Trichiasis is a medical term for abnormally positioned eyelash

Eyelash

An eyelash or simply lash is one of the hairs that grow at the edge of the eyelid. Eyelashes protect the eye from debris and perform some of the same function as whiskers do on a cat or a mouse in the sense that they are sensitive to being touched, thus providing a warning that an object is near...

es that grow back toward the eye, touching the cornea or conjunctiva. This can be caused by infection

Infection

An infection is the colonization of a host organism by parasite species. Infecting parasites seek to use the host's resources to reproduce, often resulting in disease...

, inflammation

Inflammation

Inflammation is part of the complex biological response of vascular tissues to harmful stimuli, such as pathogens, damaged cells, or irritants. Inflammation is a protective attempt by the organism to remove the injurious stimuli and to initiate the healing process...

, autoimmune conditions, congenital defects, eyelid agenesis and trauma

Physical trauma

Trauma refers to "a body wound or shock produced by sudden physical injury, as from violence or accident." It can also be described as "a physical wound or injury, such as a fracture or blow." Major trauma can result in secondary complications such as circulatory shock, respiratory failure and death...

 such as burns or eyelid injury.

Standard treatment involves removal or destruction of the affected eyelashes with electrology

Electrology

Electrology is the practice of electrical epilation to permanently remove human hair. The actual process of removing the hair is referred to as electrolysis.-Overview:...

, specialized laser

Laser

A laser is a device that emits light through a process of optical amplification based on the stimulated emission of photons. The term "laser" originated as an acronym for Light Amplification by Stimulated Emission of Radiation...

, or surgery

Surgery

Surgery is an ancient medical specialty that uses operative manual and instrumental techniques on a patient to investigate and/or treat a pathological condition such as disease or injury, or to help improve bodily function or appearance.An act of performing surgery may be called a surgical...

. In many cases, removal of the affected eyelashes with forceps resolves the symptoms, although the problem often recurs in a few weeks when the eyelashes regrow. Severe cases may cause scarring of the cornea and lead to vision loss if untreated. Mild cases may not require treatment.

Trichiasis in dog

Dog

The domestic dog is a domesticated form of the gray wolf, a member of the Canidae family of the order Carnivora. The term is used for both feral and pet varieties. The dog may have been the first animal to be domesticated, and has been the most widely kept working, hunting, and companion animal in...

s is hair from the eyelid growing in the wrong direction and rubbing on the eye, causing irritation. It usually occurs at the lateral upper eyelid, especially in the English Cocker Spaniel

English Cocker Spaniel

The English Cocker Spaniel is a breed of gun dog. The English Cocker Spaniel is an active, good-natured, sporting dog, standing well up at the withers and compactly built. There are "field" or "working" cockers and "show" cockers...

. Trichiasis also refers to hair from a nasal fold rubbing on the eye. This type of trichiasis can be flattened by rubbing petroleum jelly

Petroleum jelly

Petroleum jelly, petrolatum, white petrolatum or soft paraffin, CAS number 8009-03-8, is a semi-solid mixture of hydrocarbons , originally promoted as a topical ointment for its healing properties...

onto it, but surgery is sometimes necessary for permanent correction.