October Pulse Article (PART 4 OF 12, COMMON SMALL ANIMAL THIRD EYELID ABNORMALITIES)

Ophthalmic presentations are not uncommonly associated with the tissues of one or both third eyelids. These structures are contiguous with their overlying conjunctival surfaces and as a consequence may also be affected by inflammatory and immune-mediated surface conditions, including allergic & follicular conjunctivitis & (less typical) chronic superficial keratitis (“pannus”).

Symblepharon describes varying degrees of adhesion which may occur between adjacent conjunctival surfaces (including palpebral and/or third eyelid surfaces) and/or the cornea. Symblepharon results from loss of epithelial continuity, most commonly arising secondary to feline herpesviral disease in young animals but potentially arising secondary to any severe feline or canine conjunctival inflammation Surgical resection of conjunctival adhesions is relatively straightforward, however the tendency for the aggressive (potentially aggravated) reformation of these adhesions is extremely high and as a consequence surgical resection is rarely indicated.

The third eyelid is supported by a “T-shaped” cartilaginous structure, which may occasionally be malformed, resulting in bending or “scrolling” of the leading edge of the third eyelid. This condition is generally congenital and may be unilateral or bilateral.  Secondary conjunctivitis typically results, the Great Dane being relatively commonly affected.  When indicated, treatment comprises the surgical resection of malformed cartilage. In skilled hands the prognosis for repair is excellent.

Prolapse of the lacrimal gland of the third eyelid (“cherry eye”) is relatively common, particularly in young patients. Presentation may be unilateral or bilateral. This condition results from defective connective tissue development in predisposed breeds, notably the English Bulldog. The excision of prolapsed glandular tissue should always be avoided where possible, in order to avoid subsequent complications (particularly KCS). The ideal treatment represents careful & accurate surgical repositioning of prolapsed tissue.

Keratoconjunctivitis sicca (“dry eye”) may represent a qualitative deficiency resulting from insufficient lipid and/or mucous secretion and/or a quantitative deficiency arising secondary to insufficient lacrimal glandular secretions. Lacrimal glandular dysfunction may arise secondary immune-mediated, traumatic, inflammatory, toxic or neurological etiologies. Pharmacological agents with the potential to cause or exacerbate KCS include the sulpha-containing anti-microbial compounds, making them a poor choice in patients affected by KCS. Commonly affected breeds include the West Highland White Terrier & English Bulldog. Treatment typically comprises a combination of lacrimostimulant and/or anti-inflammatory agents and long-term therapy is typically necessary in order maintain patients in a comfortable & disease-free state.  The adjunctive administration of oral pilocarpine may additionally help to re-establish function in cases associated with neurologic dysfunction. Secondary eyelid and/or meibomian gland inflammation/infection should be addressed where present and & ruling out underlying endocrinopathies is also advocated.

Finally, the glandular tissues of the third eyelid may be affected by a variety of neoplastic processes. Relatively common tumors in this location include the vascular neoplasms (haemangioma/haemangiosarcoma), squamous cell carcinoma (particularly in white or minimally pigmented patients), lymphoma, melanoma, and glandular adenomas/adenocarcinomas. The management of each tumor type is beyond the scope of this brief clinical review however typically encompasses excision where possible in combination with adjunctive radio/chemo therapy where indicated &/or the involvement of a veterinary oncologist. The defined presence of malignant neoplasia represents an appropriate indication for third eyelid excision (partial or total) despite the potential for complications, which may ensue.

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 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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