Corneal Melanosis— A Threat to Your Pet’s Eyesight!

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As pet parents you would have melted into your pet’s eyes a million times & counting still. In our 99th issue we talk about how Corneal Melanosis can be threatening for the vision of your pets.  –by Dr Beenish Qureshi, Dr Deepti Sharma and Dr Harmanpreet Singh Sodhi

Dr Beenish Qureshi

Dr Deepti Sharma

Dr Harmanpreet Singh

Corneal Melanosis also referred to as Pigmentary Keratitis (PK) is a relatively common ocular disease in dogs. In this disease the cornea is affected and there is migration of brown pigment into the cornea. The pigment usually affects one or both eyes and can either cover a portion or whole of the cornea leading to decreased vision or ultimately blindness. It occurs more often in dogs and is rare in cats. Commonly affected breeds include Chinese Pugs, Pekingese, Shih Tzu, and Lhasa Apso.
Understanding the cause
It occurs in response to chronic irritation caused by extra or abnormal eyelashes (distichiasis, ectopic cilia), exposure of the cornea with eyelids wide open (lagophthalmos), nasal fold trichiasis, lack of tear production leading to dry eye, decreased blinking response, and sometimes after recovery from healing of corneal ulcers. Recent studies suggest immune mediated insult to cornea due to the ultra-violet rays leading to initiation of auto-immune process.

Be cautious of signs & symptoms
Depending upon the area involved by the melanocytes over the cornea your pet may show diverse clinical signs. Sometimes he may show no clinical signs except for the development of dark brown patch over a small corneal area. Clinical signs such as decreased vision may develop if pigment progresses to most of the cornea. Other signs which may develop include discharge, redness, corneal opacity, decreased stimuli to threatening gestures, granulation tissue formation etc.

Timely diagnosis is pivotal
Information should be obtained regarding age, breed, gender, general health, and vision. Neuro-ophthalmic examination (menace, PLR, palpebral reflex) along with several diagnostic tests such as Schirmers tear test, slit lamp bio-microscopy, ophthalmoscopy, and ultrasonography are important for diagnosis of pigmentary keratitis.

Amalgamation of treatment and prevention
Till date no standard treatment has been determined. Specific therapy chosen for pigmentary keratitis depends on the aetiology. The goal of all therapies is to delay progression which in mild affected cases can be achieved by topical treatment with lubricant drugs, corticosteroids, or immunosuppressant medications.

If the pigment threatens vision or does not respond to medications then surgery (canthoplasty) may be considered to remove hair from near the cornea and to make the opening of the eyelids smaller. Superficial keratectomy is recommended in patients who are non-responsive to medical treatment which otherwise will lead to corneal vascularisation, pigmentation, and eventually blindness. The procedure involves the entire cornea or only a specific part of the cornea and postoperatively the wound is treated medically as corneal ulcer. As the pigment is likely to return and may be accompanied by post-operative scarring of the cornea, keratectomy is less preferred surgical procedure.

Lifelong love and care – vision will be spared
Timely ophthalmic examinations can help to monitor the progression of the disease. Judicious use of lubricant and immune modulator drugs can help to manage further progression of the pigment to other quadrants of cornea and thus preserve the vision of your pet.

Depending upon the thickness and the spread of the pigment, effects on vision can be minimised by ocular medication. It is easier to prevent pigment from spreading than to reduce it. You need to be regular with the medications and have patience as this is a time-consuming process. If your pet has been detected with corneal melanosis, you should know that prolonged treatment and diligent monitoring will be required to maintain their vision.

Your efforts, love, and care will surely help in the treatment and ensure a speedy and healthy recovery for your furry friend.

(Dr Beenish Qureshi, Dr Deepti Sharma and Dr Harmanpreet Singh Sodhi are research scholars from Guru Angad Dev Veterinary and Animal Sciences University (GADVASU), Ludhiana, Punjab)
Regular check-ups!
Regular ophthalmic check-ups are a must, keep an eye if your pet is constantly scratching or itching around the eyes, and see if there is any discharge from one or both eyes. Make sure to gently clean your pet’s eyes with moist cotton when you’re grooming him.

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