
Ulcers of the cornea in dogs and cats is a common occurrence, and a
potentially dangerous affliction. Any abrasion to the cornea,
including an bee sting, rub from a paw, a scratch from a claw or thorn or an
invasive infection can abrade the cells on the surface of the dog or
cat cornea. Once the surface cells are disrupted the
smooth surface of the cornea becomes rough, infective organisms can invaded
the spaces between the cells and the area becomes a source of pain and
irritation to the animal. Dogs and cats with corneal ulcers commonly
will have increased tear production, will squint (called blepharospasm) and
rub at their eye. The irritated tissues often become infected.
If infection progresses into the thin cellular layers of the
cornea, the ulcer may deepen and widen and eventually break through the
membrane at the back of the cornea called Descemet's membrane. In
these severe cases, the fluid from the anterior chamber of the eye can
escape and the front of the eye collapses. When this occurs, called a
descemetocele, the iris will often seal the hole in the cornea. If the
iris tissue adheres to the opening and acts as a plug, the anterior chamber
may refill and eventually the ulcer may heal and seal the opening in the
cornea. This could take many weeks to occur. In unfortunate
cases, the interior of the eye can become infected and eventually the eye
may be damaged beyond repair.
Once the cornea is abraded, the entire cornea suffers from
swelling (called edema) and the cornea takes on a slight haze. Then
tiny capillaries begin to move over the cornea from the white of the eye
(called the sclera) and seek out the damaged tissue. Within days of
the abrasion these tiny vessels are on their way to bring healing tissues
and fluid to the ulcer. As specialized corneal cells slide into and
fill the defect, the ulcer eventually heals and the surface of the cornea
returns to normal. Then the healing capillaries dry up and go away!
|