Affects: Dogs
Ocular melanosis (OM) is a blue-gray and/or brown lesion of the conjunctiva that can be separated into benign conjunctival epithelial melanosis (BCEM) and primary acquired melanosis (PAM), of which the latter is considered a risk factor for uveal melanoma. The disease is caused by an increase of melanocytes in the iris, choroid, and surrounding structures. Overproduction of pigment by these cells can block the trabecular meshwork through which fluid drains from the eye. The increased fluid in the eye leads to increased pressure, which can lead to glaucoma. In humans, this is sometimes known as pigment dispersion syndrome.
Diagnosis: Usually unilateral, flat, patchy, pigmented area that involves the limbus (the border of the cornea and sclera) and interpalpebral (between the eyelids) conjunctiva.
Slit-lamp examination.
Histopathological examination that shows intraepithelial proliferation of conjunctival epithelial melanocytes.
Treatment: There are a few management and treatment strategies for PAM. When lesions are small, they can be carefully watched on an annual basis. It is important to compare pictures year to year. However, for medium and large-sized lesions, we can consider surgery (excisional vs incisional biopsy), chemotherapy, or cryotherapy.
When a patient has PAM with atypia, an excisional biopsy with cryotherapy is recommended as the treatment. For some patients with diffuse lesions, surgery is not an option. In these cases, the recommendation is cryotherapy in combination with topical mitomycin C, which is a chemotherapeutic agent.