December Pulse Article Available (part 6 of 12, Common Small Animal Scleral Abnormalities)

December 28, 2018

A dermoid (or “choristoma”) represents an area of normal haired skin in an abnormal location on the eye or adnexal tissue. Lesions may affect the tissues of the cornea, episclera and/or eyelids. Changes are congenital so are typically noted soon after the eyes open at 2 weeks of age. Commonly affected breeds include the German Shepherd, the Dachshund & the St Bernard.

The treatment of choice is surgical excision of the abnormal tissue. Once excised these lesions do not recur.

Primary scleritis describes a primary inflammatory disorder of the canine scleral and/or episcleral tissues, which is thought to be immune-mediated in origin. Clinically this condition presents as an inflammatory infiltrate around part or all of the corneoscleral limbus, affecting one or both eyes. Adjacent structures including the uveal tract may be involved & demonstrate clinical inflammation, extending in rare cases to necrotic scleral lesions, uveitis, retinal detachment and/or glaucoma. Commonly affected breeds include the Cocker Spaniel & Boston Terrier. Systemic screening for immune-mediated disorders may be indicated in some cases.

Treatment comprises topical and/or systemic immune-modulatory therapy using corticosteroids and or adjunctive agents such as azathioprine, chlorambucil & cyclosporine. Scleritis can typically be managed, however in most cases, ongoing therapy is required in order to maintain the patient in a disease-free state.

Nodular granulomatous episcleritis (NGE) describes a proliferative inflammatory disorder of the canine scleral and/or episcleral tissues, which is thought be immune-mediated in origin.

Multiple terms have been used to describe this condition, including; nodular fasciitis, fibrous histiocytoma, pseudotumor & collie-granuloma. Clinically, affected patients display one or more smooth, firm, mass(es) affecting the corneoscleral limbus of one or both eyes, arising most commonly in the superior-temporal region. Commonly affected breeds include the Collie-breeds, Spaniel-breeds & Terrier-breeds. The diagnosis of NGE may be confirmed where indicated by tissue biopsy & histopathology, which typically reveals a proliferation of fibroslasts and a significant infiltration of lymphocytes, plasma cells & histiocytes. Treatment comprises topical and/or systemic immune-modulatory therapy using corticosteroids and or adjunctive agents such as azathioprine, chlorambucil & cyclosporine. In severe cases, lesions may initially be managed by the injection of repository corticosteroids, surgical resection, cryotherapy &/or the application of B-irradiation. NGE can typically be managed, however in most cases, ongoing therapy is required in order to maintain the patient in a disease-free state.

Multiple neoplastic processes may affect the scleral & episcleral tissues, notably melanocytoma/melanoma, haemangioma/haemangiosarcoma, lymphoma and squamous cell carcinoma.  

Limbal (“epibulbar”) melanocytomasare the mostfrequently encountered and may affect dogs or cats.  In rare instances, these lesions may display malignant characteristics including significant anaplasia and/or metastasis. Lesions typically present as well defined, raised and pigmented masses with a smooth surface. Progressive enlargement typically results in corneoscleral and/or intraocular invasion and may ultimately lead to glaucoma and/or retinal detachment. Limbal melanocytomas should be differentiated from extension of more malignant uveal melanomas. Commonly affected breeds include the Labrador Retriever, Golden Retriever and German Shepherd. The diagnosis of melanocytoma is made based on clinical findings, supported by histopathology, following incisional or excisional biopsy. These lesions are typically relatively benign and frequently appear to be localized to ocular tissues only. Nevertheless, the evaluation of systemic health and/or involvement via local lymph node aspiration, three-view radiography and CBC/chemistry analysis, is prudent. Treatment typically encompasses surgical resection where possible (with or without adjunctive tectonic grafting procedures). Pigment-rich melanocytomas are also relatively susceptible to the application of cryotherapy.  The prognosis for successful management of most cases is good.

Dr Esson is a board-certified veterinary ophthalmologist with more than twenty years of clinical experience and multiple areas of interest & expertise. His clinic Veterinary Ophthalmic Consulting (www.veterinaryophthalmicconsulting.com) is family owned & operated and he takes great pride & pleasure in working closely with his friends and colleagues in the greater Southern California veterinary community.

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