Pigmentary Keratitis In Dogs

Pigmentary Keratopathy / Keratitis (PK) in the dog is due to the migration of pigmented melanin granules onto the cornea associated with chronic inflammation. This is a frequent cause of blindness in brachycephalic dogs.

PK is a clinical condition in which infiltration of inflammatory cells to various corneal layers in response to harmful stimuli, such as own-antigens or contagious exogenous agents. The inflammatory response may cause corneal edema, infiltration of inflammatory cells, corneal epithelium suppurative melting, and ciliary congestion.

Migration of pigments to the cornea is often associated with the occurrence of blood vessels and it is termed pigmentary vascular keratitis.

Pigmentary keratitis can also be seen in association with keratoconjunctivitis sicca (KCS). KCS is characterized by chronic corneal inflammation, lacrimal gland, and conjunctiva, secondary to a deficiency of the precorneal tear film (PTF). Commonly referred to as dry eye syndrome, this condition is due to the lacrimal gland and/or nictitans gland’s insufficient production of the aqueous portion of the tear film.

Initial Stage:

• Excessive Blinking
• Painful, Red, and Irritated Eyes
• Mucoid to mucopurulent ocular discharge

Intermediate Stage:

• Corneal Ulceration
• Corneal Scarring
• Conjunctival Hyperemia
• Secondary bacterial infections may also occur

Final Stage:

• Hyperpigmentation
• Corneal Perforation
• Neovascularization
• Fibrosis
• Blindness

The objective of PK treatment is two-fold: to improve function and prevent further corneal damage.

Treatment can be divided into two modalities - medical and surgical.

Medical treatment consists of improving the stability, quantity, and quality of the tear film.

Surgical procedures to remove pigmented sections of the cornea are mostly not beneficial due to the recurrence factor.

Sometimes, immunosuppressive therapy (medications that suppress the immune system) with corticosteroids may be necessary.

1. Artificial tear drops are used. Artificial tear drops substitutes are hyaluronic acid, polyvinyl alcohol, polyvinyl pyrrolidine, and methylcellulose.
2. Cyclosporine A (CsA) - CsA disrupts the immune-mediated reaction against the cornea, conjunctiva, and lacrimal glands. Even for normal eyes, it acts as a lacrimomimetic agent and has an anti-inflammatory effect too.
3. Noncytotoxic immunosuppressants - pimecrolimus, and tacrolimus.
4. Acetylcysteine: A mucolytic agent to treat mucin excess on the ocular surface.
5. Pilocarpine: Used to treat KCS with neurogenic origin (parasympathomimetic agent)

• Gently washing the eyelids using baby shampoo and/or applying warm compresses to the eyes can help discharge the oil in the tear glands.
• Pet eye lubricating gels are another option (best to apply at night or before bedtime).
• Supplementing for healthy eyes - help your dog have healthy ocular hygiene with supplements.
• Make your dog more comfortable: Cleanse eyelids to remove crusts (dried discharge) with lukewarm water with a half-teaspoon of salt.
• Use physiological saline or a commercial eye cleansing agent: (such as Eye Scrub) or lactated Ringer’s solution.

Check your dog on a regular basis and consult your veterinarian immediately if you find any odd changes in eye color associated with a dark film across them.

Brachycephalic Dog Breeds, Bloodhound, Cocker Spaniel, Cavalier King Charles Spaniel, Lhasa Apso, Miniature Schnauzer, Pekingese, Samoyed, West Highland White Terrier, Yorkshire Terrier, Boxer, Shih Tzu, Pug, English Bulldog, French Bulldog, Boston Terrier

1. Causes:

A. Infectious Keratitis:

• Bacterial Keratitis - such as Staphylococcus, Streptococcus, Pseudomonas, Nocardia, and Moraxella.
• Fungal Keratitis - Aspergillus, Cladosporium, Candida (yeast), Fusarium, Microsporidia, Alternaria and Curvularia.
• Protozoal Keratitis - Protozoal keratitis and conjunctivitis (Acanthamoeba keratitis).
• Viral Keratitis - Canine Herpes Virus(CHV), Canine Distemper Virus.
• Keratitis by Oomycete - Parasitic Aquatic Oomycete (Pythium Insidiosum).

B. Noninfectious Keratitis:

• Tear deficiencies, aberrant hairs, and poor eyelid closure.
• Metabolic: Hypothyroidism and Diabetes Mellitus.
• Neurogenic: Middle-aged female dogs - associated dry/crusted ipsilateral nostrils.
• Iatrogenic: In the case of “cherry eye”, surgical removal of the gland of the third eye.
• Immune-Mediated: Predominant cause.

2. Types:

Infectious Keratitis - An infection caused by fungi or bacterium results in inflammation of the cornea. Prominent symptoms are Eye redness, Excessive tearing, Eye discharge, etc.

Ulcerative Keratitis - Inflammation due to a trauma/injury to the cornea surface, can lead to the cornea stroma. Squinting, Excessive tearing, Sensitivity to light, etc.

Chronic Superficial Keratitis (also called pannus) - This is an autoimmune, progressive, inflammatory condition of the cornea. Usually affects Border Collies, Labrador Retrievers, German Shepherds, and Greyhounds.

3. Morbidity:

Pigmentary Keratitis is rare in dogs. Incidence in dog population data is not available.

4. Mortality:

There is no mortality due to this condition documented yet.

5. Diagnosis:

• Schirmer Tear Test (STT)
• Fluorescein Staining Test
• Tonometry
• Aesthesiometry
• An Electroretinogram
• Ultrasound

6. Prognosis:

PK isn't a lethal condition, but it can ultimately lead to eye problems. Discuss with your vet to figure out the underlying cause.

Depending on the cause, PK can be treated with either medication to keep the eyes moisturized or surgery.

Contact your vet right away, if you notice any of the following:

• If your dog blinks excessively or the eyes look painful and red continuously.
• Watery Discharge / Excessive Tearing.

The diet should be included foods containing Vitamins A, and C, Omega-3 fatty acids, Zinc, Carotenoids, Beta-carotene, Lycopene, Glutathione, Phytonutrients - and the special partnership of Zeaxanthin and Lutein (natural sunblock).

• Pick seafood over the usual beef and chicken.
• Omega-3 oily fishes such as salmon, tuna, cod, etc.
• Leafy greens such as spinach, kale, watercress, etc.
• Nonmeat / plant protein sources such as nuts, Lentils, Beans, Eggs, etc.
• Citrus fruits or juices.
• Sweet potatoes, Tomatoes, Pumpkin.
• Pork, Tuna, Oysters.
• Blueberries, Broccoli, Cabbage, Carrots.

For pets with PK, Early diagnosis with prompt treatment, as well as routine follow-up examinations is of paramount importance. In most dogs, the prognosis can be excellent with the maintenance of vision and long-term comfort.