Page 1272 - Problem-Based Feline Medicine

1264 PART 15 CAT WITH EYE PROBLEMS

Corneal healing is achieved by epithelial regenera-
MYCOBACTERIAL KERATITIS
tion and stromal repair.
(FLORIDA SPOTS)
Epithelial regeneration occurs by:
● Sliding of cells to cover the surface. Classical signs
● Mitosis to reconstruct the layers.
● An asymptomatic keratitis recognized in
Stromal repair occurs via avascular and vascular the southeastern USA.
healing. ● The cornea has focal gray-white opacities
● A vascular healing occurs in small uncomplicated in the anterior stroma, varying in diameter
wounds and involves: from 1–8 mm in size.
– Infiltration of neutrophils from the tear film and ● The lesions usually affect both eyes.
limbal blood vessels.
– Macrophages invade, and digest the cellular See the main reference on page 1251 (The Cat With
debris. Abnormalities Confined to the Cornea).
– Keratocytes transform to fibrocytes that migrate
into the damaged area. Clinical signs
– Collagen fibrils are laid down in an irregular pat-
One, or more commonly, both corneas have focal
tern that disrupts the corneal transparency.
white to gray opacities in the anterior stroma.
● Vascular healing occurs when there is extensive
stromal loss. The condition is asymptomatic, as cats show no signs
– Cellular infiltration is more extensive. of ocular pain or irritation, and there is no associated
– Blood vessels invade from the limbus. inflammation in the cornea.
– Granulation tissue forms and this heals in a
The condition has only been described in the USA.
dense scar.
Diagnosis
Clinical signs A tentative diagnosis is based on clinical signs –
multiple focal opacities in the anterior stroma of the
Scars present as cloudy areas on the cornea.
cornea, not associated with irritation or inflammation.
Superficial scarring of the cornea is seen as a faint
cloudiness of the superficial stroma. Dense opacity is Rhinosporidium was initially diagnosed from histo-
seen with deep scars that involve the deep layers of the logical samples. However, ultrastructural examination
cornea. of affected cornea showed vacuoles with amorphous
material and rod-like organisms characteristic of
Scars vary considerably in position, size, shape and
mycobacteria that stain positively with Ziehl–Neelsen
density depending on the depth and area of corneal
carbolfuchsin stain.
stroma that has been damaged.
Usually there is no inflammation in the affected eye. CORNEAL (STROMAL) DYSTROPHY OF
MANX CATS
Vision is always affected by corneal scarring.
Classical signs
Diagnosis ● Young Manx cats.
● Begins with stromal edema that
A diagnosis is based on clinical findings and history.
progresses to a cornea filled with large
Typically the cornea has cloudy areas of varying den-
bullae.
sity, there is no positive staining with fluorescein, and
● Eventually causes blindness.
the eye has no sign of inflammation, pain or discharge.
Usually, there is a history of previous severe inflam- See the main reference on page 1252 (The Cat With
mation or trauma, with healing of the cornea. Abnormalities Confined to the Cornea).