Eyelashes, the delicate hairs bordering the eyelids, are an important component of human anatomy. They emerge from the edges of both the upper and lower eyelids, curving outwards and away from the eye. While often appreciated for their aesthetic appeal, eyelashes primarily serve a biological purpose.
Guardians of the Eye
Eyelashes function as a defense mechanism for the eyes, creating a physical barrier against various external elements. They intercept airborne particles such as dust, debris, and pollen, preventing them from entering the sensitive eye surface. These particles can cause irritation, infection, or damage to the delicate cornea and conjunctiva.
Beyond solid particles, eyelashes also shield the eyes from liquids like sweat and rain. Their curved shape helps divert moisture away from the eye, channeling it to the sides of the face. This action helps maintain clear vision and reduces irritants reaching the eye. Eyelashes also regulate the tear film, keeping the eye moist by minimizing airflow over the eyeball. This reduces tear evaporation, ensuring proper lubrication and preventing dryness.
More Than Just Protection
Eyelashes possess a sensory function, providing an additional defense for the eyes. The base of each eyelash is rich in nerve endings, making them sensitive to touch and slight movements. This sensitivity allows eyelashes to act as “feelers,” detecting approaching objects or irritants.
When an object, or a puff of air, brushes against an eyelash, it triggers a rapid, involuntary blink reflex. This swift closure of the eyelids protects the eye from harm before contact. This automatic reaction explains why it is challenging to keep eyes open when applying contact lenses or makeup.
The Eyelash Life Cycle
Eyelashes, like other body hairs, undergo a growth cycle with three phases: anagen, catagen, and telogen. The anagen, or growth phase, is when eyelashes actively grow, nourished by a blood supply. This phase typically lasts 30 to 45 days (4 to 10 weeks), with lashes growing at about 0.12 to 0.14 millimeters per day.
Following the anagen phase is the catagen, or transition phase, lasting about two to three weeks. During this period, the hair follicle shrinks, detaches from its blood supply, and the eyelash stops growing. The final stage is the telogen, or resting phase, lasting up to 100 days (three to four months). In this phase, the old eyelash rests before shedding to make way for new growth, ensuring continuous renewal. The entire cycle ranges from four to eleven months.