Double eyelashes, a rare condition medically known as Distichiasis, is characterized by the presence of an extra row of eyelashes emerging from the eyelids. This phenomenon is estimated to affect about one in 10,000 people. The presence of these additional lashes is a result of a developmental anomaly where hair follicles grow in a location not typically meant for eyelashes. The second row of lashes can occur on the upper or lower eyelids, or both, and is a distinctive feature of the eye margin.
The Visual Characteristics of Double Eyelashes
The visual presentation of double eyelashes is defined by the placement of the secondary row, which emerges from the openings of the meibomian glands, located slightly behind the normal row of lashes on the eyelid margin. These glands typically secrete oils that help lubricate the eye, but in Distichiasis, they have undergone a metaplastic transition. This means the second set of lashes sprouts from the “wet” inner edge of the eyelid, rather than the “dry” outer edge where the primary lashes grow.
The appearance of the extra lashes, or distichiae, can vary significantly among individuals. The secondary row may consist of a single stray hair, a small cluster, or a complete second set extending across the entire eyelid. Often, the accessory lashes are visually distinct from the primary row, typically being shorter, finer, and less pigmented.
The direction of growth is also a defining visual characteristic; the second row frequently grows inward toward the eye’s surface, which leads to potential symptoms. In contrast, the main set of lashes curves naturally outward.
Distichiasis: Causes and Types
The underlying cause of double eyelashes separates the condition into two main types: congenital and acquired.
Congenital Distichiasis
Congenital distichiasis is present from birth and is primarily genetic in origin, often linked to an abnormal development of the meibomian glands during fetal growth. This form is typically associated with an autosomal dominant mutation in the FOXC2 gene on chromosome 16. The FOXC2 gene plays a role in the development of the lymphatic and vascular systems, and its mutation causes epithelial cells near the eyelid margin to incorrectly differentiate into hair follicle units. Congenital distichiasis is a hallmark feature of Lymphedema-Distichiasis Syndrome (LDS), a rare genetic disorder that combines the extra row of lashes with lymphedema. However, the condition can also occur in isolation, without systemic associations.
Acquired Distichiasis
Acquired distichiasis develops later in life and is less common than the congenital form. This type is typically a secondary result of chronic inflammation, scarring, or injury to the eyelid margin. Common causes include chronic blepharitis or rare autoimmune disorders such as ocular cicatricial pemphigoid. Damage from chemical exposure or meibomian gland dysfunction can also trigger the metaplastic change that leads to the growth of new hair follicles.
Associated Symptoms and Potential Complications
While many individuals with double eyelashes experience no symptoms, the condition becomes medically significant when the extra lashes are misdirected or coarse. When the distichiae rub against the delicate ocular surface, they can cause a chronic foreign body sensation. This constant irritation often leads to symptoms like redness, swelling, and excessive tearing as the eye attempts to flush out the irritant.
The mechanical friction caused by the rubbing lashes can lead to more serious complications affecting the cornea. Persistent contact can result in superficial punctate keratitis or more severe corneal abrasions. In the most severe instances, this constant damage can cause corneal ulceration or scarring, which carries a risk of vision impairment. The irritation also increases the risk of recurrent infections, such as conjunctivitis or styes.
Management and Treatment Options
Treatment for double eyelashes is only necessary when the distichiae cause symptoms or threaten the health of the eye. For mild cases, management begins with conservative measures, such as using lubricating eye drops or ointments to protect the ocular surface from friction. When symptoms persist, the goal shifts to permanent removal of the offending lashes and their follicles.
A temporary method is simple epilation, or plucking the lashes with forceps, which provides immediate relief. However, the hair follicle remains intact, and the lashes typically regrow within two to three weeks, necessitating repeated treatments. More definitive solutions aim to permanently destroy the hair follicle:
- Electrolysis, which uses an electric current to ablate the follicle.
- Cryotherapy, which involves freezing the tissue to destroy the hair root.
- Laser thermal ablation, using devices like an argon laser, is also employed to target and destroy the individual lash follicles.
- Surgical excision techniques, such as lid splitting with removal of the follicle, or marginal tarsectomy, may be performed for extensive cases or when non-surgical methods fail.