"Eyelash" - what is it, definition of the term
«Eyelash» is a keratin‑based filament originating from the marginal zone of the eyelid, projecting outward to form a protective fringe that traps particulate matter, directs tear film, and reduces evaporative loss from the eye.
Detailed information
The hair that borders the ocular aperture serves as a protective barrier, filtering dust, debris and microorganisms before they reach the corneal surface. Each strand originates from a specialized follicle embedded in the skin of the eyelid, composed of keratinized cells that undergo a continuous growth‑shedding cycle lasting approximately four to six weeks. The growth phase (anagen) is followed by a brief transitional stage (catagen) and a resting phase (telogen) during which the shaft is expelled and replaced by a new filament.
Functionally, the barrier reduces tear evaporation, maintains ocular surface humidity, and directs the flow of tears toward the puncta. Its curvature and spacing create a laminar airflow that deflects airborne particles. The tactile sensitivity of the follicular region triggers reflex blinking when foreign objects contact the lashes, thereby protecting the eye from mechanical injury.
Parasites that may colonize the lid hair include:
- Tick larvae that attach to the outer fringe, feeding on blood and causing localized inflammation.
- Small true bugs (e.g., Cimex species) that seek shelter among the hairs, leading to secondary bacterial infection.
- Pediculus capitis or Phthirus species that occasionally migrate to the eyelid region, resulting in itching and secondary dermatitis.
- Flea nymphs that can be incidentally transferred during grooming, producing transient irritation.
Infestations typically present with erythema, edema, and pruritus of the peri‑ocular skin. Diagnostic confirmation relies on visual identification of the organism within the hair shaft or on adjacent skin. Treatment protocols involve targeted ectoparasiticide application, careful removal of the affected hairs, and topical anti‑inflammatory agents to mitigate tissue response. Preventive measures include regular hygiene, avoidance of contaminated bedding, and routine inspection of the lid margin in individuals exposed to high‑risk environments.