Distichiasis is the medical term for “double eyelashes,” a rare abnormality involving the growth of a second row of lashes. This second row can range from a single extra hair to a complete additional set. The condition originates from an abnormal biological development within the eyelid structure. Whether present from birth or acquired later in life, Distichiasis can lead to various ocular complications, often requiring careful identification and intervention.
Distichiasis: The Medical Condition and Causes
Distichiasis is defined by the abnormal sprouting of eyelashes from the orifices of the Meibomian glands, rather than from the normal hair follicles along the eyelid margin. Meibomian glands are specialized sebaceous glands that secrete the oily component of the tear film. A developmental error occurs because the cells forming these glands share a common embryonic origin with hair follicles, allowing the glands to transform into a unit capable of producing hair. The condition is categorized into two primary types: congenital and acquired.
Congenital Distichiasis
The congenital form is present at birth and is often hereditary, frequently linked to a mutation in the FOXC2 gene on chromosome 16. This gene is involved in the development of the lymphatic and vascular systems. Its mutation causes Lymphedema-Distichiasis Syndrome (LDS) in most affected individuals. LDS is an autosomal dominant disorder characterized by double eyelashes and lymphedema, which is the accumulation of fluid, usually in the limbs.
Acquired Distichiasis
Acquired Distichiasis develops later in life and results from chronic inflammation, injury, or scarring of the eyelid margin. Conditions that cause long-term inflammation, such as ocular cicatricial pemphigoid, chronic blepharitis, or chemical burns, can induce the Meibomian glands to undergo metaplasia. This process causes the gland structure to change, leading to the growth of hair shafts where they normally would not exist. The acquired lashes tend to be shorter, finer, and less pigmented than the normal lashes, and the extent of the condition often correlates with the severity of the underlying inflammatory disease.
Ocular Complications and Symptoms
Some individuals with Distichiasis experience no symptoms, but others face functional consequences when the extra lashes grow inward toward the eye’s surface. The second row of lashes can rub directly against the cornea and conjunctiva, creating a persistent foreign body sensation. This mechanical friction often leads to chronic eye irritation, excessive tearing, and redness.
The most concerning complication is potential damage to the cornea. Constant rubbing causes tiny abrasions on the corneal surface, increasing the risk of developing a serious infection called keratitis. Repeated trauma over time can lead to corneal scarring, potentially resulting in impaired vision if the scarring occurs in the central visual axis. Other symptoms include light sensitivity (photophobia) and the development of styes.
Clinical Identification and Differentiation
An ophthalmologist identifies Distichiasis through a comprehensive eye examination, most commonly using a specialized microscope called a slit lamp. This device allows the doctor to view the eyelid margin and the accessory eyelashes in high magnification, confirming they emerge from the Meibomian gland orifices.
It is necessary to differentiate Distichiasis from Trichiasis, a more common condition. In Trichiasis, the lashes originate normally but are misdirected, turning inward toward the eye. If a congenital cause is suspected, especially with lymphedema present, genetic testing for the FOXC2 mutation may be recommended to confirm Lymphedema-Distichiasis Syndrome.
Treatment and Management Pathways
Treatment for Distichiasis is generally reserved for cases that cause symptoms or pose a risk to the patient’s vision. For temporary relief of a few offending lashes, simple mechanical plucking (epilation) can be performed. However, the hair will regrow within a few weeks because the follicle remains intact.
The goal of a permanent solution is to destroy the abnormal hair follicle completely, requiring more advanced procedures. Electrolysis uses a fine needle and electric current to destroy the hair root. Cryotherapy involves freezing the tissue containing the hair follicles to destroy them and prevent regrowth. Another option is argon laser ablation, which uses focused heat energy to target and destroy the follicle.
In cases where numerous lashes are present or other treatments have failed, a minor surgical procedure may be necessary. Surgical excision involves splitting the eyelid margin to access and remove the offending hair follicles and surrounding tissue directly. Surgical excision often yields better outcomes than blind destruction methods like cryotherapy or electroepilation, which may have success rates around 50 to 60 percent in acquired cases.