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| INDEX OF ARTICLES | WAITING ROOM | EXAM ROOM | SURGERY ROOM | X-RAY ROOM | GENERAL TOPICS | IMPORTANT TOPICS | LAB and PHARMACY | PET PHOTOS | PET SUPPLIES | PET PHARMACY |
Corneal Ulcers in Dogs and Cats
Click image to see close up
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!
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Fluorescein strips are used to demonstrate if there is a break in the corneal surface. The stained strip is moistened with sterile water and the stain is flushed across the eye. Any break in the corneal surface takes up the stain and the veterinarian can record the dimensions of the defect. |
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Materials Used In An Ocular Exam |
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Materials commonly used to diagnose a corneal ulcer are shown below. On the left is a topical anesthetic to temporarily eliminate the pain associated with the ulcer and to allow thorough examination of the eye. The Shirmer Tear Test is used to measure tear flow in the eye. Fluorets are the little paper strips that contain the stain that demonstrates the corneal defect. The ophthalmoscope is used to highlight the cornea and to allow examination of internal structures of the eye. The Schiotts Tonometer is at the bottom of the image and is used to evaluate intraocular pressure. It is not commonly used during the evaluation of the corneal ulcer unless there is evidence that there may be an underlying pressure problem with the eyes such as Glaucoma. |
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Example of a case of an ulcerated cornea... |
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This Lhasa Apso was
presented because of squinting, watery eye, and pawing at the eye. The
stain demonstrates on the right the extent of the ulcer and the new
blood vessels (called neovascularization) that are supplying the area
with healing nutrients. |
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Treatment For Corneal Ulcers In Dogs
and Cats
Most veterinarians will begin treating
corneal ulcers in dogs and cats with appropriate antibiotic ointment or
drops. The use of cortisone or cortisone-related medications may not be a
good choice to use due to the possibility of delayed healing and a worsening of
the ulcer. It pain is evident, Atropine or other antispasmodic medications
may also be dispensed. The dog or cat's dewclaw, if present, may need to
be bandaged to prevent the dewclaw from doing further damage to the irritated
cornea as the patient wipes across the offending eye. Rechecking the eye
in five days and then another five days usually demonstrates that proper healing
has taken place. A negative stain uptake upon use of the Fluorescein stain
will indicate if additional treatment is needed.
Some breeds of dogs, notoriously Boxers and Boston Terriers, often have very unresponsive corneal healing activity. These cases of poorly healing corneal ulceration need to be monitored closely and special selection of adjunctive medications, such as topical Vitamin E and other medications, may need to be tried to stimulate corneal epithelium regeneration.
Third eyelid flap surgery
Occasionally when a corneal ulcer fails to heal or when a
very deep or wide ulcer is present a third eyelid flap procedure is performed.
Under general anesthesia the patient's Nictitating Membrane...also spelled
Nictating Membrane... (called the
third eyelid) that originates in the medial corner of the eye opening and under
the lower lid, is pulled up and over the cornea. It is sutured to the
inside of the upper eyelid, thus forming a protective and nourishing layer
of tissue over the damaged cornea. Medications can still be applied to the
eye between the eyelids, but the surface of the cornea will not be exposed and
cannot be visualized while the third eyelid flap is in place. The sutures
are removed in 10 to 28 days and the corneal healing is assessed. This
procedure is commonly done and be very helpful in generating a healing response
in severely damaged corneas.
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Other interesting topics in veterinary ophthalmology |
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