Corneal ulceration is one of the most common eye diseases in the dog and cat. The cornea is a transparent, very thin covering over the front of the eyeball. It is less than 1mm thick and is multi-layered like an onion. The cornea has numerous nerve endings and is extremely sensitive. It readily reacts to irritants from both outside and inside the eye.

The healthy cornea is normally very resistant to infection. When the cornea becomes injured, it loses its transparency and may become partially or totally cloudy. Corneal cloudiness may be caused by trauma, allergic reactions, infection (viral and bacterial), birth defects, metabolic/endocrine disease, chemicals and other irritants. If an injury occurs which damages the cornea, it may allow bacteria to penetrate, causing an infection in the deeper layers of the eye.

A corneal ulcer is an erosion through one or more layers of the cornea. Rapid deterioration of the cornea may result in very serious disease, even blindness. The scientific name for this condition is "Ulcerative Keratitis."

Corneal ulcers result in pain, blepharospasm (eyelid blinking), scleritis (reddening of the white part of the eye), conjunctivitis (inflammation of the pink tissues), sensitivity to bright light and discharges from the eye. Blindness or potential loss of the eye can result if the ulcer is not properly treated.

Sometimes an ulcer on the cornea cannot be seen with the naked eye. A special stain must be used to assess the size and severity of the erosion. Treatment is based upon the severity of the erosion and may range from topical antibiotics to surgery for deep infections. Corneal ulcers are classified based upon what caused it and how deep the ulcer is.

Simple superficial corneal ulcers usually occur secondary to minor trauma, self-induced trauma, shampoos, eyelash abnormalities, eyelid deformities and tear film disorders. They usually resolve within 5 to 7 days with topical antibiotic ointment applied three to four times daily to prevent bacterial infection. Never use topical or oral corticosteroids (Prednisone, Dexamethasone, Betamethasone) with ulcerated corneas. Steroids delay wound healing and can cause a superficial ulcer to rapidly become a deep one and potentially cause the eye to rupture.

Corneal ulcers caused by underlying eyelash (distichiasis) or eyelid deformities (entropion/ectropion) will need to have corrective surgery of the underlying problem or the ulcers will recur.

Deep corneal ulcers may need minor surgery such as a corneal or conjunctival flap to provide additional support. Topical therapy will also be required. Descemet’s membrane is the innermost layer of the cornea. A desmetocele is a bulging of the membrane after a deep ulcer has eroded all of the above corneal layers. This is an emergency and requires surgery. Failure to treat this disease in a timely manner can result in rupture and collapse of the eyeball.

Persistant or refractory corneal ulcers are superficial ulcers that heal poorly or slowly and also tend to recur. Typically, an overlapping lip of undermined epithelium is present, preventing the ulcer from granulating in (healing). These occur because of an abnormality in the corneal stroma. These have also been called a ‘Boxer ulcer’ because it was originally described in that breed. Refractory ulcers can also be caused by certain bacteria that secrete collagenases, resulting in what is called a melting ulcer. Melting ulcers are commonly seen in brachycephalic breeds (e.g. Boxers, Bulldogs). Because of the underlying stromal deficiency, healing of refractory ulcers may take weeks to months and recurrence is not uncommon. Treatment involves topical therapy with periodic epithelial debridement and punctate or grid keratotomy.

Notify the Doctor if any of the following occur:

• You cannot apply the medicine as directed. 

• Sutures (if present) loosen or become lost.

• Your pet shows signs of continued or worsened discomfort. 

• You notice a bulging of the cornea (desmetocele) where the ulcer is or the ulcer appears to be getting larger or deeper.

• You can see the eyeball after a third eyelid or conjunctival flap surgery has been performed.

Note: This article is provided by Claws & Paws Veterinary Hospital® for informational purposes only.