Cherry eye is clinically defined as a prolapsed gland of the third eyelid. The term cherry eye was coined because the prolapsed gland looks like a cherry located near the medial canthus. The gland, which under normal circumstances hugs the base of the T-cartilage in the third eyelid and sits adjacent to the orbital rim, becomes obvious to the owner after prolapse.
Breed and Age. Cherry eye can occur in many breeds of dogs but is most common in young cocker spaniels, Lhasa apsos, Shih Tzus, bulldogs, mastiffs, beagles, shar-peis, Pekingese, Boston terriers, and St. Bernards.1 It is much less common in cats, but it occasionally occurs in Burmese, Siamese, and Persians. Although the problem can occur at any age, it is most common in animals 2 years of age or younger and can be unilateral or bilateral at initial presentation. Very young puppies often present with a prolapsed gland.
Genetic Implications. Although the precise mechanism by which cherry eye is inherited is unknown, the breed predisposition implies some type of genetic mechanism. The Canine Eye Registration Foundation, the national purebred eye registry, does not define the genetics of the problem and advises "breeder option" for breeding purposes, meaning that the actual inherited mechanism is unknown, but that the problem frequently occurs in that particular breed. As it occurs almost exclusively in Burmese, Siamese, and Persian cats, the problem is probably genetic in cats as well.
The anatomical structures that anchor the gland of the third eyelid in its normal position and the pathogenesis of their failure are poorly understood. The gland is classified as seromucoid in dogs and contributes an estimated 30% to 57% to aqueous tear production.1,2 It has recently been shown that removal of the gland or leaving the prolapsed gland in situ predisposes the patient to KCS, a common complication associated with cherry eye.3 KCS requires lifelong treatment, usually with topical cyclosporine, corticosteroids, and ocular lubricants.
Appearance of a round, smooth, red mass near the medial canthus of a young dog, especially in high-risk breeds, is highly suggestive of a prolapsed gland of the third eyelid (Figure 1). Inflammation of the gland with swelling and redness may be present, but often the gland looks relatively normal, with a smooth, pink conjunctival surface. As the gland remains prolapsed for an extended period (months to years), the exposed conjunctiva overlying the gland often becomes pigmented, but there is no evidence of ocular pain. The gland usually remains prolapsed but occasionally repositions itself naturally or with gentle digital massaging. Even after repositioning, prolapse tends to recur.