Distichiasis is a condition where eyelashes emerge from the meibomian glands in the centre of the eyelid. These glands do not normally produce hairs. These "extra" eyelashes often rub on the surface of the eye and may cause irritation. Distichiasis tends to run in genetic lines of dogs, and is most commonly found in Staffordshire Bull terriers, American Cocker Spaniels, Shih-Tzus Tibetan Spaniels and Poodles.

The severity of the problem and the needs 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 many eyelids. Although some patients live their entire lives without being bothered by their distichia, others require medical or surgical treatment to alleviate irritation caused by the hairs rubbing on the cornea.

Signs of 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: redness, squinting, discharge, or rubbing at the eye. Since corneal ulcers can also occur in patients that have no distichiasis, it can sometimes make determining the significance of the distichiasis difficult. The location of the ulcer and the distichia help us decide whether the distichia are the underlying cause of the ulcer.

Temporary relief may be provided by pulling out the abnormal hair in the exam room, but these lashes almost always grow back. Topical ointments may be used to help lubricate the eye and protect it from the hair. If clinical signs persist, cryosurgery can be used to treat distichiasis. A liquid nitrogen or nitrous oxide probe is applied to the eyelid to kill the hair producing cells in the base of each Meibomian gland follicle and prevent the distichia from growing back.

Although cryosurgery will prevent the distichia from growing back in the same area, there are about sixty places along each lid where 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 areas on the eyelids.