Distichiasis is a condition where eyelashes emerge from the ducts of glands within the eyelid (Meibomian gland) which does not normally produce hairs. These "extra" eyelashes often rub on the surface of the eye and may cause irritation. Distichiasis is considered to be a breed-related problem in dogs, and is most commonly found in retrievers, spaniels, poodles, Shih Tzus and Weimeranas.

The severity of the problem and the need for treatment vary from patient to patient. Some patients may have only a few distichia (abnormal hairs) on a single eyelid, while others may have several distichia present on all four eyelids. Although some patients live their entire lives without being bothered by their distichia (common in the American Cocker Spaniel), others require medical or surgical treatment to alleviate irritation caused by the hairs rubbing on the cornea.

Signs that a patient may be bothered by distichiasis include: redness, squinting, discharge, or rubbing at the eye. Sometimes distichiasis can cause corneal ulcers or erosions where the hairs touch the surface of the eye. Clinical signs of corneal ulcers are similar to those of distichiasis.

  
Temporary relief may be provided by pulling out the abnormal hair in the exam room, but these lashes usually grow back. Topical ointments may be used to help lubricate the eye and protect it from the hair. If clinical signs persist, one of two different surgical procedures can be used to treat distichiasis. Electroepilation involves applying heat to the eyelid to destroy the hair follicles. Cryosurgery involves freezing the lid and follicles. Both procedures destroy the hair follicle and serve to prevent the distichia from growing back.

Although surgery usually prevents the distichia from growing back in the same area, new distichia could potentially emerge. Therefore, while surgery fixes the immediate problem, it is possible that the patient could have a future distichiasis problem if new distichia grow from other follicles in the eyelids.