Overview of Canine Corneal Ulcerations
Corneal ulceration is a common condition in dogs and is loss of the corneal epithelium (the outermost cells of the cornea) with exposure and possible loss of the underlying corneal collagen. Corneal epithelium is constantly being lost and replaced, and its health and thickness depend on a delicate balance between a dog’s cell loss and regeneration.
Causes of excessive cell loss include injury from ingrown or misplaced eyelashes, exposure to foreign material, chemicals, heat or smoke, infections with certain viruses and bacteria, and from trauma such as cat scratches. Decreased tear production (“dry eye” or keratoconjunctivitis sicca) and inadequate blink responses may cause corneal ulceration. The potential causes of corneal ulcers are almost too numerous to list.
Corneal ulceration can affect any animal; however, those breeds of dogs with more protuberant (prominent) eyes and larger eyelid openings are at increased risk. Some older animals may heal more slowly and, therefore, have ulcers that may be more difficult to treat.
Corneal ulceration is a painful and potentially vision-threatening condition. Early diagnosis and appropriate treatment is usually rapidly curative. Complicated cases can progress to full thickness or perforating ulcers with serious effects on vital structures within the eye.
What to Watch For
Mucus or pus draining from the eye
Cloudiness of the cornea
Inflamed, red conjunctiva (the normally pink tissue surrounding the cornea and lining the eyelids)
Inability to see the eye because the third eyelid is covering it
Rubbing at the eye
Veterinary care includes diagnostic tests and subsequent treatment recommendations.
Diagnosis of Corneal Ulceration in Dogs
Diagnostic tests are needed to recognize corneal ulceration, any underlying cause and to exclude other diseases. Tests may include:
Thorough ocular examination with special attention to the eyelashes, eyelids and blink reflex, status of the cornea and the interior of the eye
Fluorescein staining of the cornea to assess ulcer size, depth and character. Fluorescein is a dye that adheres to the central layer of the cornea and makes the ulcerated area become bright green.
Schirmer tear test to measure tear production
Cytology, culture and antibiotic sensitivity testing of ocular samples for the presence of infectious agents such as bacteria
Treatment of Dogs with Corneal Ulcerations
Treatments for corneal ulceration may include any of the following:
Removal or treatment of the underlying cause
An antibiotic eye drop or ointment to treat or prevent infection of the cornea
Atropine to dilate the pupil and relieve pain from uveitis (inflammation of the inner layers of the eye) or spasm of the iris
An Elizabethan collar to prevent the patient from rubbing the eye and making the ulcer worse
Surgery to correct a rapidly progressive or deep corneal ulcer. Surgery may involve applying a soft contact lens or suturing the eyelids partially closed to bandage the eye, or the placement of conjunctival grafts over deep lesions.
Oral antibiotics for serious infections of the cornea, and oral anti-inflammatory drugs (such as aspirin) if inflammation is present within the eye
At home, administer all veterinary prescribed medications and follow-up with your veterinarian within several days of the original diagnosis. Take care that your dog doesn’t rub at the eye or cause any extra trauma to the healing ulcer. Leave the Elizabethan collar on at all times until your veterinarian approves its removal.
Observe the eye for signs of worsening, especially cloudiness of the cornea, increased or altered ocular discharge, continued squinting, or more obvious redness of the conjunctiva, which is the white tissue lining in the eyelids and covering the eye).
Examine your dog’s eyes regularly and call your veterinarian if you note any pain or color change. Pay particular attention to your dog’s eyes after he has been running through long grass or brush. If your dog is a hunting or field-trial dog, then examine his eyes after he returns from the field.
Try not to get anything other than saline or clean water in your dog’s eyes. For example, avoid shampoos, soaps and any other household cleaners. Do not attempt to remove foreign material from your dog’s eye. Instead, seek urgent veterinary care.
Related Symptoms or Diseases to Corneal Ulceration in Dogs
Your veterinarian is usually able to diagnose corneal ulceration with a thorough examination and application of a fluorescein dye to your dog’s cornea. However, discovering the cause of the ulceration and checking for related ocular abnormalities can be challenging. The following conditions may be causes or effects of the corneal ulcer:
Eyelash abnormalities. Extra eyelashes (distichia) and/or misdirected eyelashes (ectopic cilia) may cause corneal ulcers, especially in younger purebred dogs. These eyelashes may rub directly on the cornea.
Eyelid abnormalities. Rolling in of the eyelid/s (entropion) and/or inability to completely close the eyelids when blinking (lagophthalmos) may cause or exacerbate corneal ulceration. Entropion may be inherited or acquired following injury or inflammation. Entropion causes eyelashes and or hair from the lids to rub across the cornea. Lagophthalmos may develop following injury to the nerves responsible for blinking and is occasionally inherited in dogs with flat faces and protuberant eyes.
Keratoconjunctivitis sicca (“dry-eye”). Inadequate production of the watery tears or a deficiency in any of the tear film components can cause the surface of the cornea to become more susceptible to infections and environmental irritation. The tear film is a very important protective mechanism for the eye..
Uveitis is seen frequently with more serious ulcers. The pain associated with corneal ulcers causes inflammation within the eye. This inflammation is accompanied by the release of substances within the eye and subsequent uveitis. The uveitis usually resolves once treatment for the ulcer is instituted, but your veterinarian may also recommend specific treatment for the uveitis.
