Eyelash

An eyelash (also called lash) (Neo-Latin: cilium, plural cilia) is one of the hairs that grows at the edges of the top and bottom eyelids, spanning outwards and away from the eyes. The lashes grow in up to six layers on each of the upper and lower eyelids. Eyelashes serve to protect the eye from debris, dust, and small particles, and are highly sensitive to touch, thus providing a warning that an object (such as an insect or lint) is near the eye, which then reflexively closes or flutters to rid the area of the object. The eyelid margin from which lashes grow is among the most sensitive parts

Trichiasis ( , ) is a medical term for abnormally positioned eyelashes that grow back toward the eye, touching the cornea or conjunctiva. This can be caused by infection, inflammation, autoimmune conditions, congenital defects, eyelid agenesis and trauma such as burns or eyelid injury.

A distichia is when cilia (eyelashes) arise from the free lid margin. This abnormality, attributed to a genetic mutation, is a common opthalmological disorder of the dog. Distichiae usually exit from the duct of the meibomian gland at the eyelid margin. They are usually multiple, and sometimes more than one arises from a duct. They can affect either the upper or lower eyelid and are usually bilateral. The lower eyelids of dogs usually have no eyelashes.

Trichomegaly is a condition in which the eyelashes are abnormally long, objectively defined as 12mm or greater in the central area and 8mm in the peripheral. The term was first used by H. Gray in 1944 in a publication in the Stanford Medical Bulletin, though he was only the third person to characterize the disorder; the first two reports were published in German in 1926 and 1931 by Reiter and Bab, respectively. Gray suggested the use of the term "movie lashes" to describe this condition, for long lashes were at the time being portrayed in film as a desirable characteristic in women.