Symptoms, Diagnosis and Treatment of Corneal Ulcers in Pets

By Dr. Amanda Corr, VMD, DACVO| Ophthalmology

Corneal ulcers occur in pets when they experience trauma on the surface layer of their eyes. This trauma can occur through abrasions, scratches, infection, and more, resulting in deeper layers of the cornea being lost. Here Dr. Amanda Corr, Ophthalmology, VMD, DACVO answers some of the most important questions about corneal ulcers in pets.

What is the cornea?
Dr. Amanda Corr: The clear, outer surface of the eye is called the cornea. It is often referred to as the ‘windshield’ of the eye and a healthy cornea is essential for normal vision. It is made up of many layers of cells which are arranged very specifically so that the cornea is crystal clear. The outer layers of the cornea are called the epithelium and are intimately attached to the deeper layers called the stroma. One of the most sensitive parts of the body, the cornea has many nerve endings for pain perception. However, it does not contain any blood vessels. Instead, the cornea receives oxygen and nutrition from the tears which are spread over the cornea when the animal blinks.

What is a corneal ulcer?
Corneal ulcers may also be called ‘scratches’ or ‘abrasions’ and are a very common eye problem diagnosed in pets. Ulcers are essentially open wounds within the cornea. If an animal’s cornea becomes ulcerated it can be very painful. Most ulcers heal within a week; however, certain types of ulcers may require specialized procedures to heal. If an ulcer becomes infected it can rapidly develop into a deep wound or perforation. What causes corneal ulcers in pets? There are many different reasons that an animal may have a corneal ulcer. Most commonly, an animal develops an ulcer due to trauma — they may be scratched while exploring outside, playing with another animal or aggressively rubbing their eye. A pet is at higher risk for corneal ulceration if they have an underlying condition such as a tear deficiency or an abnormally placed eyelash that may be rubbing on the cornea. Brachycephalic, or “short-headed,” animals such as the pug dog or Persian cat, are at higher risk for corneal ulcers due to increased exposure of the eye and poor blink coverage over the cornea.

What signs can you look for to determine if your pet may have a corneal ulcer and needs to be examined by the veterinarian?
The most common symptoms of a corneal ulcer are squinting, redness, and ocular discharge. Ulcers are typically painful, and the animal will squint, blink excessively, or even hold its eye completely closed. The normally white part of the eye (sclera) often becomes very red and may even be swollen. The front of the eye may become hazy or cloudy. Animals with corneal ulcers often have excessive tearing. If the ulcer is due to a tear deficiency, the discharge can even be thick like mucous ranging from clear to white, yellow, or green. Other symptoms that may be a sign of a corneal ulcer include: rubbing of the eye, a cloudy eye, and lethargy or decreased appetite if the animal is painful.

Any of these signs should prompt the owner to take their pet to the veterinarian and the pet should be checked for an ulcer. A simple test called a fluorescein stain test is used to diagnose a corneal ulcer. Fluorescein is a special stain dropped into the eye that attaches to an ulcer and can be seen with a specialized blue light.

How are corneal ulcers treated?
Corneal ulcers can be classified into ‘simple’ and ‘complicated.’ Most ulcers are simple, involve only the outer layers of corneal cells called the epithelium and heal within three to seven days. The body heals itself by sliding new healthy layers of epithelium over the wound and these layers attach to the deeper layers (stroma). Antibiotic drops or ointments are used to prevent an infection. Pain medications are often provided in the form of either a pill and/or a topical medication called Atropine. Depending on the underlying cause of the corneal ulcer, additional medications may be warranted. If the ulcer is complicated by infection, additional medications are also used at a greater frequency. An E-collar is always essential to prevent the pet from rubbing and allow the cornea to heal properly.

When do I know to stop giving my pet medicine for corneal ulceration?
The only way to know that the corneal ulcer has healed is by visiting the veterinarian who will repeat the fluorescein stain test. Once the veterinarian has confirmed healing, the medication is typically discontinued, and the E-collar can be removed.

What is an indolent corneal ulcer?
Indolent corneal ulcers are ulcers which do not heal in a normal way and within the normal time frame. In dogs, this type of ulcer may also be called a Boxer ulcer or spontaneous chronic corneal epithelial defect (SCCED). Indolent ulcers in dogs often occur due to an underlying defect in the cornea that prevents the outer epithelial cells from attaching to the deeper stromal cells. In cats, indolent ulcers are often due to a viral infection.

In order to allow healing of an indolent ulcer, a minimally invasive procedure may need to be performed by the veterinary ophthalmologist. This procedure is done using topical anesthesia. The first step involves debridement of the unattached epithelial cells using a dry sterile cotton swab. This clears the cornea of excessive, dead epithelial cells that are interrupting the healing process. Next, either a special instrument called a diamond burr or very small needle tip will be used to place small grooves within the stroma (keratotomy). This creates a roughened surface for new epithelial cells to attach on to and heal over. This second step, the keratotomy, should not be done in cats. Lastly, a soft bandage contact lens may be placed on the cornea to help facilitate healing. The contact lens will also provide comfort during the healing process. These procedures have an 85-95 percent success rate. Very rarely, an indolent ulcer requires a surgical procedure called a keratectomy which is done under general anesthesia.