Exposes Highly Sensitive Nerves and Can Take Months to Heal

dog corneal ulcers

Story at-a-glance -

  • Corneal ulcers are a very common eye injury in dogs, and are typically caused by trauma to the eye, a foreign body, infection, dry eyes and abnormal structure of the eye
  • The seriousness of a corneal ulcer depends on how many layers of the cornea are involved
  • Symptoms of a corneal ulcer include squinting or pawing at the eye, watery eyes, sensitivity to light and a red, inflamed eye
  • Treatment depends on the underlying cause and the seriousness of the ulcer; ulcers that take a long time to heal can often be effectively treated with eye drops made from the patient’s own serum
  • Natural eye drops and other natural remedies plus an antioxidant-rich diet can also be very beneficial in both healing corneal ulcers and preventing their recurrence

By Dr. Karen Shaw Becker

The cornea of your dog's eye is the outermost covering or layer, and all the other parts of the eye, including the iris and pupil, lay behind it. The cornea is actually transparent (see-through) and admits light into the eye. It also serves as a barrier to protect the structures inside the eye from bacteria, chemicals, foreign objects or any other agent that could cause damage and interfere with your dog's vision. The cornea is composed of four layers:

  1. Epithelium, which is the outermost layer
  2. Basement membrane, which lies directly below the epithelium
  3. Stroma, which comprises most of the thickness of the cornea
  4. Descemet's membrane, which is the innermost layer

How Corneal Ulcers Occur

Wounds to the cornea, which are typically caused by an abrasion, scratch, puncture or other trauma to the eye, are called corneal ulcers. Other causes for ulceration include:

Foreign body in the eye

Inability to completely close the eyelids

Chemical burn

Entropion (eyelids fold inward)

Infection

Disease

Lack of adequate tears

Facial nerve paralysis

Corneal ulcers, which are sometimes called ulcerative keratitis, are a common eye injury in dogs (and cats), and they can cause a great deal of irritation and discomfort for your pet.

Typical Locations of Corneal Ulcers

A corneal ulcer can involve one layer up to all four layers. A mild or superficial ulcer involves only the epithelium, or outermost layer. Ulcers are considered severe or deep when they also affect the middle and innermost layers of the cornea. Superficial ulcers result in loss of a part of the epithelium layer. Deeper ulcers involving the stroma can cause significant scarring and perforation of the cornea.

When an ulcer extends through the stroma to the Descemet's membrane, a condition known as Descemetoceles, the problem is quite serious and can result in perforation. The location of a corneal ulcer depends to some extent on what caused it. An ulcer caused by trauma to the eye, dry eyes, bulging eyes or a paralyzed facial nerve is most often located in the center of the cornea.

If there is foreign matter trapped beneath the third eyelid, the corneal ulcer is usually seen toward the inside of the eye near the nose. If there is entropion or an unruly eyelash rubbing against the eye, the ulcer will often be seen in the peripheral cornea. An immune-mediated disease of the eye can cause ulcers at the borders of the cornea.

Symptoms

When the cornea of your dog's eye is injured, sensitive nerves are exposed. You may notice your pet's eye running or tearing more than normal, and she may squint or paw at her eye. There can also be sensitivity to light, a noticeable film over the eye, discharge or a red, inflamed, painful appearance. Your dog may also try to keep the affected eye closed.

Certain dogs, especially breeds with flat faces (brachycephalic breeds), are more prone to corneal ulcers. These breeds include the Boxer, Boston Terrier, Bulldog, Pekingese, Pug and Shih Tzu.

How Corneal Ulcers in Dogs Are Diagnosed

Diagnosis involves a careful examination of the eye and cornea, and direct observation of the ulcer using a diagnostic stain. The stain or dye allows your vet or veterinary ophthalmologist to check for erosions, ulcers or other injuries to the cornea. It will also indicate how deep the ulcer is into the layers of the cornea. Staining the eye also helps rule out other eye conditions with similar symptoms to corneal ulcers.

Other tests to determine the cause of your dog's eye problem can include a dry eye test, analysis of facial nerve function, cultures to look for bacteria or fungi, and blood tests to check for the presence of an infection. Unless your dog's corneal ulcer is mild (involving only the outer layer) and not caused by an underlying condition, or unless your veterinarian is very skilled in treating eye conditions, I recommend you ask for a referral to a veterinary ophthalmologist.

Treatment Options

Treatment of a corneal ulcer will depend to some extent on what caused the injury. Underlying conditions like dry eye, infection or disease must be resolved or treated along with the corneal injury to prevent recurrence of the ulcer. Treat­ment can include topical antimicrobial therapy, pain medication and drugs to control eye muscle spasms.

With proper care, superficial ulcers usually heal in a week or less. During treatment, your dog may need to wear an E-collar to keep his paws away from his eyes. Deeper, more serious ulcers may require sutures, conjunctival grafts, conjunctival flaps, the insertion of soft contact lenses or even a corneal transplant.

Oral antibiotics should not be part of your dog's treatment protocol, as they can't be absorbed in sufficient concentration to effectively treat or prevent infections of the cornea. Topical corticosteroids and anesthetics should also be avoided because they can prevent healing and often make the ulcer worse.

There is a type of corneal ulcer called a melting ulcer in which the stroma layer progressively dissolves. It is most often seen in pets with either a bacterial or fungal infection that produces enzymes that break down the corneal stroma. Complete loss of the stroma can occur in as little as 24 hours. Treatment includes antimicrobials, drugs to inhibit the action of destructive enzymes and in some cases, surgery.

There are also corneal ulcers known as refractory ulcers, indolent ulcers or Boxer ulcers. These are superficial ulcers that don't heal well and tend to recur, and may be caused by an abnormality in the basement membrane of the cornea. The ulcers weaken the epithelium surrounding them, which can be easily peeled back.

Refractory corneal ulcers are usually seen in middle aged or older dogs and tend to develop in both eyes at different times. They are seen in a wide variety of breeds, especially flat-faced (brachycephalic) dogs like the Boxer.

These ulcers can take months to heal. Topical antimicrobials and pain medications are given on an as-needed basis. Loose epithelium must be removed under topical anesthesia to allow healing to progress. Sometimes more invasive treatment is required, including a keratotomy, which involves cutting or piercing the cornea to promote attachment of new epithelium.

Another topical treatment that can be beneficial in treating long-standing ulcers are eye drops made from the patient's own serum. Many integrative veterinarians find the drops work better than the drugs often prescribed for these types of ulcers. There are also some natural eye drops that can be very beneficial at rapidly stimulating epithelial cell growth, including drops containing glycosaminoglycans such as chondroitin sulfate, N-acetylcysteine and aminocaproic acid solutions formulated specifically for the eye.

Feeding dogs with chronic ulcers an antioxidant-rich diet is also something I recommend, including foods naturally high in vitamin E, beta-carotene, selenium and omega-3 fatty acids. Integrative veterinarians can also suggest helpful Chinese herbs and a wide variety of nutraceuticals that are beneficial for eye health. These natural remedies can help ulcers heal, and also discourage recurrence.