Download Pigmentary Keratitis

Pigmentary Keratitis
Rhea V. Morgan, DVM, DACVIM (Small Animal), DACVO
BASIC INFORMATION
Description
Pigmentary keratitis is the migration of brown (melanin) pigment
into the cornea. The pigment usually affects the surface of the cornea, and one or both eyes may be involved. The pigment may or
may not be accompanied by inflammation. Pigmentary keratitis
occurs most often in the dog; it is rare in cats.
Causes
Pigment usually invades the cornea as a result of chronic irritation.
Causes of irritation include the following:
• Extra or abnormal eyelashes or hair rubbing on the cornea
• Exposure of the cornea in dogs with prominent eyes and large
eyelid openings, especially in the flat-faced breeds of dogs
• Dry eye (keratoconjunctivitis sicca) from lack of tear
production
• Inability of the eyelids to protect the eye because of decreased
blinking or enlargement of the eye from glaucoma
• Corneal ulceration
• Chronic corneal inflammation (keratitis), such as pannus in the
dog
Clinical Signs
Depending on the underlying cause, the dog may show no clinical
signs except for the development of a dark brown film on the eye.
This film may cover only a small portion of the cornea and only
be detected by your veterinarian during an examination. If the pigment progresses to cover most of the cornea, then decreased vision
may be noted. Other signs usually pertain to the underlying cause
and can include pain; tearing; increased thick, ropey discharge;
enlargement of the eye; redness; and other ocular symptoms.
Diagnostic Tests
The presence of corneal pigment is confirmed by examination
of the eye, often with the use of magnification. Other diagnostic
tests, such as tear testing, fluorescein staining, and glaucoma testing, are used to determine the underlying cause. The eyelids, blink
responses, and position and shape of the eye are also thoroughly
examined.
TREATMENT AND FOLLOW-UP
Treatment Options
The first priority of treatment is to correct any underlying causes.
Eyelid abnormalities and extra eyelashes may require surgery.
Medications for dry eye, pannus, and glaucoma are started when
indicated.
If the pigment is present in one of the flat-faced breeds of dog
and is secondary to the typical anatomy of these breeds (large, prominent eye; lashes or hair growing near the eye; large eyelid opening),
then conservative therapy with topical lubricants may be started.
• If the pigment affects the central cornea or progressively worsens, then prolonged therapy with cyclosporine or tacrolimus
may be helpful. These drugs increase tear production and
encourage the pigment to thin and disperse over time.
• If the pigment threatens vision or does not respond to medications in these breeds, then surgery (canthoplasty) may be considered to remove hair from near the cornea and to make the
opening of the eyelids smaller.
• Surgery to remove the pigment from the cornea is no longer performed in most cases, because the pigment is likely to return and
may be accompanied by postoperative scarring of the cornea.
Follow-up Care
Periodic recheck visits are used to monitor both the pigmentation and the underlying cause. If the pigmentation visibly worsens
despite therapy or any new signs develop, notify your veterinarian.
Following re-examination, the frequency or types of medications
may be changed.
Prognosis
It is easier to prevent pigment from spreading than it is to make it
recede. When pigment does recede, the process can be slow and
take many months. Stopping the progression of the pigment often
depends on whether the underlying condition can be successfully
treated. If the pigment does not cover the pupil or is not very thick,
it may have minimal effects on vision. Thick, widespread pigmentation can result in blindness. Prolonged treatment and diligent
monitoring may be required for the life of the dog.
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