival membrane and has a dull gray
vessels. This is not as common a reaction in the cat
appearance, sometimes with superficial
compared to other species.
vascularization.
Corneal edema can be seen in cases with glaucoma, ● Young cats may present with signs of ocular
because the increased intra-ocular pressure disrupts the pain (blepharospasm and photophobia) and
endothelium, allowing aqueous to enter the stroma. The serous discharge. Microscopic examination
epithelium is usually intact. of the cornea may show dendritic lesions
seen as a faint branching within the
epithelium. They may stain positive with
rose bengal stain.
WHERE? ● Older cats develop chronic painful eyes that
may have a slightly cloudy cornea with
Corneal epithelium stroma (keratocytes and matrix)
some faint blood vessels present. This is
and endothelium.
caused by shallow irregular ulceration
(geographic ulcer) often with faint
superficial vascularization.
WHAT? ● Older cats frequently have a history of
acute episodes followed by quiescent
Most superficial corneal epithelial problems are caused periods, but close examination will reveal
by trauma or infections, specifically herpesvirus-1. a slightly cloudy, scarred cornea.
● The condition is frequently unilateral but
Corneal stromal problems are caused by trauma, her-
may be bilateral.
pesvirus or degeneration associated with corneal
sequestrum. Cloudiness of the cornea is caused by
edema or scarring. See main reference on page 1212 for details (The Cat
With Ocular Discharge or Changed Conjunctival Appea-
Proliferative corneal lesions are usually caused by an rance) and The Cat With Acute Sneezing or Nasal
immune-mediated reaction known as eosinophilic Discharge (page 7).
keratoconjunctivitis.
Corneal endothelial problems are caused by trauma, Pathogenesis
uveitis, glaucoma, and very rarely, endothelial dystrophy.
Herpesvirus infection is one of the most common causes
Non-specific reactions that cause edema and chronic of acute and chronic corneal disease in older cats
keratitis can be seen with glaucoma.
The condition is caused by infection with feline herpes
Congenital diseases of the cornea are rare in cats. virus-1 (FHV-1), a subfamily of Herpesvirinae. FHV-1