What are Pigmentary Keratitis?
Pigmentary keratitis, also called corneal melanosis, is a condition in which light brown to black pigmentation covers part or all of a dog’s cornea, the clear covering at the front of the eye. A result of repeated irritation, inflammation or infection, the condition is seen most often in pushed-in nose breeds like Pugs or Boxers due to their facial characteristics that result in protruding eyes and wide eyelid openings that are exposed to injury or infection.
While there is no known cure for the condition except treating the inflammation’s cause, it can often be managed successfully with veterinary care. If the underlying cause is left untreated, pigmentary keratitis can lead to blindness.
Symptoms of Pigmentary Keratitis in Dogs
The most prominent symptom is a visible pigment deposit within the cornea. Sometimes it can be seen in normal light, or it may need a closer look. It may appear in one or both eyes. Other symptoms that are related to an underlying cause may include:
- Tearing, with dry-appearing cornea
- Large, swollen blood vessels in the conjunctiva (white part of eye)
- Ropy discharge
- Enlargement of the eye
- Redness of the conjunctiva
Causes of Pigmentary Keratitis in Dogs
Pigmentary keratitis is the direct result of repeated irritation and inflammation from structural, environmental, or infectious conditions. The pigmentation is formed when chronic inflammation prompts the collection of melanin granules that embed and darken the innermost layer of the cornea. Most commonly, this condition is seen in brachycephalic breeds including Pugs, Boxers, Bulldogs, and French Bulldogs.
There are several possible causes of inflammation that can cause pigmentary keratitis, including:
- Entropion – eyelid that rolls inward
- Ectropion – eyelid that rolls outward
- Abnormal eyelash position
- Eyelid tumors or other growths
- Traumatic injury
- Chronic, repetitive corneal ulcers
- Abnormal blink reflexes
- Previous eye surgery
- Dry eye syndrome
- Autoimmune disease
- Fungal or bacterial growth
Diagnosis of Pigmentary Keratitis in Dogs
Sometimes a pet parent will notice the eye discoloration and bring their dog to a veterinarian. At other times, there is no obvious outward sign, but the vet discovers the pigment during a thorough routine examination. An exam of the corneal surface with a lighted ophthalmoscope may bring it into sharper focus and reveal signs of trauma.
During the exam, the vet will also look for eye conditions that may be causing the inflammation. A Schirmer Tear Test may reveal a chronic dry eye, ulcers can be seen with a fluorescein stain, and eyelid or lash malformations may be readily apparent. Glaucoma can be detected with a test for intraocular pressure, and if an infection is suspected, cultures may be sent to the lab to look for fungi or bacteria.
Treatment of Pigmentary Keratitis in Dogs
Treatment of the condition is directed toward the underlying cause of the corneal inflammation. Each condition is treated by a veterinarian or veterinary ophthalmologist.
Surgery may be performed on dogs to repair eyelid malformations like entropion and ectropion. A procedure called a canthoplasty is aimed at removing lashes that are growing incorrectly or in the wrong location on the eyelids.
At one time, surgery was done to remove the discolored areas of the cornea, but this proved to present too much opportunity for complications like scarring and infection, and it was not a permanent cure unless the underlying cause was resolved. The use of cryosurgery to freeze and remove the discolored tissue was shown to be effective, but also was not a permanent solution.
Any medication carries a risk of side effects or allergic reactions, but several drugs have shown promise in the treatment of the underlying causes of pigmentary keratitis in dogs.
Fungal infections may be treated with antifungal medications such as voriconazole, applied directly to the eye or administered orally. A bacterial infection is similarly treated with antibiotic ointment or oral medication. The duration of treatment is typically ten days to two weeks.
If the dog is discovered to have glaucoma, which will cause a bulging eye exposed to inflammation, medications are given for the duration of the dog’s life to control the intraocular pressure.
Topical antibiotics and pain medication are administered if corneal ulcers are present, with healing typically within five to seven days. The veterinarian may also apply a soft contact lens to protect the cornea and alleviate pain. Severe, untreatable ulcers may require a corneal transplant or conjunctival grafts.
Corticosteroids injected under the conjunctiva, along with steroid eye drops, are 85% successful in treating chronic inflammation caused by autoimmune disease.
Medications for dry eye syndrome, such as artificial tears or prescription drugs aimed at increasing the production of tears, will create a fluid film on the dog’s eyes to protect them from irritants. Finally, drugs such as tacrolimus or cyclosporine can be used to decrease pigmentation and prevent its progression by correcting dry eyes.
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Recovery of Pigmentary Keratitis in Dogs
Lifelong, consistent medical treatment is necessary to address pigmentary keratitis in dogs. Frequent follow-up visits to the veterinarian will allow them to assess the effectiveness of treatments and monitor any new lesions or progression of old ones.
Environmental and behavioral changes may be recommended, especially those that may cause chronic irritation and inflammation of the eyes. When riding in a car, the pup should not be allowed to hang their head out of the window because of potential injury from insects, dust, and pebbles. Dog goggles are available to protect eyes if the dog will tolerate them.
In the case of infections, there is usually a good prognosis, but with corneal ulcers the outcome will depend on their severity. Resolution of the ulcers’ cause is necessary to improve outcomes.
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Cost of Pigmentary Keratitis in Dogs
Average cost of treating pigmentary keratitis: $250 - $2,000