Your veterinarian will do a complete medical history and perform a thorough ophthalmic examination. Thorough examination provides essential information regarding the cause, duration, and severity of the corneal ulcer. It may also highlight other related symptoms or diseases such as those listed above. Parts of the examination are often conducted in a darkened room using a bright light source and some form of magnification.
As part of the examination, fluorescein stain is applied to the cornea and any excess is rinsed off. Fluorescein stain adheres to any areas where the surface layer of the cornea is missing. It outlines the ulcer and permits accurate assessment of the size and depth of the ulcer.
If low tear production is suspected as the cause, a Schirmer tear test is performed. A small strip of calibrated filter paper is placed inside the lower eyelid and left in place for one minute. The distance to which tears flow along this filter paper is a measure of the volume of tears produced. .
Your veterinarian may assess your dog’s blink reflex. This involves a gentle tap with the finger at the corners of the eye and observation of the completeness and speed of eyelid closure. Be sure to tell your veterinarian if you have seen your dog sleeping with his eyelids partly open, thus potentially exposing the middle of the cornea to drying.
In cases where the ulcer appears infected, special samples may be collected from the cornea for examination under a microscope, for bacterial culture, and for antibiotic sensitivity testing. This is particularly important if an ulcer has progressed rapidly or has failed to respond to appropriate antibiotics.
If special techniques, equipment, and/or training are required, your veterinarian may refer your dog to a veterinary ophthalmologist for further evaluation.
Treatment In-depth for Dogs with Corneal Ulcerations
The principal goals in the treatment of corneal ulceration are to identify and treat its cause, to prevent secondary infection, and to encourage healing. Following removal of the inciting cause and appropriate treatment, repair of minor corneal ulcers is often complete within seven days. Patients with slow-healing or rapidly progressive ulcers require more protracted therapy.
The typical therapeutic approach to ulcers may include any of the following:
An Elizabethan collar may be applied. Corneal ulcers can be irritating and your dog may cause more serious injury to the eye if she scratches it with her paws or rubs it against carpet or furniture.
Bacteria are regularly implicated in the worsening of corneal ulcers, particularly ulcers that get deeper. Therefore, one of the most important treatments for corneal ulcers is the prevention of secondary infection with the application of a topical ophthalmic ointment or eye drop to the eye until the ulcer is healed. One of the more commonly used preparations is a combination of three antibiotics – neomycin, polymyxin, and bacitracin or gramicidin. In more serious ulcers, antibiotic choice is guided by culture and sensitivity results. It is critical to avoid the topical use of any medications containing corticosteroids when the cornea is ulcerated.
If an ulcer is deep when it is first detected, or if it progresses rapidly despite appropriate treatment, surgery may be necessary to save the eye and vision. This commonly involves referral to a veterinary ophthalmologist.
The most commonly performed surgery for deep corneal ulcers or ulcers that are threatening to perforate the eye is a conjunctival graft performed with the patient under general anesthesia. A small piece of the conjunctiva that surrounds the cornea is sutured into the ulcer. This brings a healthy blood supply to the area and provides mechanical support to the diseased cornea. Grafting decreases the chances of perforation, increases ocular comfort, and speeds healing, similar to what a skin graft does for a severe burn.
For more superficial ulcers, a bandaging type of procedure may be enough to encourage healing. Sometimes a soft contact lens is placed on the eye. The lens covers the ulcer and keeps it protected. If contact lenses are not available, the third eyelid may be temporarily sutured to the top lid so that it covers the cornea. While suturing the third eyelid up also protects the cornea, the cornea is hidden so it is not possible to observe whether the ulcer is improving or worsening. The animal can see through a contact lens, but it cannot see through the third eyelid while it is sutured up.
Another type of protective surgery is the partial tarsorrhaphy, where the external eyelids are temporarily sutured together. The lids can be partially closed, thereby protecting the cornea, but still permitting frequent observation and treatment of the ulcer.
Treatment of dry eye and other tear deficiencies, removal of additional or misdirected eyelashes, and surgical correction of entropion may be necessary in some cases.
Follow-up Care for Dogs with Corneal Ulcerations
Follow-up care of corneal ulcers is critical. Administer any prescribed medication(s) as directed and be certain to alert your veterinarian if you are experiencing problems treating your dog. Optimal follow-up veterinary care often involves the following:
Because uncomplicated ulcers often heal within seven days, all ulcers are rechecked within this time period. More serious ulcers or any ulcer that appears to worsen during treatment are checked sooner and more frequently. At the recheck examination, fluorescein stain is again used to outline the ulcer. Any ulcer that worsens despite appropriate therapy requires further investigation and may warrant referral to a veterinary ophthalmologist.
Recheck examinations may also be needed long after the ulcer has healed to monitor for the recurrence of underlying causes, particularly regrowth of eyelashes, possible return of normal blink responses, and changes in tear production.
In older dogs or boxer dogs of any age, certain superficial ulcers may persist for greater than 14 days and may be very difficult to resolve. Such ulcers are termed indolent ulcers or persistent corneal erosions. They require additional treatments from those listed above in order to heal.