Most people have one single row of eyelashes along the margin of both the upper and lower eyelids. This single row is the standard anatomical feature for the vast majority of the population. However, some individuals possess additional rows, a condition that is considered a dermatological anomaly. The presence of a second row, whether complete or partial, is a variation that can range from a harmless trait to a source of significant eye irritation.
The Normal Eyelash Structure
Eyelashes are specialized, short hairs that emerge from the eyelid margin, following a precise biological cycle. The upper eyelid typically hosts between 90 and 160 lashes, while the lower eyelid has significantly fewer, usually ranging from 75 to 80 lashes. Both are positioned in a single line.
The growth cycle has three phases. The anagen phase is the active growth period, lasting approximately four to six weeks. Next is the catagen phase, a transitional period of two to three weeks where the hair stops growing and the follicle shrinks. The final stage is the telogen phase, a resting period that can last up to four months before the old lash sheds and the cycle begins anew.
What Causes Extra Rows of Eyelashes
The growth of a second row of eyelashes is a condition known as Distichiasis. This anomaly involves extra lashes growing from the meibomian glands, which are oil-producing glands located on the inner edge of the eyelid, rather than from the typical hair follicles. The additional lashes can appear as a full second line, a small cluster of hairs, or even just a single extra lash.
Distichiasis is most often a congenital condition, meaning it is present from birth and is typically inherited through a genetic mutation. The condition can also be acquired later in life due to chronic inflammation or scarring of the eyelid margin. Causes include long-term blepharitis, chemical injury, or a rare autoimmune disorder.
The extra lashes are often thinner, shorter, and softer than normal, sometimes growing inward toward the eye. When these abnormal lashes touch the surface of the eye, they can cause irritation, a gritty feeling, excessive tearing, and light sensitivity. This friction can lead to chronic eye redness and inflammation, sometimes necessitating medical attention to prevent damage to the cornea.
The Function of Eyelashes
The primary biological purpose of eyelashes is to serve as a physical protective barrier for the eye. They are positioned to catch airborne particles, such as dust, debris, and sweat, before they enter the sensitive eye area. They also help regulate airflow across the eye’s surface, reducing the evaporation of the tear film necessary for lubrication.
Eyelashes also serve a sensory role. The hair follicles at the base of the lashes are highly sensitive, equipped with many nerve endings. Even the lightest touch triggers an immediate, reflexive blink. This rapid response acts as an early warning system, protecting the eye from foreign objects before direct contact occurs.
Managing Abnormal Eyelash Growth
When extra lashes from Distichiasis irritate the eye, medical intervention is necessary to manage discomfort and prevent damage. For a few stray lashes, temporary removal through epilation, or plucking, provides immediate relief. However, the lashes will regrow since the follicle remains intact.
For a lasting solution, ophthalmologists use techniques aimed at destroying the hair follicle to prevent regrowth. Individuals experiencing chronic eye irritation should consult an eye specialist to determine the safest method of management.
Permanent Follicle Removal Methods
- Electrolysis, which uses an electric current.
- Cryotherapy, which freezes the follicle.
- Laser ablation, which targets and eliminates the hair root.