Corneal ulcers are defects in the outer layers of corneal epithelium and are one of the more common eye disorders in domestic dogs.
Causes & Prevention
How Corneal Ulcers Affect Dogs
Ulceration of the cornea is extremely painful. Corneal ulcers can appear suddenly or slowly. The dog may have a history of recent trauma (hit by car, kicked by horse, etc.). The most universal signs of corneal ulcers are squinting, excessive tearing and rubbing at the eye(s), either with their paws or often by rubbing their face on the ground. Affected dogs may be intolerant of light. Over time, dogs with corneal ulcers can become depressed, lose their appetite and become lethargic. Owners may notice that their dogs' eyes are red and swollen, that their pupils are smaller than normal or that the eye surface seems cloudy. In more serious cases, corneal ulcers can actually rupture, causing a frightening discharge of pus and/or blood to come out of the eye.
Causes of Corneal Ulcers in Dogs
Corneal ulcers can be caused by a number of things, including trauma, foreign bodies, eyelid conformational abnormalities, tear production disorders and chronic infection. There is no age or gender predisposition to developing corneal ulcers. They are especially common in Boxers and other breeds with short noses, flat faces and broad foreheads. Other risk factors include dogs that are highly excitable, are prone to fighting or are used for hunting or otherwise spend time in heavy brush.
Preventing Corneal Ulcers in Dogs
The best way to prevent corneal ulceration and abrasion is to identify, avoid and/or treat the underlying cause of the condition.
The outlook for dogs with corneal ulcers is good as long as they are diagnosed and treated in a timely manner. One of the biggest complications of corneal ulceration is the increased risk of bacterial infection of the eye, which can cause permanent scarring and even blindness.
Symptoms & Signs
Corneal ulceration, which is a defect in or damage to the outer layers of the eye, is one of the most common and painful ocular disorders in domestic dogs. The majority of symptoms associated with corneal ulcers develop in response to irritation, inflammation and pain. In some cases, physical changes to the affected eye are apparent even to owners.
Corneal ulcers in dogs are divided into 3 general categories:
Simple/uncomplicated corneal ulcers: acute (sudden) loss of the outer layers of the cornea caused by minor trauma (shampoo, self-induced trauma, eyelash or eyelid abnormalities, etc); these usually heal readily, with minimal treatment or scarring;
Complex/complicated/deep corneal ulcers: acute or chronic (occurring over time) damage to the cornea, usually from trauma or infection;
Indolent/refractory corneal ulcers: chronic, superficial damage to the outer corneal epithelium in dogs of unknown cause; also called "superficial corneal erosion syndrome."
Symptoms of Corneal Ulcers
Ulceration of the cornea is extremely painful. Corneal ulcers can develop suddenly or slowly, although acute onset is more frequent. Occasionally, there is a history of recent trauma (hit by car, kicked by horse, etc.), although most of the time the owner has not witnessed any traumatic incident.
The most universal signs of corneal ulcers include the following:
Tearing and tear-staining around the eyes
Rubbing at the eyes, either with paws or by rubbing and scooting the face along the ground
Intolerance of light; shying away from bright light (called "photophobia")
Lack of appetite (anorexia; inappetance)
Red, swollen eyes (corneal edema)
Cloudy eye surface
Small pupils (myotic pupils)
Bloody discharge from eye
Pus discharge from eye
As corneal ulceration becomes more chronic, the signs of pain tend to decrease. The rubbing and pawing by dogs with corneal ulcers unfortunately can prolong or even prevent healing and can further damage the cornea. If you notice these signs in your dog, make a prompt visit to your veterinarian, who after examining your dog may refer you to a veterinary eye specialist (ophthalmologist).
Dogs At Increased Risk
There is no age or gender predisposition to development of simple or complex corneal ulcers. They are especially common in Boxers and other brachycephalic breeds with short noses, flat faces and broad foreheads. Other risk factors include dogs that are highly excitable, are prone to fighting (especially with cats) or are used for hunting or otherwise spend a lot of time outdoors romping through heavy brush. Dogs with bulging eyes also are at an increased risk, including the Pekingese, Maltese, Boston Terrier and Pug, among others. Refractory or indolent corneal ulcers tend to be seen more frequently in middle-aged to older neutered or spayed dogs, although they too can occur at any age or in any breed. Breeds that seem predisposed to developing indolent corneal ulcers include the Boxer, Samoyed, Dachshund, Miniature Poodle, Pembroke Welsh Corgi, Wire Fox Terrier and Shetland Sheepdog.
Diagnosis & Tests
Many corneal ulcers are visible to the naked eye, and they are not especially difficult to diagnose. There are several diagnostic tests that can confirm the presence of ulcerations or other injuries to the cornea of companion dogs when they are not easily seen.
How Corneal Ulcers are Diagnosed
When a dog presents with ocular pain, irritation and inflammation, the veterinarian will conduct a thorough physical examination, as well as a neurologic and ophthalmic examination to assess the dog's vision and visual reflexes. She will probably assess intraocular pressure to rule out glaucoma, and may take samples for culture and sensitivity in case infection is present. Application of topical fluorescein dye is one of the most conclusive diagnostic tests for corneal ulcers. The damaged corneal tissues will pick up the dye, making diagnosis quite easy and allowing the veterinarian to assess ulcer depth. A Schirmer tear test may also be recommended to measure aqueous tear production. Many times, corneal ulcers can be seen without any special diagnostic tools or techniques. They appear as dull spots, or dish-like depressions, on the outer surface of the eye ball.
Ulceration or abrasion of the cornea requires veterinary attention. Even simple corneal ulcers can rapidly become complex, deep injuries that can ultimately lead to blindness. Eye injuries are always serious. If owners suspect that their dog is experiencing impaired vision or has other signs of damage to the eyes, a quick trip to the veterinary hospital is necessary.
All corneal injuries should be treated by a veterinarian. Emergency surgery may be necessary to save the eye. The type and level of treatment for canine corneal ulcers depends upon their severity. The goals of treatment are to prevent progressive loss of corneal tissue, eliminate pain, prevent or resolve any infection, promote regrowth of healthy corneal tissue, minimize scarring of the cornea, and of course prevent blindness. Superficial, simple ulcers usually can be treated with prescription eye drops on an outpatient basis. Complex, deep or refractory corneal ulcers require much more extensive medical - and normally surgical - treatment.
Treating Corneal Ulcers in Dogs
Simple, superficial corneal ulcers normally are treated with topical broad spectrum antibiotic and/or antifungal eye drops or ointments to manage infection, together with topical medication to help reduce pain, such as atropine. Sometimes, systemic oral non-steroidal anti-inflammatory drugs (NSAIDs) will be added to the mix. For slightly more severe ulcers, the veterinarian may apply a therapeutic soft contact lens to affected eyes and an Elizabethan (cone) collar to protect the eyes while they heal. The patient should be confined indoors, except for occasional leash walks for exercise and to potty, until the ulcers are completely healed. Bright light should be avoided. The veterinarian will want to recheck progress at regular intervals, especially if a contact lens is used as part of the treatment protocol.
It is important for owners to follow their veterinarians' treatment regimen to the letter. Simple corneal ulcers can quickly become complex. If they do not heal within one or two weeks of aggressive medical treatment, there may be an underlying problem such as a weak attachment of the cornea to the basement membrane of the eye. Treatment will then need to progress as for deep, complex corneal ulcers.
Complex corneal ulcers usually require all of the treatments described above for simple ulcers, followed by surgical intervention to save the eye. Depending upon the cause of the ulcers, topical treatments may be tried before surgery. These currently include a number of strong antibiotics, antifungal drugs and possibly "autogenous serum," prepared from a sample of the dog's own blood. If none of these resolve the problem, surgical repair is the next option.
There are a number of surgical techniques to correct corneal ulcers, and more are being developed all the time. Generally, these procedures involve removing the damaged or diseased portion of the cornea and, if necessary, placing some form of corneal or conjunctival graft over that area. Surgery must be followed by long-term treatment with topical antibiotics, anti-pain medication and possibly soft contact lenses, topical tear supplementation and bandaging.
As long as owners are diligent in complying with all recommended treatments, both before and after any surgical procedure, the prognosis for recovery from corneal ulceration is quite good.